Using Light (Sunlight, Blue Light & Red Light) to Optimize Health

安德鲁·休伯曼：

Welcome to the Huberman Lab 播客, where 我们 discuss science 和 science-based tools 对于 everyday life.

安德鲁·休伯曼：

I'm Andrew Huberman 和 I'm a professor of 神经生物学 和 ophthalmology at Stanford School of Medicine. Today 我们 are going to discuss light 和 the many powerful uses of light to optimize 我们的 health. 我们're going to discuss the use of light 对于 optimizing 皮肤 health, appearance 和 longevity, 对于 wound healing, 对于 optimizing 激素 balance, 和 对于 regulating sleep, alertness, 情绪, 和 even 对于 offsetting dementia.

安德鲁·休伯曼：

一 of the reasons why light has such powerful effects on so many 不同的 aspects of 我们的 biology is 那 it 可以 be translated 进入 electrical signals in 我们的 大脑和身体, 进入 激素 signals in 我们的 大脑和身体, 和, indeed, 进入 what 我们 call cascades of biological 通路, meaning light 可以 actually change the genes 那 the cells of 你的 身体 express, 和 那 is true throughout the lifespan.

安德鲁·休伯曼：

Today, I 会 discuss the mechanisms by which all of 那 occurs. I promise to make it clear 对于 那些 of 你 那 don't have a biology background, 和 if 你 do have a biology background, I'll try 和 provide sufficient depth so 那 it's still of interest to 你. 和 I promise to give 你 tools, 非常 具体的 方案 那 are extracted 从 the peer-review literature 那 会 allow 你 to use 不同的 so-called wavelengths, which most of us think of as colors, of light in order to modulate 你的 health in the ways 那 are most 重要 to 你.

安德鲁·休伯曼：

对于 那些 of 你 那 are thinking 那 the use of light to modulate health falls under the category of woo science, pseudoscience 或 biohacking, well, nothing could be further 从 the truth. In fact, in 1903, the Nobel Prize was given to Niels Finsen. He was Icelandic; he lived in Denmark 对于 the use of phototherapy 对于 the treatment of lupus. So there's 更多 than a hundred years of quality science emphasizing the use of light, 和 as 你'll soon see, the use of particular wavelengths, 或 colors of light, in order to modulate the activity of cells in the 大脑和身体.

安德鲁·休伯曼：

So while it is the case 那 many places 和 companies are selling therapies 和 products related to the use of flashing lights 和 colored lights, promising 具体的 outcomes 从 everything 从 stem cell renewal to improvement of 大脑 function, 和 some of 那些 don't have any basis in science, there are phototherapies 那 do have a strong foundation in quality science, 和 那些 are the 研究 和 the 方案 那 我们 are going to discuss today.

安德鲁·休伯曼：

但 I thought 那 人们 可能 appreciate knowing 那 over a hundred years ago, 人们 were thinking 关于 the use of light 对于 the treatment of various diseases 和 then 对于 improving health. 和 indeed, many of 那些 therapies are used today in high-quality hospitals 和 研究 institutions, 和 of course, clinics 和 homes 大约 the world.

安德鲁·休伯曼：

一 of the 更多 exciting examples of phototherapy in the last few years is the beautiful work of Dr. Glen Jeffery, at University College London. The Jeffery Lab is known 对于 doing pioneering 和 非常 rigorous 研究 in the realm of visual neuroscience. In the last decade 或 so, they turned their 注意力 to exploring the role of red-light therapy 对于 offsetting age-related vision loss. What they discovered is 那 just brief exposures to red light early in the 天 可以 offset much of the vision loss 那 occurs in 人们 40 years 或 older. What's remarkable 关于 这些 研究 is 那 the entire duration of the therapy is just 一 to 三 分钟 done just a few times per 周.

安德鲁·休伯曼：

What's even 更多 exciting is 那 they understand the mechanism by which 这 occurred. The cells in the back of the eye 那 convert light information 进入 electrical signals 那 the rest of the 大脑 可以 understand 和 create visual images 从, well, 那些 cells are extremely metabolically active. They need a lot of ATP, 或 能量, 和 as 我们 age, 那些 cells get 更少 efficient at creating 那 ATP 和 能量. Exposure to red light early in the 天, 和 it does have to be early in the 天, allowed 那些 cells to replenish the mechanisms by which they create ATP.

安德鲁·休伯曼：

I'll talk 关于 这些 experiments in 更多 detail later in the episode, 和 the 方案 so 那 你 could apply 那些 方案 应该 你 choose. 但 I use 这 as an example of 我们的 growing understanding of not just 那 phototherapies work, 但 how they work. 和 it is 通过 the linking of 方案 和 mechanism 那 我们, meaning all of us, 可以 start to apply phototherapies in a rational, safe 和 powerful way.

安德鲁·休伯曼：

之前 I begin, I'd like to emphasize 那 这 podcast is separate 从 my teaching 和 研究 roles at Stanford. It is 然而 part of my desire 和 effort to bring zero-cost-to-consumer information 关于 science 和 science-related tools to the general public. In keeping 与 那 theme, I'd like to thank the sponsors of today's podcast.

安德鲁·休伯曼：

Okay, let's talk 关于 light. 首先, I want to talk 关于 the physics of light, 和 I promise to make 那 非常 clear even if 你 don't have a background in physics. 和 then I want to talk 关于 the biology of light, meaning how light is converted 进入 signals 那 你的 大脑和身体 可以 use to impact things like organ health 或 disease, 或 how 你 可以 use light in order to repair particular organs like 你的 皮肤, 你的 eyes, 你的 大脑, et cetera.

安德鲁·休伯曼：

The physics of light 可以 be made 非常 simple by just illustrating a few key bullet points. The 首先 bullet point is 那 light is electromagnetic 能量. If the word electromagnetic feels daunting to 你, well then just discard 那 和 just think of light as 能量 和 think of 能量 as something 那 可以 impact other things in its environment. Now, the way to imagine light 或 to conceptualize light as 能量 is 那 all 大约 你, light is traveling in 这些 little wavelengths. 和 the reason — 对于 那些 of 你 那 are watching — I'm making a little wavy motion 与 my hand is 那's actually the way 那 light 能量 moves in little waves. Just like sound waves are coming at 你 和 impinging on 你的 ears, if 你 可以 hear me talking right now, 那 is happening, 那些 are sound waves, meaning the movement of 空气 particles out there impacting 你的 ear drum. Well, light 能量 is just little bits of electromagnetic 能量 traveling 通过 你的 environment all the time in 这些 little waves 和 impinging on 你的 大脑和身体 和 eyes, et cetera.

安德鲁·休伯曼：

As I mentioned 之前, 能量 可以 change the way 那 other things behave. It 可以 cause reactions in cells of 你的 身体. It 可以 cause reactions in fruit, 对于 instance, right? 你 see a piece of fruit 和 it's not ripe, 但 it gets a lot of sunlight 和 it ripens. 那's 因为 the electromagnetic 能量 of sunlight had an impact on 那 plant 或 那 tree 或 even on the fruit directly.

安德鲁·休伯曼：

As a parallel example of 能量 和 its ability to impact other things, 我们 are all familiar 与 food 和 the fact 那 food has calories. Calorie is a measure of 能量. It has everything to do 与 how much 热 is generated when 你 burn a particular article of food, believe it 或 not. 和 it turns out 那 how hot a given article of food burns gives 你 a sense of how much 能量 it 可以 provide 你的 身体 in terms of 你的 身体's ability to store 或 use 那 能量. So again, think of light as electromagnetic 能量, 但 确实 put 那 word 能量 进入 capital letters, embed 那 in 你的 心智 going forward, 和 你'll understand most of the 首先 bullet point of what light is in terms of the physics of light.

安德鲁·休伯曼：

Now, the 秒 thing 那 你 need to understand 关于 the physics of light is 那 light has many 不同的 wavelengths. 和 the simplest way to conceptualize 这 is to imagine 那 cover of 那 Pink Floyd album where there's a prism. 你 have a white beam of light going 进入 那 prism, 和 then the prism splits 那 beam of light 进入 what looks like a rainbow. So 你've got 你的 reds, 你的 orange, 你的 greens, 你的 blues, 你的 purples, et cetera. Anytime 我们 have light in 我们的 environment 那 is so called white light, it includes all 那些 wavelengths. 但 sunlight 和 other forms of light also have other wavelengths of light 那 我们 可以't see. So when 我们 think 关于 the rainbow, 那's just the visible spectrum of light. There are also wavelengths of light 那 are not visible to us, 但 那 are visible to some other animals, 和 那 可以 still impact 你的 大脑和身体 因为 there is still 能量 at 那些 wavelengths.

安德鲁·休伯曼：

I'll give a few examples of 这. Humans are not a species 那 可以 see 进入 the infrared realm of the spectrum. A pit viper, meaning a snake, 那 has infrared sensors, 然而, 可以 sense in the infrared. So if 你 were to walk 通过 a jungle 和 there's a pit viper there, it sees 你 as a cloud of 热 emission 因为 你的 身体 is emitting infrared 能量 all the time. 你're casting off infrared 能量. The snake 可以 see it. 你 可以't. If 你 were to put on a particular set of goggles 那 were infrared goggles, well then 你 会 be able to see the 热 emissions of any organism, human 或 otherwise, 那 could emit infrared 能量.

安德鲁·休伯曼：

Let's take the opposite end of the spectrum. 我们 are familiar 与 seeing things 那 are blue 或 green 或 非常 pale blue, 但 as 我们 say, below 那, meaning even shorter wavelength light, is out there. Ultraviolet light is a 确实 good example of light 能量 那's coming 从 the sun 和 is in 我们的 environment 和 is being reflected off surfaces all the time. 我们 don't see it 和 yet if it's 非常 bright outside, 那 ultraviolet light 可以 burn 我们的 皮肤. As 你'll learn in today's episode, ultraviolet light 可以 also positively impact us. In fact, I 会 describe a particular set of new 结果 那 show 那 ultraviolet light viewed 对于 just a few 分钟 each 天 或 landing on the 皮肤 对于 just a few 分钟 each 天 可以 actually offset a lot of pain. It actually has the ability to 减少 the amount of pain sensed by 你的 身体, 和 我们 now understand the 具体的 回路 in the 大脑和身体 那 allow 那 to happen. I'll talk 关于 那 和 the related 方案 a little bit later.

安德鲁·休伯曼：

So the 重要 thing to understand 关于 the physics of light is 那 there's 能量 at all 这些 不同的 wavelengths. 我们 only see some of 那些 wavelengths, which basically is to say 那 light impacts us at many 不同的 水平. The so-called 水平 那 I'm referring to are the 不同的 wavelengths of light. 和 你 are welcome to think of the 不同的 wavelengths of light as 不同的 colors, 但 do understand 那 there are truly colors of light 那 你 和 I 可以't see 和 yet 那 have powerful impact on 你的 大脑和身体.

安德鲁·休伯曼：

Now, the third bullet point to understand 关于 the physics of light is 那 不同的 wavelengths of light, 因为 of the way 那 their wave travels, 可以 penetrate 组织 to 不同的 depths. 这 is 非常, 非常 重要. Today 我们're going to talk a lot 关于 red-light therapies 和 near-infrared light therapies. 那些 are so called longer wavelengths. Longer wavelengths, just think of a bigger, longer wave, right, a bigger curve as opposed to short-wavelength light, which is going to be shorter, right? A short-wavelength light 会 be something like blue 或 green light 或 ultraviolet light.

安德鲁·休伯曼：

Blue, green 和 ultraviolet light, 因为 it's short-wavelength light, doesn't tend to penetrate 组织 非常 easily. It has to do 与 the way 那 the physics of light interacts 与 the physical properties of 你的 皮肤 和 other 组织 of 你的 身体. 但 basically, if 你 were to shine UV light onto 你的 arm, 对于 instance, it could impact the 皮肤 on the surface of the arm 和 maybe some of the cells just beneath the top layer of 皮肤, 但 it wouldn't penetrate much deeper.

安德鲁·休伯曼：

Long-wavelength light, like red light 和 near-infrared light, has 这 amazing ability to penetrate 通过 组织 including 你的 皮肤. 和 so if 我们 were to shine a red light 或 near-infrared light onto 你的 arm, it 会 pass 通过 那 top layer of 皮肤. It 可能 impact it a little bit, 但 it could penetrate deeper 进入 你的 皮肤, not just to the 皮肤 layers, 但 maybe even down to the bone, maybe even down to the bone marrow. 和 对于 many 人们, 这 会 be hard to conceptualize. 你 think, well, wait, I've got a 皮肤 there. Doesn't the light just bounce off? 和 the answer is no, 因为 of the way 那 long-wavelength light interacts 与 the absorbance properties of 你的 皮肤. Absorbance properties are just the way 那 the 皮肤 takes light 能量 和 converts it 进入 a 不同的 form of 能量. 和 你的 皮肤 is not able to take long-wavelength light like red light 和 near-infrared light 和 absorb it, 但 the 组织 deeper in 你的 身体 可以.

安德鲁·休伯曼：

So if 你 shine red light 或 near-infrared light onto the surface of 你的 皮肤, 你'll see a red glow there as a reflectance on the surface of 你的 皮肤. 但 a lot of the photon 能量, the light 能量 in 那些 longer wavelengths is indeed passing 通过 那些 top layers of 皮肤 进入 the deeper layers of 皮肤 和 可以 even make it 进入 the deep layers of 你的 arm.

安德鲁·休伯曼：

As 我们 start to transition 从 the physics of light to the biological impacts of light, just understanding 那 the 不同的 wavelengths of light impact 我们的 组织 at 不同的 水平, literally at 不同的 depths, 会 help 你 better understand how light of 不同的 colors, of 不同的 intensities, 和 how long 你 are exposed to 那些 colors 和 of light 可以 change the way 那 the cells 和 the organs of 你的 身体 work.

安德鲁·休伯曼：

If it didn't sound weird enough 那 你 可以 pass light 通过 particular 组织 和 have them land 和 be absorbed at 组织 deeper in 你的 身体, well, it turns out 那 不同的 wavelengths of light are also best absorbed by particular so-called organelles within 你的 cells. What are organelles? Organelles are the 不同的 compartments 和 不同的 functions within a given cell. So 对于 instance, 你的 mitochondria, which are responsible 对于 generating ATP 和 能量 in 你的 cells, 那些 exist at a particular depth, at a particular location within a cell. They're not all at the cell surface. They sit somewhat deeper in the cell. The nucleus of 你的 individual cells contains DNA 和 那 sits at a particular depth 或 location within 你的 cell.

安德鲁·休伯曼：

不同的 wavelengths of light not only 可以 penetrate down 进入 不同的 组织 和 进入 不同的 cells of 你的 身体, 但 they 可以 also penetrate 和 access particular organelles, meaning mitochondria 或 the nucleus 或 the 不同的 aspects of 你的 cells 那 are responsible 对于 不同的 functions. 这 is exquisitely 重要 和 it's exquisitely powerful 因为 as 你'll learn today, particular wavelengths of light 可以 be used to stimulate the function of particular organelles within particular cells, within particular organs of 你的 身体.

安德鲁·休伯曼：

I 可以 think of no other form of 能量, not sound, not chemical 能量, so not drugs, not food, not touch, no form of 能量 那 可以 target the particular locations in 我们的 cells, in 我们的 organelles, in 我们的 organs, 和 in 我们的 身体 to the extent 那 light 可以. In other words, if 你 had to imagine a real world surgical tool by which to modulate 我们的 biology light 会 be the sharpest 和 the most precise of 那些 tools. Now, let's talk 关于 how light is converted 进入 biological signals, several ways in which 那 is accomplished. 但 the fundamental thing to understand is 这 notion of absorption of light 能量, certain pigments 或 colors in the thing 那 is receiving the light 能量, meaning the thing 那 the light 能量 lands on are going to absorb particular wavelengths of light.

安德鲁·休伯曼：

Now, I promise 你 那 你 already intuitively know how 这 works. 对于 instance, if 你 were to sit outside on a 非常 bright sunny 天 和 你 had a table in front of 你 那 was metal, 你 可能 find it hard to look down at 那 metal table 因为 it's reflecting a lot of light of particular wavelengths. If 那 table were pitch black, 然而, it wouldn't reflect quite as much 和 你 会 be able to comfortably look at it. If 那 table were red, it 可能 be somewhere in between. If 那 table were green, it 会 be also somewhere in between. 但 let's say it were 非常 light blue, well then it 可能 reflect almost as much as a table 那 were just metal 或 a white table surface. So the absorbance properties of a given surface 会 determine whether 或 not light 能量 goes 和 stays at 那 location 和 has an impact on 那 location, 或 whether not it bounces off.

安德鲁·休伯曼：

Every biological function of light has to do 与 the absorbance 或 the reflectance of light 或 light passing 通过 那 particular thing, meaning 那 particular cell 或 compartment within a cell. I'd like to make it clear how 这 works by using the 三 primary examples of how 你 take light in 你的 environment 和 convert it 进入 biological events.

安德鲁·休伯曼：

我们 have photoreceptors in the back of 我们的 eyes. 这些 photoreceptors come in 二 major types, the so-called rods 和 the cones. The rods are 非常 elongated. They look like rods 和 the cones look like little triangles. Rods 和 cones have within them photopigment. They have dark stuff 那's stacked up in little layers. Rods absorb light of 本质上 any wavelength. There's some variation to 那, 但 let's just say rods don't care 关于 the 不同的 colors of light. They 会 absorb light 能量, photon 能量; if it's red, if it's green, if it's blue, if it's yellow, doesn't matter, as long as 那 light is bright enough. It turns out 那 rods are 非常, 非常 sensitive. They 可以 detect 非常, 非常 small numbers of photons. 和 rods are 本质上 what 你 use to see in 非常 low light conditions. 我们'll return 更多 to vision later.

安德鲁·休伯曼：

The cones come in 三 major varieties, at least 对于 most 人们 who aren't colorblind. 你 have so-called red cones, green cones 和 blue cones, 但 they're not 确实 red, green 和 blue in the back of 你的 eye. They are cones 那 either absorb long-wavelength light, red; 那 absorb medium-wavelength light, green; 或 short-wavelength light, blue. The reason 那 they 可以 absorb 不同的 wavelengths of light is they have 不同的 photopigments. So, much as the example I gave 之前, where 你 have 不同的 tables outside in the sunny environment 和 some are reflecting light 更多 than others, others are absorbing light 更多 than others, well, so too the photoreceptors, meaning the cones, are absorbing light of 不同的 wavelengths to 不同的 extents.

安德鲁·休伯曼：

In an absolutely incredible way, 你的 大脑 is actually able to take 那 information 和 create 这 perception 那 我们 have of color. 但 那's another story altogether 那 我们'll just touch on a little bit 更多 later. 但 if 你 want to learn all 关于, 你 可以 go to 我们的 episode on vision. So 那's photoreceptors in the back of 你的 eye absorbing light of 不同的 wave lengths, rods 和 cones.

安德鲁·休伯曼：

The other place, of course, where light 可以 impact 我们的 身体 is on 我们的 surface, on 我们的 皮肤. 和 皮肤 has pigment too. 我们 call 那 pigment melanin. 我们 have within 我们的 皮肤 multiple cell types, 但 in the top layer of 皮肤, which is called the epidermis, 我们 have keratinocytes 和 我们 have melanocytes. 和 the melanocytes are the cells 那 create pigmentation of the 皮肤. 和, of course, there is wide variation in the degree to which there's pigmentation of the 皮肤, which has to do 与 genetics, also has to do 与 where 你 were born 和 raised, how much light exposure 你 have throughout the year, right?

安德鲁·休伯曼：

So 人们 toward the equator tend to have 更多 melanocyte activity than 人们 who are located at the North Pole. 和 of course, 人们 live at 不同的 locations throughout the earth, regardless of their genetic background 或 where they were born. 和 so, as 你 all know, 与 light exposure, 那些 melanocytes 会 turn on genetic programs 和 other biological programs 那 lead to enhanced pigmentation on the 皮肤, which 我们 call tanning. The way they do 那 is by absorbing UV light specifically. So 与 melanocytes, 我们 have a 非常 具体的 example of how pigment absorbs light of a particular length, in 这 case, ultraviolet short-wavelength light, which in turn creates a set of biological signals within 那些 cells, 那 in turn creates changes in 我们的 皮肤 pigmentation.

安德鲁·休伯曼：

So 我们 have photoreceptors, 我们 have melanocytes. 和 the third example I'd like to provide is 那 of every cell of 你的 身体. 和 what I mean by 那 is 那 every cell of 你的 身体, meaning a cell 那 is part of 你的 bone 组织 或 你的 bone marrow 或 心脏 组织 或 liver 或 spleen, if light 可以 access 那些 cells, it 会 change the way 那 那些 cells function 对于 better 或 对于 worse. 对于 many organs within 我们的 身体 那 reside deep to 我们的 皮肤, light 从不 arrives at 那些 cells. A 确实 good example of 这 那 我们'll touch on later is the spleen. Unless 你 have massive damage to 你的 身体 surface, unless 你 literally have a hole in 你的 身体, light 会 从不 land directly on 你的 spleen. 但 the spleen still responds to light information 通过 indirect 通路, 和 那些 indirect 通路 arise 通过 light arriving on the 皮肤 和 light arriving on the eyes.

安德鲁·休伯曼：

So a key principle 那 I'm going to return to again 和 again today is 那 the ways in which light 可以 impact the biology of 你的 organelles, 你的 cells, 你的 organs, 和 the 组织 和, indeed, 你的 whole 身体, 可以 either be direct — so 对于 instance, light onto 你的 皮肤 impacting 皮肤 或 light onto 你的 photoreceptors impacting the photoreceptors of 你的 eye — 或 it 可以 be indirect; it 可以 be light arriving on 你的 photoreceptors, the photoreceptors then informing another cell type, which informs another cell type, which then relays a signal in kind of a bucket brigade manner off to the spleen 和 says to the spleen, "Hey, there's a lot of UV light out here. 我们're actually under 压力. In fact, there's so much UV light 那 你 need to activate an 免疫 program to protect the 皮肤." 和 in response to 那, the spleen 可以 deploy certain signals in certain cell types to go out 和 start repairing 皮肤 那's being damaged by UV light.

安德鲁·休伯曼：

So 我们 have direct signals 和 我们 have indirect signals, 但 in every case, it starts 与 light of particular wavelengths being absorbed by particular pigments 或 properties of the surfaces 那 那些 light waves land on. 和 as 你 recall 从 我们的 discussion 关于 the physics of light, remember, it's not just 关于 light impinging on the surface of 你的 身体. Light 可以 actually penetrate deep to the 皮肤 和 access at least certain 组织 和 cells of 你的 身体. Even though 你 可以't see 那些 wavelengths of light, they are getting 进入 你 all the time.

安德鲁·休伯曼：

So perhaps the best way to wrap 这 discussion 关于 the physics 和 the biology of light 与 a bit of a bow is to think 关于 light as a transducer, meaning a communicator of what's going on in the environment 大约 你, 和 那 some of 那些 signals are arriving at the surface 和 impacting the surface of 你的 身体, 但 many of 那些 signals are being taken by cells at the surface of 你的 身体, meaning 你的 melanocytes in 你的 皮肤 和 the photoreceptors of 你的 eyes, 和 then being passed off as a set of instructions to the other organs 和 组织 of 你的 身体.

安德鲁·休伯曼：

Light 可以 impact 我们的 biology in 非常 fast, moderately fast, 和 slow ways, 但 even the slow ways in which light 可以 impact 我们的 biology 可以 be 非常 powerful 和 非常 long-lasting. Just as a quick example of the rapid effects of light on 我们的 biology, if 你 were to go 从 a room 那 is dimly lit 或 dark 进入 a 非常 brightly lit room, 你 会 immediately feel 非常 alert. 你 可能 say, "No, 那's not true. Sometimes I wake up 和 it's dark, 和 I kind of stumble out 和 it's lighter out in the next room, 和 it takes me a while to wake up." Ah. 但 if 我们 were to move 你 从 a room 那 was 非常 dark to 非常 bright, a signal conveyed 从 你的 eyes to an area of 你的 大脑 stem called the locus coeruleus 会 cause the 释放 of 肾上腺素 相似的 to the 释放 of 肾上腺素 if 你 were to be dropped 进入 非常, 非常 寒冷 水 all of a sudden. It's just an immediate wake-up signal to 你的 大脑和身体.

安德鲁·休伯曼：

So 那's an example of a rapid effect of light on 你的 biology, not a 非常 typical 一, 但 nonetheless, 一 那 has a hardwired biological mechanism. At the other end of the spectrum are what 我们 call slow-integrating effects of light on 我们的 biology. So what I mean by 那 are ways in which 你的 身体 is taking information 关于 light in the environment, not in the sort of snapshot, acute sense, 但 averaging the amount of light in 你的 environment, 和 那 average light information is changing the way 那 你的 biology works. 但 even though 这 is a slow process, as I mentioned 之前, it's a 非常 powerful 一. The primary example of 这 are so-called circannual rhythms. Circannual rhythms are literally a calendar 那 exists within 你的 身体 那 uses not numbers, 但 amounts of 激素 那 are 释放了 进入 你的 大脑和身体 each 天 和 each 夜间 as a way of knowing where 你 are in the 365-天-calendar year.

安德鲁·休伯曼：

Now, 那 可能 seem kind of crazy, 但 it's not crazy. The earth travels 大约 the sun once every 365 天, 和 depending on where 你 are on the earth, where 你 live, 你 are going to get 更多 或 更少 light each 天, on average, depending on the time of year. So if 你're in the Northern Hemisphere in the winter months, 天 are shorter, nights are longer. In the summer months, 天 are longer, nights are shorter. 和 of course, things change whether 或 not 你're in the Northern Hemisphere 或 the Southern Hemisphere. 但 nonetheless, in short 天, 你 have 更多 darkness, 那's obvious.

安德鲁·休伯曼：

和 if 你 understand 那 light arriving on the eyes is absorbed by a particular cell type called the intrinsically photosensitive ganglion cell. It's just a name. 你 don't need to know the name, 但 if 你 want, it's the so-called intrinsically photosensitive ganglion cell, also called the melanopsin cell, 因为 it contains an opsin, a photopigment 那 absorbs short-wavelength light 那 arrives 通过 sunlight. 那些 cells communicate to particular stations in the 大脑 那 in turn connect to 你的 so-called pineal gland, which is 这 little pea -sized gland in the middle of 你的 大脑 那 releases a 激素 called melatonin. The only thing 你 need to know is 那 light activates 这些 particular cells, the intrinsically photosensitive melanopsin cells, which in turn shuts down the production of melatonin 从 the pineal gland.

安德鲁·休伯曼：

If 你 think 关于 这 in terms of the travel of the earth 大约 the sun across the year, what it means is 那 in short 天, 因为 there's 非常 little light, on average, landing on 这些 cells, the duration of melatonin 释放 会 be much longer, 因为, as I mentioned 之前, light inhibits, it shuts down melatonin. Whereas in the summer months, much 更多 light, on average, 会 land on 你的 eyes, 因为 天 are longer, even if 你're spending 更多 time indoors, on average, 你're going to get 更多 light to activate 这些 cells. 和 因为 light shuts down melatonin production, what 你'll find is 那 the duration of melatonin 释放 对于 the pineal is much shorter.

安德鲁·休伯曼：

So melatonin is a transducer. It's a communicator of how much light, on average, is in 你的 physical environment. What 这 means is 对于 人们 living in the Northern Hemisphere, 你're getting 更多 melatonin 释放 in the winter months than 你 are in the summer months. So 你 have a calendar 系统 那 is based on a 激素, 和 那 激素 is using light in order to determine where 你 are in 那 journey 大约 the sun.

安德鲁·休伯曼：

Now, 这 is beautiful, at least to me it's beautiful, 因为 what it means is 那 the environment 大约 us is converted 进入 a signal 那 changes the environment within us. 那 signal is melatonin, 和 melatonin is well-known 对于 its role in making us sleepy each 夜间 和 allowing us to fall asleep.

安德鲁·休伯曼：

Many of 你 have probably heard 之前, I am not a big fan of melatonin supplementation 对于 a number of reasons, 但 just as a quick aside, the 水平 of melatonin 那 are in most supplements are far too high to 确实 be considered physiological. They are indeed supraphysiological, in most cases, 和 melatonin 可以 have a number of 不同的 effects, not just related to sleep, 但 那's supplemented melatonin.

安德鲁·休伯曼：

Here I'm talking 关于 我们的 natural production 和 释放 of melatonin according to where 我们 are in the 365-天-calendar year. Endogenous melatonin, meaning the melatonin 那 我们 make within 我们的 bodies naturally, not melatonin 那's supplemented, has 二 general categories of effects. The 首先 set of effects are so-called regulatory effects, 和 the others are protective effects. The regulatory effects are, 对于 instance, 那 melatonin 可以 positively impact bone mass. So melatonin 可以, 对于 instance, turn on the production of osteoblasts, which are 本质上 stem cells 那 make 更多 bone 对于 us, 那 make 我们的 bone stronger, 和 那 可以 replace damaged aspects of 我们的 bone.

安德鲁·休伯曼：

Melatonin is also involved in maturation of the gonads 期间 puberty, the ovaries 和 the testes. 尽管 there the effects of melatonin tend to be suppressive on maturation of the ovaries 和 testes, meaning high 水平 of melatonin tend to 减少 testicle volume 和 减少 certain functions within the testes, including sperm production 和 testosterone production. 和 within the ovaries, melatonin 可以 suppress the maturation of eggs, et cetera.

安德鲁·休伯曼：

Now, I don't want anyone to get scared if 你've been taking melatonin, mostly effects of melatonin on 那些 functions are reversible. 但 I 应该 point out 那 一 of the reasons why children don't go 进入 puberty until a particular age is 那 young children tend to have chronically high endogenous melatonin, 和 那 is healthy, to keep them out of puberty until it's the right time 对于 puberty to happen. So melatonin 可以 增加 bone mass, 但 减少 gonad mass, so to speak.

安德鲁·休伯曼：

It's going to have varying effects depending on the ratios 和 水平 of other 激素 和 other biological events in the 身体. 但 as 你 可以 see, melatonin has 这些 powerful regulatory effects on other 组织. I 应该 also mention 那 melatonin is a powerful modulator of placental development. So 对于 anyone 那's pregnant, if 你're considering melatonin supplementation, please, please, please talk to 你的 ob-gyn; talk to 你的 other doctors as well. 你 want to be 非常, 非常 cautious 因为 of the powerful effects 那 melatonin 可以 have on the developing fetus 和 placenta.

安德鲁·休伯曼：

对于 人们 那 are not pregnant, in fact, all 人们, melatonin has a powerful effect on the central 神经系统 as a whole. 你的 大脑 和 spinal cord are the major components of 你的 central 神经系统, 和 melatonin, 因为 it's associated 与 darkness — which is just another way of saying 那 light suppresses melatonin; melatonin is thereby associated 与 the dark phase of each 24-小时 cycle — it 可以 have a number of 不同的 effects in terms of waking up 或 making 我们的 身体 feel 更多 sleepy. 和 it does 那 by way of impacting cells within 我们的 神经系统, literally turning on certain 大脑 areas, turning off other 大脑 areas, 和 it does 那 通过 a whole cascade of biological mechanisms. A bit too detailed to get 进入 today.

安德鲁·休伯曼：

So melatonin is regulating how awake 或 asleep 我们 are. It tends to make us 更多 asleep, incidentally. It's regulating 我们的 timing of puberty, 和 it's regulating how 我们的 gonads, the testes 和 ovaries, function, even in adulthood to some extent. 和 it's regulating bone mass.

安德鲁·休伯曼：

As I mentioned 之前, melatonin also has protective effects. It 可以 activate 我们的 免疫系统. It is among the most potent antioxidants, so it is known to have certain anticancer properties 和 things of 那 sort, which is not to say 那 你 simply want 更多 melatonin. I think a lot of 人们 get misled when they hear something like melatonin has anticancer properties. 那 doesn't mean 那 just cranking up the 水平 of melatonin by supplementing it, 或 by spending time in darkness 和 not getting any light, which 会 of course inhibit melatonin, is going to be beneficial 对于 combating cancer. 那's not the way it works. It is actually the rise 和 fall of melatonin every 24-小时 cycle 和 the changes in the duration of 那 melatonin signal throughout the season 那 has 这些 anticancer 和 antioxidant effects. So when 我们 think 关于 light impacting 我们的 biology, the reason I bring up melatonin as the primary example of 那 is A, 因为 melatonin impacts so many 重要 functions within 我们的 大脑和身体, 但 also 因为 激素 in general, not 总是, 但 in general, are responsible 对于 这些 slow modulatory effects on 我们的 biology.

安德鲁·休伯曼：

So I'm using 这 as an example of how light throughout the year is changing the way 那 the 不同的 cells 和 组织 和 organs of 你的 身体 are working, 和 那 melatonin is the transducer of 那 signal. So at 这 point, 我们 可以 say light powerfully modulates melatonin, meaning it shuts down melatonin. Melatonin is both beneficial 对于 certain 组织 和 suppressive 对于 other 组织 和 functions. What 应该 我们 do 与 这 information? Well, it's 非常 well-established now 那 一 of the best things 那 我们 可以 all do is to get the proper amount of sunlight each 天. 和 by proper, I mean appropriate 对于 那 time of year.

安德鲁·休伯曼：

So in the summer months where the 天 are longer 和 nights are shorter, 我们 会 all do well to get 更多 sunlight in 我们的 eyes. 和 again, it's going to be to 我们的 eyes, 因为 as 你 recall, the pineal sits deep in the 大脑, 和 light 可以't access the pineal directly, at least not in humans. So in order to get light information to the pineal 和 thereby get the proper 水平 of melatonin according to the time of year, 我们 应该 all try 和 get outside as much as 可能 期间 the long 天 of summer 和 spring. 和 in the winter months, it makes sense to spend 更多 time indoors.

安德鲁·休伯曼：

对于 那些 of 你 那 suffer 从 seasonal effective disorder, which is a seasonal depression, 或 feel low 期间 the fall 和 winter months, there are ways to offset 这. 我们 did an entire episode on 情绪 和 circadian rhythms where 我们 describe 这. So it does make sense 对于 some 人们 to get 更多 bright light in their eyes early in the 早晨 和 throughout the 天 期间 the winter months as well. 但 nonetheless, changes in melatonin, meaning changes in the duration of melatonin 释放 across the year, are normal 和 healthy. So provided 那 你're not suffering 从 depression, it's going to be healthy to somewhat modulate 你的 amount of indoor 和 outdoor time across...

安德鲁·休伯曼：

Healthy to somewhat modulate 你的 amount of indoor 和 outdoor time across the year. The other thing to understand is 这 非常 firmly established fact, which is light powerfully inhibits melatonin. If 你 wake up in the middle of the 夜间, 和 你 go 进入 the bathroom 和 你 flip on the lights, 和 那些 are 非常 bright overhead fluorescent lights, 你的 melatonin 水平 — which 会 ordinarily be quite high in the middle of the 夜间 因为 你've been eyes-closed in the dark, presumably — 会 immediately plummet to near zero 或 zero. 我们 会 all do well regardless of time of year to not destroy 我们的 melatonin in the middle of the 夜间 in 这 way. So if 你 need to get up in the middle of the 夜间 和 use the restroom, which is a perfectly normal behavior 对于 many 人们, use the minimum amount of light required in order to safely move 通过 the environment 那 你 need to move 通过.

安德鲁·休伯曼：

Melatonin needs to come on early in the 夜间. It actually starts rising in the 晚上 和 towards sleep. 但 then as 你 close 你的 eyes 和 你 go to sleep, melatonin 水平 are going to continue to rise at least 对于 several 小时 进入 the 夜间. Again, if 你 get up in the middle of the 夜间, 确实 try hard not to flip on a lot of bright lights. If 你 do 那 every once in a while, it's not going to be a problem. 但 if 你're doing 那 夜间 之后 夜间, 你 are 确实 disrupting 这 fundamental signal 那 occurs every 夜间 regardless of winter, spring, summer, et cetera. 和 那 is communicating information 关于 where 你的 大脑和身体 应该 be in time. 和 I know 那's a little bit of a tricky concept, 但 确实 我们的 身体 is not meant to function in the same way 期间 the winter months as the summer months.

安德鲁·休伯曼：

There are functions 那 are specifically optimal 对于 the shorter 天 of winter, 和 there are functions 那 are specifically optimal 对于 the longer 天 of summer. So again, try to avoid bright light exposure to 你的 eyes in the middle of the 夜间. 和 对于 那些 of 你 那 are doing shift work, what I 可以 say is try 和 avoid getting bright light in 你的 eyes in the middle of 你的 sleep cycle. So even if 你're sleeping in the middle of the 天 因为 你 have to work at 夜间, if 你 wake up 期间 那 bout of sleep, 确实 try hard to limit the amount of light, which is going to be harder 对于 shift workers, right? 因为 there are generally a lot 更多 lights on 和 bright lights outside too. 你 会 want to close the blinds 和 limit artificial light inside. 一 way to bypass some of the inhibitory effects of light on melatonin is to change 你的 physical environment by, 对于 instance, dimming the lights. 那's 一 simple way, 非常 low-cost way. In fact, 你'll save money by dimming the lights 或 turning them off.

安德鲁·休伯曼：

The other is if 你 are going to use light, using long-wavelength light 因为, as 你 recall, 这些 intrinsically photosensitive melanopsin cells within 你的 retina 那 convey the signal 关于 bright light in 你的 environment to impact melatonin, to shut down melatonin, respond to short wavelengths of light. So red light is long-wavelength light. 你 now understand 那 从 我们的 discussion 关于 the physics of light. 和 if 你 were to use amber-colored light 或 red light 和, even better, dim amber 或 dim red light in the middle of the 夜间, well, then 你 会 probably not 减少 melatonin at all unless 那些 red lights 和 amber lights are 非常, 非常 bright. Any light, provided it's bright enough, 会 shut down melatonin production. 一 final point 关于 melatonin, 和 这 relates to melatonin supplementation as well, is 那 now 那 你 understand how potently melatonin 可以 impact things like cardiovascular function, 免疫 function, anticancer properties, bone mass, gonad function, et cetera 你 可以 understand why it 会 make sense to be cautious 关于 melatonin supplementation, 因为 supplementation tends to be pretty static.

安德鲁·休伯曼：

It's X number of milligrams per 夜间, whereas normally endogenously the amount of melatonin 那 你're releasing each 夜间 is changing according to time of year, 或 if 你 happen to live in an area where there isn't much change in 天 length across the year. So 对于 instance, if 你 live near the equator, well then 你的 身体 is accustomed to having regular amounts of melatonin each 夜间. When 你 start supplementing melatonin, 你 start changing the total amount of melatonin, obviously, 但 你're also changing the normal rhythms in how much melatonin is being 释放了 进入 你的 大脑和身体 across the 365-天-calendar year. So while I'm somebody who readily embraces supplementation in various forms 对于 things like sleep 和 专注, et cetera, when it comes to melatonin, I'm extremely cautious. 和 I think it's also 一 of the few examples where a 激素 is available 没有 prescription. Over the counter, 你 可以 just go 进入 a pharmacy 或 drugstore, order online 这 激素, which is known to have all 这些 powerful effects. So I get 非常, 非常 concerned when I hear 关于 人们 taking melatonin, 尤其是 at the 水平 那 are present in most supplements.

安德鲁·休伯曼：

It's been recognized 对于 a 非常 long time, 和, in fact, there are now 数据 to support the fact 那 animals of all kinds, including humans, 会 seek out mates 和 engage in mating behavior 更多 frequently 期间 the long 天 of spring 和 summer. 那's right. In seasonally breeding animals, of course 这 is the case, 但 in humans as well, there is 更多 seeking out of mates 和 mating behavior in longer-天 times of year.

安德鲁·休伯曼：

Now, 你 could imagine at least 二 mechanisms by which 这 occurs. The 首先 mechanism 我们 could easily map to melatonin, 和 the fact 那 melatonin is suppressive to various aspects of the so-called gonadal axis, which is basically a fancy way of saying 那 melatonin inhibits testosterone 和 estrogen output 从 the testes 和 从 the ovaries. I just want to remind 人们 那 both males 和 females make testosterone 和 estrogen, 尽管 in 不同的 ratios, 通常, in males versus females, 和 那 both testosterone 和 estrogen are critical 对于 the desire to mate 和 对于 mating behavior. There's a broad misconception 那 testosterone is involved in mating behavior, 和 estrogen's involved in other behaviors, 但 having enough estrogen is critical 对于 both males 和 females in order to maintain the desire to mate 和, indeed, the ability to mate.

安德鲁·休伯曼：

I discuss 这 on the episode on optimizing testosterone 和 estrogen. So if 你'd like 更多 details on 那, please see 那 episode of the Huberman Lab 播客. Okay, so if melatonin is suppressive to the so-called gonadal axis 和 减少 overall 水平 of testosterone 和 estrogen in males 和 females 和 light inhibits melatonin, then when there's 更多 light, then there's 更少 melatonin 和 更多 激素 output 从 the gonads. 和 indeed, 那's how the 系统 works, 但 那's not the entire story. It turns out 那 there is a 秒 so-called parallel 通路, meaning a 不同的 biological 通路 那 operates in parallel to the light suppression of melatonin 通路 那 provides a basis 对于 longer 天, inspiring 更多 desire to mate 和 更多 mating behavior. So if 我们 think of the 首先 通路 involving melatonin as sort of a brake on 这些 reproductive 激素, the 秒 mechanism is 更多 like an accelerator on 那些 激素, 和 yet it still involves light.

安德鲁·休伯曼：

As I'm 关于 to tell 你, in animals such as mice, 但 also in humans, exposure to light, in particular UV blue light, so short wavelengths of light, 可以 trigger 增加 in testosterone 和 estrogen 和 the desire to mate. Now, what's 尤其是 重要 关于 这 accelerator on the desire to mate 和 mating behavior 和 激素 is 那 it is driven by exposure to light, 但 it is not the exposure of light to the eyes. It turns out 那 it is the exposure of 你的 皮肤 to particular wavelengths of light 那 is triggering 增加 in the 激素 testosterone 和 estrogen, leading to 增加了 desire to mate. As it turns out, 你的 皮肤, which most of us just think of as a way to protect the organs of 我们的 身体 — 或 something to hang clothes on 或 ornaments on if 你're somebody who has earrings 和 so forth — 你的 皮肤 is actually an endocrine organ, meaning it is a 激素-producing 和 激素-influencing organ. I promise what I'm 关于 to tell 你 next 会 forever change the way 那 你 think 关于 你的 皮肤 和 light 和 the desire to mate 和, indeed, even mating behavior.

安德鲁·休伯曼：

I think the 结果 are best understood by simply going 通过 the primary 数据, meaning the actual 研究 on 这 topic. 和 to do so, I'm going to review a recent paper 那 was published in the journal Cell Reports, Cell Press journal, excellent journal. 这 is a paper 那 came out in 2021, entitled "皮肤 exposure to UVB light induces a 皮肤-大脑-gonad axis 和 sexual behavior." 和 I want to emphasize 那 这 was a paper 那 focused on mice in order to address 具体的 mechanisms, 因为 in mice 你 可以 so-called knock out particular genes. 你 可以 remove particular genes to understand mechanism. 你 just 可以't do 那 in humans in any kind of controlled way, at least not at 这 point in time. 和 这 研究 also explores humans 和 looked at human 受试者, both men 和 women.

安德鲁·休伯曼：

The basic finding of 这 研究 was 那 when mice 或 humans were exposed to UVB, meaning ultraviolet blue light, so short-wavelength light of the sort 那 comes 通过 in sunshine 但 is also available 通过 various artificial sources, if they received enough exposure of 那 light to their 皮肤, there were 增加 in testosterone 那 were observed within a 非常 brief period of time, also 增加 in the 激素 estrogen. 和 I 应该 point out 那 the proper ratios of estrogen 和 testosterone were maintained in both males 和 females, at least as far as 这些 数据 indicate. 和 mice tended to seek out mating 更多 和 mate 更多.

安德鲁·休伯曼：

There were also 增加 in gonadal weight, literally 增加 in testes size 和 in ovarian size, when mice were exposed to 这 UVB light past a certain threshold. Now, as I mentioned 之前, the 研究 also looked at humans. They did not look at testes size 或 ovarian size in the human 受试者. 然而, 因为 they are humans, they did address the psychology of 这些 human beings 和 address whether 或 not they had 增加 in, 对于 instance, aggressiveness 或 in passionate feelings 和 how their perception of other 人们 changed when they were getting a lot of UVB light exposure to the 皮肤. So 之前 I get 进入 some of the 更多 重要 details of the 研究 和 how it was done 和 how 你 可以 leverage 这 information 对于 yourself if 你 desire, I just want to highlight some of the basic findings overall.

安德鲁·休伯曼：

UVB exposure 增加了 这些 so-called sex steroid 水平 in mice 和 humans. The sex steroid 激素; when 我们 say steroids, 我们 don't mean anabolic steroids taken exogenously. I think when 人们 hear the word steroids, they 总是 think steroid abuse 或 use, rather steroid 激素 such as testosterone 和 estrogen went up when mice 或 humans had a lot of UVB exposure to their 皮肤. 秒 of all, UVB light exposure to the 皮肤 enhanced female attractiveness, so the perceived attractiveness of females by males, 和 增加了 the receptiveness 或 the desire to mate in both sexes. UVB light exposure also changed various aspects of female biology related to fertility, in particular, follicle growth. Follicle 和 egg maturation are well-known indices of fertility 和 of course correlate 与 the menstrual cycle in adult humans 和 is related overall to the propensity to become pregnant. UVB light exposure enhanced maturation of the follicle, which just meant 那 更多 healthy eggs were being produced.

安德鲁·休伯曼：

这些 are impressive effects. 首先 of all, they looked at a large number of variables in the 研究, 和 the fact 那 they looked at mice 和 humans is terrific. I think 那 oftentimes 我们 find it hard to translate 数据 从 mice to humans. So the fact 那 they looked at both in parallel is wonderful. In the mice 和 in the humans, they established a 方案 那 本质上 involved exposing the 皮肤 to UV light 那 was equivalent to 关于 20 to 30 分钟 of midday sun exposure. Now of course, where 你 live in the world 会 dictate whether 或 not 那 midday sun is 非常, 非常 bright 和 intense 或 is 更少 bright. Maybe there's cloud cover, et cetera. 但 since imagining 那 most 人们 are interested in ways to 增加 testosterone 和/或 estrogen in humans 和 are not so much interested in increasing testosterone in mice, I'm going to just review what they did in the human population, 或 the human 受试者.

安德鲁·休伯曼：

What they did is they had 人们, 首先 of all, establish a baseline, 和 the way they establish a baseline was a little bit unusual 但 会 make perfect sense to 你. They had 人们 wear long sleeves 和 本质上 cover up 和 avoid sunlight 对于 a few 天 so they could measure their baseline 激素 in the absence of getting a lot of UVB light exposure 从 the sun 或 从 other sources. Now of course, 这些 人们 had access to artificial lights, 但 as I've pointed out on 这 podcast 之前, it's pretty unusual 那 你'll get enough UVB exposure 从 artificial lights throughout the 天 和 in the 早晨. 你 need a lot of UVB exposure, 或 我们 应该 be getting a lot of UVB exposure to 我们的 eyes 和 to 我们的 face 和 to 我们的 皮肤 throughout the 天, provided 我们're not getting sunburnt. 这 is actually a healthy thing 对于 情绪 和 对于 能量 throughout the 天.

安德鲁·休伯曼：

It's only at 夜间, basically between the 小时 of 关于 10:00 p.m. 和 4:00 a.m., 那 even a tiny bit of UVB exposure 从 artificial sources 可以 mess us up in terms of 我们的 sleep 和 我们的 能量 水平 和 so on. 和 那's 因为 of the potent effect of UVB on suppressing melatonin. So the point here is 那 they establish a baseline whereby 人们 were getting some artificial light exposure throughout the 天, 但 they weren't getting outside a lot. They weren't getting a lot of sunlight. 和 then they had 人们 receive a dose of UVB light exposure 那 was 关于 20 to 30 分钟 outdoors. They had 人们 wear short sleeves — no hat, no sunglasses. Some 人们 wore sleeveless shirts. They encourage 人们 to wear shorts, so they were indeed wearing clothing. They were not naked, 和 they were wearing clothing 那 was culturally 和 situationally appropriate, at least 对于 the part of the world where 这 研究 was done.

安德鲁·休伯曼：

和 they had 人们 do 那 二 或 三 times a 周. So in terms of a 方案 那 你 可能 export 从 这 研究, basically getting outside 对于 关于 30 分钟 二 或 三 times a 周 in a minimum of clothing, 和 yet still wearing enough clothing 那 is culturally appropriate. They were outside. They weren't sunbathing, flipping over on their back 和 front. They were just moving 关于 doing things. They could read. They could talk. They could go 关于 other activities, 但 they weren't wearing a broad brim hat 或 a hat of any kind. They're just getting a lot of sun exposure to their 皮肤. They did 这 对于 a total of 10 to 12 UVB treatments. So 这 took several 周, right? It took 关于 a month if 你 think 关于 it, 二 或 三 times per 周 对于 a total of 10 to 12 UVB treatments.

安德鲁·休伯曼：

这些 treatments, of course, are just being outside in the sun. 和 then they measured 激素, 和 they measured the psychology of 这些 male 和 female adult 受试者. Let's 首先 look at the psychological changes 那 这些 human 受试者 experienced 之后 getting 10 to 12 of 这些 UVB light exposure, outdoor in sunlight type treatments. They did 这 by collecting 血液 samples throughout the 研究, 和 they saw significant 增加 in the 激素 beta estradiol, which is 一 of the major forms of estrogen; progesterone, another 重要 steroid 激素; 和 testosterone, in both men 和 women. Now, an 重要 point is 那 the testosterone 增加 were significantly higher in men 那 happened to originate 从 countries 那 had low UV exposure, compared to 个体 从 countries 与 high UV exposure. Now, 这 ought to make sense if 我们 understand a little bit 关于 how the 皮肤 functions as an endocrine organ.

安德鲁·休伯曼：

Many of 你 have probably heard of vitamin D3, which is a vitamin 那 我们 all make. Many 人们 supplement it, as well, if they need additional vitamin D3. 我们 all require sunlight in order to allow vitamin D3 to be synthesized 和 perform its roles in the 身体. 和 it turns out 那 人们 who have darker 皮肤 actually need 更多 vitamin D3 和/或 更多 sunlight exposure in order to activate 那 D3 通路 than do 人们 与 pale 皮肤. 和 这 应该 make sense to all of 你 given what 你 now understand 关于 melanocytes, 那 cell type 那 我们 discussed earlier, 因为 melanocytes have pigment within them. 和 if 你 have darker 皮肤, it means 那 你 have 更多 melanocytes 或 那 你 have melanocytes 那 are 更多 efficient at creating pigment. 和 as a consequence, the light 那 lands on 你的 皮肤 会 be absorbed by 那些 melanocytes, 和 更少 of it is able to impact the D3 通路.

安德鲁·休伯曼：

Whereas if 你 have pale 皮肤, 更多 of the light 那 lands on 你的 皮肤 可以 trigger the synthesis 和 assist the actions of vitamin D3. Similarly, in 这 研究, they found 那 人们 who had paler 皮肤 和/或 who originated 从 countries where they had 更少 UVB light exposure across the year had greater, meaning 更多 significant 增加 in testosterone overall than did 人们 who already were getting a lot of UVB exposure. 这 led them to explore so-called seasonal changes in testosterone 那 occurred normally in the absence of any light exposure treatment. So up until now, I've been talking 关于 the aspects of 这 研究 involving 人们 getting outside 对于 关于 20 to 30 分钟 per 天 in sunlight in a minimum of clothing. There was an 增加 in testosterone observed in both men 和 women. The 增加 in testosterone were greater 对于 人们 那 had paler 皮肤 than darker 皮肤.

安德鲁·休伯曼：

So the 数据 I'm 关于 to describe also come 从 这 same paper, 但 do not involve 20-to-30-分钟 daily sun exposure 方案. It's simply addressing whether 或 not testosterone 水平 change as a function of time of year. They measure testosterone across the 12-month calendar. 这 研究 was done on 受试者 living in the Northern Hemisphere 对于 the entire year. 和 so in the months of January, February, 和 March, of course, the length of 天 is shortest 和 the length of nights is longest. 和, of course, in the spring 和 summer months, June, July, August, September, 和 so on, the 天 are much longer 和 the nights are shorter. 和 what they observed was 非常 obvious. They observed 那 testosterone 水平 were lowest in the winter months 和 were highest in the months of June, July, August 和 September. Now 这些 are 非常 重要 数据.

安德鲁·休伯曼：

At least to my knowledge, 这些 are the 首先 数据 systematically exploring the 水平 of sex steroid 激素 in humans as a function of time of year, 和 thereby as a function of how much sunlight exposure they're getting. 和 what's remarkable 关于 这些 数据 is 那 they map 非常 well to the 数据 in mice 和 the other 数据 in 这 paper on humans, which illustrate 那 if 你're getting 更多 UVB exposure, 你的 testosterone 水平 are higher. 这 研究 went a step further 和 explored whether 或 not the amount of sunlight exposure 那 一 is getting to their 皮肤 influences their psychology in terms of whether 或 not they have 增加了 desire to mate 和 so on. It's well known 那 sunlight exposure to the eyes 可以 增加 情绪. 和 I talked 关于 这 in the podcast episode 与 my guest Dr. Samer Hattar, who's the Director of the Chronobiology Unit at the National Institutes of 心理健康.

安德鲁·休伯曼：

和 Samer's recommendation is 那 人们 get as much bright light exposure as they safely 可以 in the 早晨 和 throughout the 天, 对于 sake of both sleep 和 能量, 但 also 对于 增强 情绪 和 regulating appetite. In 这 研究, it was found 那 both males 和 females had higher 水平 of romantic passion 之后 getting the UV treatment. In fact, some of them reported 增加 in romantic passion 从 just 一 或 二 of 这些 UV treatments, so they didn't have to go 通过 all 10 或 12 in order to get a statistically significant 增加 in passion. Now, when 我们 talk 关于 passion, as the authors of 这 paper acknowledge, there's 确实 二 forms. There is emotional 和 sexual, 和 they parse 这 pretty finely. I don't want to go 进入 all the details, 和 我们 可以 provide a reference 和 link to 这 研究 if 你'd like to look at 那些 details.

安德鲁·休伯曼：

但 what they found was 那 women receiving 这 UVB light exposure focused 更多 on 增加 in physical arousal 和 sexual passion, whereas the men actually scored higher on the cognitive dimensions of passion, such as obsessive thoughts 关于 their partner 和 so on. Regardless, both males 和 females experienced 和 reported an 增加 in sexual passion 和 desire to mate. 和 我们 now know there were 增加 in testosterone 和 estrogen, which, of course, could be driving the psychological changes, 尽管 I'm sure 那 那些 interact in both directions, meaning the 激素 no doubt affect psychology. 和 no doubt the psychology, 这些 changes in passionate feelings, no doubt also 增加了 或 changed the 激素 水平 as well. 和 I want to reemphasize 那 there was a component of the 研究 那 had no deliberate daylight sunlight exposure 对于 20 或 30 分钟, 但 rather just looked at 激素 水平 throughout the year 和 found 那 the 增加 in 天 length correlated 与 增加 in testosterone 和 sexual passion.

安德鲁·休伯曼：

Now, my opinion, 这 is a 非常 noteworthy 研究 因为 it 确实 illustrates 那 sunlight 和 daylight 可以 impact the melatonin 通路 和 thereby take the foot off the brake, so to speak, on testosterone, estrogen, 和 the desire to mate. It also emphasizes 那 sunlight, UVB light, 可以 directly trigger 激素 通路 和 desire to mate 和 mating behavior. Now, 这 研究 went a step further in defining the precise mechanism by which light 可以 impact all 这些 激素 和 这 desire to mate. 和 here, understanding the mechanism is key if 你 want to export a particular 方案 或 tool 那 你 可能 apply. 我们 talked earlier 关于 how UVB light exposure to the eyes triggers activation of 这些 particular neurons within the eye 和 then 与 centers deeper in the 大脑, 和 eventually the pineal gland, to suppress the output of melatonin 和, thereby to allow testosterone 和 estrogen to exist at higher 水平, 因为 melatonin 可以 inhibit testosterone 和 estrogen.

安德鲁·休伯曼：

In 这 研究, they were able to 非常 clearly establish 那 it is sunlight exposure to 我们的 皮肤 那 is causing 这些 激素 增加 那 they observed in mice 和 humans. 和 the way they did 那 was to use the so-called knockout technology, the ability to remove 具体的 genes within 具体的 组织 of the 身体. 和 what they found is 那 UVB light, meaning sunlight-exposed 皮肤, upregulated, meaning 增加了 the activity of something called p53, which is involved in the maturation of cells 和 various aspects of cellular function. 和 the cells they were focused on were the keratinocytes, which 你 are now familiar 与 从 我们的 earlier discussion 关于 the fact 那 the epidermis of 你的 皮肤 contains mainly keratinocytes 和 melanocytes. Sunlight exposure 增加了 p53 activity in the 皮肤, 和 p53 activity was required 对于 the downstream 增加 in ovarian size, in testicular size, in testosterone 增加, in the estrogen 增加, 和 the various other changes 那 they observed at the physiological 水平 when animals 或 humans were exposed to sunlight.

安德鲁·休伯曼：

So 这些 数据 are 重要 因为 what they mean is 那 not only is it 重要 那 我们 get sunlight exposure early in the 天 和 throughout the 天 to 我们的 eyes, at least as much as is safely 可能, 但 那 我们 also need to get UVB sunlight exposure onto 我们的 皮肤 if 我们 want to activate 这 p53 通路 in keratinocytes 和 the testosterone 和 estrogen 增加 那 are downstream of 那 p53 通路. So even though the gene knockout 研究 were done on mice, they clearly show 那 if 你 remove p53 从 the 皮肤, 那 这些 effects simply do not occur. So in terms of thinking 关于 a 方案 to 增加 testosterone 和 estrogen, 情绪 和 feelings of passion, the idea is 那 你 会 want to get 这些 二 to 三 exposures per 周 minimum of 20 to 30 分钟 of sunlight exposure onto as much of 你的 身体 as 你 可以 reasonably expose it to.

安德鲁·休伯曼：

和 when I say reasonably, I mean of course 你 have to obey cultural constraints, decency constraints, 和 of course 你 have to also obey the fact 那 sunlight 可以 burn 你的 皮肤. So many 人们 are probably going to ask, "What happens if 你 wear sunscreen?" In theory, 因为 sunscreen has UV protection, it 会 block some of 这些 effects. Now, I'm not suggesting 那 人们 do away 与 sunscreen entirely. I do hope to do an episode all 关于 sunscreen in the future, 因为 sunscreen is a bit of a controversial topic. 皮肤 cancers are a real thing, 和 many 人们 are 尤其是 prone to 皮肤 cancer, so 你 need to take 那 seriously. Some 人们 are not 非常 prone to 皮肤 cancers 和 可以 tolerate much 更多 sun exposure. 你're probably familiar 与 the simple fact 那 if 你've gone outside on the beach 与 friends, some 人们 get burned 非常 easily, others don't.

安德鲁·休伯曼：

So 你 确实 应该 prioritize the health 和 the avoidance of sunburn on 你的 皮肤. 然而, 这些 数据 和 other 数据 point to the fact 那 我们 应该 all probably be striving to get 更多 sunlight exposure onto 我们的 皮肤 期间 the winter months 和 still getting sunlight exposure onto 我们的 皮肤 in the summer months, provided 我们 可以 do 那 没有 damaging 我们的 皮肤. Another set of 非常 impressive effects of UVB light, whether 或 not it comes 从 sunlight 或 从 an artificial source, is the effect of UVB light on 我们的 tolerance 对于 pain. It turns out 那 我们的 tolerance 对于 pain varies across the year 和 那 我们的 pain tolerance is 增加了 in longer 天 conditions. 和 as 我们 saw 与 the effects of UVB on 激素 和 mating, again, 这 is occurring via UVB exposure to the 皮肤 和 UVB exposure to the eyes. I want to just describe 二 研究 那 确实 capture the essence of 这些 结果.

安德鲁·休伯曼：

I'm going to discuss 这些 in kind of a top contour fashion. I won't go 进入 it as quite as much depth as I did the last 研究, 但 I 会 provide links to 这些 研究 as well. The 首先 研究 is entitled "皮肤 exposure to ultraviolet B rapidly activates systemic neuroendocrine 和 immunosuppressive responses." 和 你 可能 hear 那 和 think, "Oh, immunosuppressive, 那's bad." 但 basically what they observed is 那 even 一 exposure to UVB light changed the output of particular 激素 和 神经化学物质 in the 身体, such as corticotropin 激素 和 beta-endorphins, which are 这些 endogenous opioids. 我们've all heard of the opioid crisis, which is 人们 getting addicted to opioids 那 they are taking in drug form, pharmaceuticals. 但 here I'm referring to endorphins 那 我们的 身体 naturally manufactures 和 releases in order to counter pain 和 act as somewhat of a psychological soother also.

安德鲁·休伯曼：

因为 of course, physical pain 和 emotional pain are intimately linked in the 大脑和身体. What they found was 那 exposure to UVB light 增加了 the 释放 of 这些 beta-endorphins. It caused 本质上 the 释放 of an endogenous pain killer. Now, a 秒 研究 那 came out 非常 recently, just 这 last 周 in fact, published in the journal Neuron, Cell Press journal, excellent journal, is entitled "A visual 回路 related to the periaqueductal gray area 对于 the antinociceptive effects of bright light treatment." I'll translate a little bit of 那 对于 你. The periaqueductal gray is a region of the midbrain 那 contains a lot of neurons 那 可以 释放 endogenous opioids, things like beta-enkephalin, things like enkephalin, things like mu opioid. 这些 are all names of chemicals 那 你的 身体 可以 manufacture 那 act as endogenous pain killers 和 增加 你的 tolerance 对于 pain.

安德鲁·休伯曼：

They actually make 你 feel 更少 pain overall by shutting down some of the neurons 那 perceive pain 或 by 减少 their activity, not to a dangerous 水平, right? They're not going to block the pain response so 那 你 burn yourself unnecessarily 或 harm yourself unnecessarily, 但 they act as a bit of a painkiller 从 the inside. If 你 heard the word antinociceptive, nociception is basically the perception 或 the way in which neurons respond to painful stimuli. So 你 可以 think of nociceptive events in 你的 神经系统 as painful events. 和 there I'm using a broad brush. I realize 那 the experts in pain 会 say, "Oh, it's not 确实 a pain 回路, et cetera, et cetera." 但 对于 sake of today's discussion, it's fair to say 那 nociception is the perception of pain. So if 这 title is "A visual 回路 related to the periaqueductal gray ... ," which is 这 area 那 releases 这些 endogenous opioids, "... 对于 the antinociceptive ... ," the antipain, "... effects of bright light treatment." The key finding of 这 研究 is 那 it is light landing on the eyes 和 captured by the 具体的 cells I was talking 关于 earlier, 那些 intrinsically photosensitive melanopsin ganglion cells is the long name 对于 them.

安德鲁·休伯曼：

但 这些 particular neurons in 你的 eye, 和 in my eye incidentally, 那 communicate 与 particular 大脑 areas. 这些 大脑 areas have names, if 你 want to know them, 对于 你 aficionados 或 对于 你 ultracurious folks, they have names like the ventral lateral geniculate nucleus 和 the intergeniculate leaflet. The names don't matter. The point is 那 light landing on the eyes is captured by 这些 melanopsin cells. They absorb 那 light, translate 那 light 进入 electrical signals 那 are handed off to areas of the 大脑, such as the ventral geniculate, 和 then the ventral geniculate communicates 与 这 periaqueductal gray area to evoke the 释放 of 这些 endogenous opioids 那 soothe 你 和 lead to 更少 perception of pain. 这 is a 确实 重要 研究 因为 it's long been known 那 in longer 天 或 in bright light environments, 我们 tolerate emotional 和 physical pain better. Previous 研究 had shown 那 it is light landing on 我们的 皮肤 那 mediates 那 effect, 但 only in part. It couldn't explain the entire effect.

安德鲁·休伯曼：

这 非常 recent 研究 indicates 那 it's also light arriving at the eyes, 和 in 这 case, again, UVB light, ultraviolet blue light of the sort 那 comes 从 sunlight, 那 is triggering 这些 antipain 或 pain-relieving 通路. So once again, 我们 have 二 parallel 通路. 这 is a theme 你're going to hear over 和 over 和 over again, not just in 这 episode 但 in all episodes of the Huberman Lab 播客, 因为 这 is the way 那 你的 大脑和身体 are built. Nature rarely relies on 一 mechanism in order to create an 重要 phenomenon, 和 pain relief is an 重要 phenomenon. So 我们 now have at least 二 examples of the potent effects of UVB light exposure to the 皮肤 和 to the eyes. 一 involving activation of testosterone 和 estrogen 通路, as it relates to mating, 和 another 那 relates to 减少 the total amount of pain 那 我们 experience in response to any painful stimuli.

安德鲁·休伯曼：

So 对于 那些 of 你 那 are thinking tools 和 方案, if 你're somebody who's experiencing chronic pain, provided 你 可以 do it safely, try to get some UVB exposure, ideally 从 sunlight. I think the 20-to-30-分钟 方案, 二 或 三 times per 周 is an excellent 一. Seems like a fairly low dose of UVB light exposure. It's hard to imagine getting much damage to the 皮肤. Of course, if 你 have 非常 sensitive 皮肤 或 if 你 live in an area of the world 那 is 非常, 非常 bright 和 has intense sunlight at particular times of year, 你'll want to be cautious. Heed the warnings 和 considerations 关于 sunscreen 那 I talked 关于 earlier, 或 关于 wearing a hat. 但 the point is 非常 clear. Most of us 应该 be getting 更多 UVB exposure 从 sunlight. I 可以 already hear the screams within the comments 或 rather the questions within the comments saying, "Well, what if I live in a part of the world where I don't get much UVB exposure?"

安德鲁·休伯曼：

和 I want to emphasize something 那 I've also emphasized in the many discussions on 这 podcast related to sleep 和 circadian rhythms 和 alertness, which is even on a cloud-covered 天, 你 are going to get far 更多 light 能量, photons, 通过 cloud cover than 你 are going to get 从 an indoor light source, an artificial light source. I 可以't emphasize 这 enough. If 你 look outside in the 早晨 和 你 see some sunlight, if 你 see some sunlight throughout the 天, 你 会 do yourself a great favor to try 和 chase some of 那 sunlight 和 get 进入 那 sunlight to expose 你的 eyes 和 你的 皮肤 to 那 sunlight as much as 你 safely 可以. 和 when I say as much as 你 safely 可以, 从不, ever look at any light, artificial sunlight 或 otherwise, 那's so bright 那 it's painful to look at.

安德鲁·休伯曼：

It's fine to get 那 light arriving on 你的 eyes indirectly. It's fine to wear eyeglasses 或 contact lenses. In fact, if 你 think 关于 the biology of the eye 和 the way 那 那些 lenses work, they 会 just serve to 专注 那 light onto the 非常 cells 那 你 want 那些 light beams to be delivered to. Whereas sunglasses 那 are highly reflective 或 trying to get 你的 sunlight exposure 通过 a windshield of a car 或 通过 a window simply won't work. I'm sorry to tell 你, 但 most windows are designed to filter out the UVB light. 和 if 你're somebody who's 确实 keen on blue blockers 和 你're wearing 你的 blue blockers all 天, well, don't wear them outside. 和 in fact, 你're probably doing yourself a disservice by wearing them in the 早晨 和 in the daytime. There certainly is a place 对于 blue blockers in the 晚上 和 nighttime if 你're having issues 与 falling 和 staying asleep.

安德鲁·休伯曼：

但 if 你 think 关于 it, blue blockers, what they're 确实 doing is blocking 那些 short wavelength, UVB wavelengths of light 那 你 so desperately need to arrive at 你的 retina 和, of course, also onto 你的 皮肤 in order to get 这些 powerful biological effects on 激素 和 on pain reduction. 和 in terms of 皮肤 exposure, 这些 数据 also 可能 make 你 think a little bit 关于 whether 或 not 你 应该 wear short sleeves 或 long sleeves, whether 或 not 你 want to wear shorts 或 a skirt 或 pants. It's all going to depend on the context of 你的 life 和 the social 和 other variables 那 are 重要. Of course, I don't know each 和 every 一 of 你的 circumstances, so I 可以't tell 你 to do X 或 Y 或 Z, nor 会 I. 但 你 可能 take 进入 consideration 那 it is the total amount of 皮肤 exposure 那 is going to allow ...

安德鲁·休伯曼：

那 it is the total amount of 皮肤 exposure, 那 is going to allow 你 to capture 更多 或 fewer photons, depending on, 对于 instance, if 你're completely cloaked in clothing 和 你're just exposed in the hands, neck 和 face, such as I am now, 或 whether 或 not 你're outside in shorts 和 a T-shirt. 你're going to get 非常, 非常 不同的 patterns of biological signaling activation in 那些 二 circumstances. Many of 你, I'm guessing, are wondering whether 或 not 你 应该 seek out UVB exposure throughout the entire year 或 only in the summer months, 和 那's sort of going to depend on whether 或 not 你 experience depression in the winter months, so-called seasonal affective disorder. Some 人们 have mild, some 人们 have severe forms of seasonal affective disorder. Some 人们 love the fall 和 winter 和 the shorter 天. They love bundling up. They love the leaves, they love the snow, they love the 寒冷, 和 they don't experience 那些 psychological lows.

安德鲁·休伯曼：

So it varies tremendously, 和 there are genetic differences 和 birthplace origin differences 那 relate to all 这, 但 确实 it has to be considered on a case-by-case basis. I personally believe, 和 这 was reinforced by the Director of the Chronobiology Unit at the National Institute of 心理健康, Samer Hattar, 那 我们 会 all do well to get 更多 UVB exposure 从 sunlight throughout the entire year, provided 我们 aren't burning 我们的 皮肤 或 damaging 我们的 eyes in some way. In addition to 那, 期间 the winter months, if 你 do experience some drop in 能量 或 增加 in depression 或 psychological lows, it 可以 be 非常 beneficial to access a SAD lamp, 或 if 你 don't want to buy a SAD lamp, 因为 oftentimes they 可以 be 非常 expensive, 你 可能 do well to simply get a LED lighting panel. I've described 一 之前, 和 I want to emphasize 那 I have no affiliation whatsoever to 这些 commercial sources. 但 I've described 一 之前 和 I'll describe it again, 和 我们 可以 provide a link to a couple examples of 这些 in the show note captions.

安德鲁·休伯曼：

这 is a 930-to-1000-lux light source 那's designed 对于 drawing. It's literally a drawing box. It's a thin panel; it's 关于 the size of a laptop. 非常 inexpensive compared to the typical SAD lamp. I actually have 一 和 I position on my desk all 天 long. I also happen to have skylights above my desk. I'm fairly sensitive to the effects of light, so on longer 天, I feel much better than I do on shorter 天. I've 从不 suffered 从 full-blown seasonal affective disorder, 但 I keep 那 light source on throughout the 天, throughout the year.

安德鲁·休伯曼：

但 I also make it a point to get outside 和 get sunlight early in the 早晨 和 several times throughout the 天. 和 if it's particularly overcast outside 或 there just doesn't seem to be a lot of sunlight coming 通过 那些 clouds, I 会 try to look at 那 light source a little bit 更多 each 天 in order to trigger 这些 mechanisms. Now, some 人们 may desire to get UVB exposure to their 皮肤, 和 they want to do 那 通过 sources other than sunlight. 和 there, it's a little bit 更多 complicated. There are, of course, tanning salons, which basically are beds of UVB light. 那's 确实 all they are. 从不 been to 一. I know 人们 do frequent them in certain parts of the world. There, of course, 人们 are covering their eyes. They are only getting UVB exposure to their 皮肤, 通常, 因为 the UVB exposure, 或 intensities rather, tends to be 非常, 非常 high.

安德鲁·休伯曼：

和 so 你 可以 actually damage 你的 eyes if 你're looking at a 非常, 非常 bright artificial UVB source up close. So 你 确实 have to explore 这些 options 对于 yourself. Sunlight, of course, being the original 和 still the best way to get UVB exposure. So 没有 knowing 你的 particular circumstances, finances, genetics, 或 place of origin, et cetera, I 可以't know whether 或 not 你 need to use artificial sources. 你're going to have to gauge 那. Meanwhile, getting outside, looking at 和 getting some exposure of UVB onto 你的 皮肤, is going to be beneficial 对于 the vast majority of 人们 out there. 和 in fact, it's even going to be beneficial 对于 人们 那 are blind. 人们 那 are blind, provided they still have eyes, 经常 maintain 这些 melanopsin cells. So even if 你're low vision 或 no vision, getting UVB exposure to 你的 eyes 可以 be 非常 beneficial 对于 sake of 情绪, 激素 通路, pain reduction 和 so forth.

安德鲁·休伯曼：

A cautionary note: 人们 who have retinitis pigmentosa, macular degeneration 或 glaucoma, as well as 人们 who are 尤其是 prone to 皮肤 cancers, 应该 definitely consult 与 你的 ophthalmologists 和 dermatologists 之前 你 start increasing the total amount of UVB exposure 那 你're getting 从 any source, sunlight 或 otherwise. There are additional 非常 interesting 和 powerful effects of UVB light, in particular on 免疫 function. All the organs of 我们的 身体 are inside 我们的 皮肤, 和 so information 关于 external conditions, meaning the environment 那 我们're in, needs to be communicated to the various organs of 我们的 身体. Some of them have 更多 direct access to what's going on outside. So, 对于 instance, the cells in 你的 大脑 那 reside right over the roof of 你的 mouth, 你的 hypothalamus, they control 激素 output 和 they control the biological functions 那 我们 call circadian functions, the 一 那 change every 24 小时, well, 那些 are just 一 或 二 connections, meaning synapses, away 从 那些 cells in 你的 eye 那 perceive UVB light.

安德鲁·休伯曼：

Other organs of 你的 身体, such as 你的 spleen, which is involved in the creation of molecules 和 cells 那 combat infection, well, 那些 are a long ways away 从 那些 cells in 你的 eye 和, in fact, they're a long ways away 从 你的 皮肤. There are beautiful 研究 showing 那 if 我们 get 更多 UVB exposure 从 sunlight 或 从 appropriate artificial sources, 那 spleen 和 免疫 function are enhanced. 和 there's a 非常 logical, well-established 回路 as to how 那 happens. 你的 大脑 actually connects to 你的 spleen. Now, it's not the case 那 你 可以 simply think, "Okay, spleen. Turn on, 释放 killer cells. Go out 和 combat infection." 然而, UVB light arriving on the eyes is known to trigger activation of the neurons within the so-called sympathetic 神经系统.

安德鲁·休伯曼：

这些 neurons are part of the larger thing 那 我们 call the autonomic 神经系统, meaning it's below, 或 not accessible by, conscious control. It's the thing 那 controls 你的 heartbeat, controls 你的 breathing, 和 那 also activates 或 flips on the switch of 你的 免疫系统. When 我们 get a lot of UVB light in 我们的 eyes, 或 I 应该 say sufficient UVB light in 我们的 eyes, a particular channel, a particular set of connections within the sympathetic 神经系统 is activated, 和 我们的 spleen deploys 免疫 cells 和 molecules 那 scavenge 对于 和 combat infection. So if 你've noticed 那 你 get fewer colds 和 flus 和 other forms of illness in the summer months, part of 那 could be 因为 of the 增加 in 温度 in 你的 environment, 因为 通常 longer 天 are associated 与 更多 warmth in 你的 environment, as opposed to winter 天, which are short 和 it tends to be colder out.

安德鲁·休伯曼：

Well, 那's true, 但 it's also the case the 人们 大约 你 have fewer colds 和 flus 和 那 你 会 get infected 与 fewer colds 和 flus 和 other infections, 因为 if 那些 infections, whether 或 not they're bacterial 或 viral, arrive in 你的 身体, if 你 inhale them 或 they get 进入 你的 mouth 或 on 你的 皮肤, 你的 spleen meets 那些 infections 与 a greater output. In other words, the soldiers of 你的 免疫系统, the chemicals 和 cell types of 你的 免疫系统 那 combat infection, are in a 更多 ready deployed stance, if 你 会. If 你 want to know 更多 关于 the 免疫系统 和 免疫 function, I did an entire episode 关于 the 免疫系统 和 the 大脑. 你 可以 find 那 at hubermanlab.com. 我们 talk 关于 cytokines, 我们 talk 关于 killer cells, B cells, T cells, et cetera. A lot of detail there.

安德鲁·休伯曼：

So 我们 经常 think 关于 the summer months 和 the spring months as fewer infections floating 大约. 但 in fact there aren't fewer infections floating 大约. 我们 are simply better at combating 那些 infections, 和, 因此, there's 更少 infection floating 大约. So 我们 are still confronted 与 a lot of infections. 我们're just able to combat them better. What does 这 mean in terms of a tool? What it means is 那 期间 the winter months, 我们 应该 be 尤其是 conscious of accessing UVB light to 增强 我们的 spleen function to make sure 那 我们的 sympathetic 神经系统 is activated to a sufficient 水平 to keep 我们的 免疫系统 deploying all 那些 killer T cells 和 B cells 和 cytokines, so 那 when 我们 encounter the infections, as 我们 inevitably 会, 我们're constantly being bombarded 与 potential infections, 那 我们 可以 combat 那些 infections well. 和 as just a brief aside, 但 I 应该 mention a brief aside 那's related to tens of thousands of quality 研究; it is well known 那 wound healing is faster when 我们 are getting sufficient UVB exposure.

安德鲁·休伯曼：

通常, 那's associated 与 the longer 天 of spring 和 summer. It is known 那 turnover of hair cells, the 非常 cells 那 give rise to hair cells are called stem cells. They live in little so-called niches in 我们的 皮肤 与 这些 hair stem cells, 和 你的 hair grows faster in longer 天. 那 too is triggered by UVB exposure, not just to the 皮肤 但 to the eyes. 那's right. There was a 研究 published in the Proceedings in the National Academy of Sciences a couple of years ago 那 showed 那 the exposure of 那些 melanopsin ganglion cells in 你的 eyes is absolutely critical 对于 triggering the turnover of stem cells in both the 皮肤 和 hair 和 also, it turns out, in nails. So if 你've noticed 那 你的 皮肤, 你的 hair 和 你的 nails look better 和 turn over 更多, meaning grow faster, in longer 天, 那 is not a coincidence, 那 is not just 你的 perception.

安德鲁·休伯曼：

In fact, hair grows 更多, 皮肤 turns over 更多, meaning it's going to look 更多 youthful. 你're going to 本质上 remove older 皮肤 cells 和 replace them 与 new cells. 和 all the renewing cells 和 组织 of 我们的 身体 are going to proliferate, are going to recreate themselves 更多 when 我们 are getting sufficient UVB light to 我们的 eyes 和 also to 我们的 皮肤. 和 so while some of 你 may think of light therapies such as red-light therapies 或 UVB therapies as kind of new agey, 或 just biohacking – again a phrase I don't particularly like, 这 notion of biohacking, 因为 it implies using 一 thing 对于 a purpose 那 it was 从不 intended to have. Well, it turns out 那 UVB exposure 和 red light, as 我们'll soon see, is a 非常 potent form of increasing things like wound healing 和 皮肤 health 对于 非常 logical, mechanistically backed reasons.

安德鲁·休伯曼：

So while I 可以't account 对于 everything 那's being promoted out there, in terms of 这 light source 会 help 你的 皮肤 look 更多 youthful 或 会 help heal 你的 scars, the mechanistic basis 对于 light having 那些 effects makes total sense. 但 what 你 应该 consider 然而, is 那 if the particular light therapy 那 你're considering involves 非常 local application rather than illuminating broad swaths of 皮肤, 和 if it has no involvement 与 the eyes, meaning there's no delivery of UVB 或 red light 或 the other light therapy to the eyes, it's probably not going to be as potent a treatment as 会 a 更多 systemic activation of larger areas of 皮肤 和 the eyes. Now, again, a cautionary note: I don't want 人们 taking technologies 那 were designed 对于 local application 和 beaming 那些 进入 the eyes. 那 could be 非常, 非常 bad 和 damaging to 你的 retinal 和 other 组织. Certainly wouldn't want 你 taking bright light of 非常 high intensity of any kind 和 getting cavalier 关于 那.

安德鲁·休伯曼：

通常, the local illumination of, say, a wound 或 particular patch of acne, 或 some other form of 皮肤 treatment, involves 非常 high-intensity light. 和 if the intensity is too high, 你 可以 actually damage 那 皮肤. 和 so as 我们'll talk 关于 in a few moments, most of 那些 therapies 对于 modifying 皮肤 involve actually burning off a small, 非常 thin layer at the top of the epidermis in efforts to trigger the renewal 或 the activation of stem cells 那 会 replenish 那 与 new cells. So there's a fine line to be had between light therapies 那 are 非常 localized 和 intense, which are designed to damage 皮肤 和 cause reactivation of new stem cells, whether 或 not it's hair cells 或 皮肤 cells, et cetera, versus systemic activation across broad swaths of 皮肤 in the eyes.

安德鲁·休伯曼：

你 确实 have to consider 这 on a case-by-case basis. 但 at least 对于 now, just consider 那 增加 in 激素, reduction in pain by way of 增加 in enkephalin 和 another endogenous opioids, improving 免疫 status by activating the spleen 和 so on 和 so on, 确实 are all the downstream consequence of illuminating large swaths of 皮肤 和 making sure 那 那些 neurons 和 within the eye get their adequate UVB exposure 或 other light wavelength exposure. Not simply beaming a particular wavelength of light at a particular location on the 身体 和 hoping 那 那 particular illumination at a particular location on the 身体 is going to somehow change the biology at 那 location. 我们的 biology just 确实 doesn't work 那 way. It's 可能, 但 in general, systemic effects 通过 broad-scale illumination 和 illumination to the eye, combined 与 local treatments, are 非常 可能 to be the ones 那 have the most success.

安德鲁·休伯曼：

Now I'd like to shift 我们的 注意力 to the effects of light on 情绪 更多 specifically. 我们 talked 关于 这 in terms of seasonal affective disorder, 但 many of us don't suffer 从 seasonal affective disorder. So I'd like to drill a little deeper 进入 how light impacts 情绪. 和 here I want to again paraphrase the statements of Dr. Samer Hattar at the National Institutes of 心理健康. I 应该 mention, the Director of the Chronobiology Unit at the National Institutes of 心理健康, 和 perhaps 一 of the top 一 to 二 to 三 world experts in how light 可以 impact 情绪, appetite, circadian rhythms 和 so forth. Samer stated on the podcast ,和 he said in various other venues as well, 那 getting as much UVB light in 我们的 eyes 和 on 我们的 皮肤 in the early 天 和 throughout the 天 as safely 可能 is going to be beneficial 对于 情绪. There's also another time of 天, 或 rather I 应该 say a time of 夜间, in which UVB 可以 be leveraged in order to 改善 情绪. 但 it's actually the inverse of everything 我们've been talking 关于 up until now.

安德鲁·休伯曼：

我们 have a particular neural 回路 那 originates 与 那些 melanopsin cells in 我们的 eye 那 bypass all the areas of the 大脑 associated 与 circadian clocks, so everything related to sleep 和 wakefulness, 那's specifically dedicated to the 通路 involving the 释放 of molecules like 多巴胺, the neuromodulator 那's associated 与 motivation, 与 feeling good, 与 feeling like there's possibility in the world 和 so on 和 so forth, 和 other molecules as well, including serotonin 和 some of 那些 endogenous opioids 那 我们 talked 关于 之前. 那 particular 通路 involves a 大脑 structure called the perihabenular nucleus. The perihabenular nucleus gets input 从 the cells in the eye 那 respond to UVB light, 和 frankly to bright light of other wavelengths as well, 因为 as 你 recall, if a light is bright enough, even if it's not UV 或 blue light, it 可以 activate 那些 cells in the eye.

安德鲁·休伯曼：

那些 cells in the eye communicate to the perihabenular nucleus. 和 as it turns out, if 这 通路 is activated at the wrong time of each 24-小时 cycle, 情绪 gets worse, 多巴胺 output gets worse. Molecules 那 are there specifically to make us feel good actually are reduced in their output. So while UVB exposure in the 早晨 和 throughout the 天 is going to be 非常 重要 对于 elevating 和 maintaining elevated 情绪, avoiding UVB light at 夜间 is actually a way in which 我们 可以 prevent activation of 这 eye-to-perihabenular 通路 那 可以 actually turn on depression. To be 非常 direct 和 succinct 关于 这, avoid exposure to UVB light 从 artificial sources between the 小时 of 10:00 p.m. 和 4:00 a.m. 和 if 你're somebody who suffers 从 low 情绪 和 overall has a kind of mild depression 或 even severe depression, of course please see a psychiatrist, see a trained psychologist. Get 那 treated.

安德鲁·休伯曼：

但 你 会 do 尤其是 well to avoid UVB exposure 从 artificial sources, not just 从 10:00 p.m. to 4:00 a.m., 但 确实 be careful 关于 getting too much exposure to UVB even in the late 晚上. So 8:00 p.m. perhaps to 4:00 a.m. I 可以't emphasize 这 enough 那 if 你 view UVB light, 你 activate 那些 neurons in 你的 eye 非常 potently. 和 if 那些 cells communicate to the perihabenular nucleus, which they do, 你 会 truncate 或 减少 the amount of 多巴胺 那 你 释放. So if 你 want to keep 你的 情绪 elevated, get a lot of UVB light throughout the 天. 和 at 夜间, 确实 be cautious 关于 getting UVB exposure 从 artificial sources.

安德鲁·休伯曼：

Now, let's say 你're somebody who has no issues 与 情绪. 你're just the happiest person all year long, 或 maybe 你 just have subtle variations in 你的 情绪. 你 feel great 关于 那. Turns out 那 你 still want to be 非常 careful 关于 light exposure between the 小时 of 10:00 p.m. 或 so 和 4:00 a.m., in fact, even 期间 sleep. There's a recent 研究 那 just came out in the proceedings of the National Academy of Sciences, 和 it's entitled "Light exposure 期间 sleep impairs cardiometabolic function." 这 is a 非常 interesting 研究 where they took human 受试者, young adults, 和 having them sleep in rooms 那 had 不同的 lighting conditions, either dim light 或 slightly bright light.

安德鲁·休伯曼：

Now, many 人们 可以't fall asleep in brightly lit rooms, so they acknowledged 这. 这些 were not 非常 brightly lit rooms. 这些 were rooms 那 had just a little bit of overhead room lighting, a hundred lux, which is not 非常 bright at all, 或 they had them sleep in a room 那 had 非常 dim light, which is 更少 than 三 lux. If 你 want to get a sense of how bright 三 lux is versus a hundred lux, I 会 encourage 你 to download the free app Light Meter. I have no relationship to the app. It's a pretty cool app 然而. I've used it 对于 a long time, where 你 可以 basically point 你的 phone at a particular light source, sun 或 otherwise, 和 你 just press the button. It'll give 你 an approximate readout of lux, which is the light intensity 那 the phone happens to be staring out at, at 那 location. It's not exact, 但 it's a pretty good back-of-the-envelope measure of light intensity.

安德鲁·休伯曼：

So 这些 受试者 were either sleeping in a 非常 dim room, 三 lux is 非常, 非常 dim, 或 a somewhat dim room, a hundred lux. In 这 研究, they measured things like melatonin 水平. They looked at 心率, they looked at measures of insulin 和 glucose management. Now, in previous episodes, I've talked 关于 how glucose, 血液 sugar, is regulated by insulin 因为 你 don't want 你的 glucose 水平 to be too high, hyperglycemia, 或 too low, hypoglycemia, 和 the 激素, insulin, is involved in sequestering 和 shuttling glucose in the bloodstream. Basically, how well 你 manage glucose in the bloodstream 可以 be indirectly measured by 你的 insulin 水平. 和 it's well-known 那 sleep deprivation 可以 disrupt glucose regulation by insulin.

安德鲁·休伯曼：

然而, in 这 研究, 受试者 were sleeping the whole 夜间 通过. It just so happens 那 some of the 受试者 were sleeping in 这 非常 dimly lit room, 三 lux, 和 other 受试者 were sleeping in a somewhat dimly lit room, a hundred lux. What's incredible 关于 这 研究 is 那 both rooms were sufficiently dimmed 那 melatonin 水平 were not altered in either case. 这 is 确实 key. It's not as if 一 group experienced a lot of bright light 通过 their eyelids 和 others did not. Melatonin 水平 were not disrupted. 和 given how potently light 可以 inhibit melatonin, 这 speaks to the fact 那 这 非常 dim condition of 三 lux 和 the somewhat dim condition of a hundred lux was not actually perceived by the 受试者, nor was it disrupting 这些 激素 通路.

安德鲁·休伯曼：

They also looked at glucose responses. They had 人们 本质上 take a fasting glucose test in 不同的 conditions. I won't go 进入 all the details. 但 here's what they found: In healthy adults, even just 一 夜间 of sleeping in a moderately lit environment, 这 hundred lux environment, caused changes, 增加 in nighttime 心率, which means 那 the sympathetic 神经系统 was overly active, as compared to 人们 那 slept in a completely dark 或 in a 非常 dimly lit room. 降低 in 心率 variability, 和 here I 应该 point out 那 心率 variability, 或 HRV, is a good thing. 我们 want 心率 variability. So they saw 增加 in 心率, 降低 in 心率 variability 和 增加 in next-早晨 insulin resistance, which is an indication 那 glucose management is suffering.

安德鲁·休伯曼：

So 这 is powerful. The 结果 of 这 研究 本质上 indicate 那 even just 一 夜间 of sleeping the whole 夜间 通过 in a dimly lit environment is disrupting the way 那 我们的 autonomic 神经系统 is functioning, altering so-called autonomic tone — making us 更少 relaxed is probably the best way to describe it, even though 我们 are asleep, disrupting the way 那 我们的 cardiometabolic function operates, such 那 我们 have lower 心率 variability 和 增加了 insulin resistance.

安德鲁·休伯曼：

这 is not a good thing 对于 any of us to experience. So while 我们've mainly been talking 关于 the positive effects of UVB light 和 other forms of light, now 我们 have 二 examples: 一 从 the work of Hattar 和 colleagues showing 那 UVB exposure via the perihabenula 可以 diminish the output of 多巴胺 和 other molecules 那 make us feel good if 那 UVB exposure is in the middle of the 夜间 或 late 晚上. 和 now 我们 have yet another 研究, performed in 这 case in humans, indicating 那 even if 我们 fall asleep 和 sleep the whole 夜间 通过, if the room 那 我们're sleeping in has too many lux, too much light 能量, 那 light 能量 is no doubt going 通过 the eyelids, which it 可以, activating the particular cells in the eye 那 trigger an 增加 in sympathetic 神经系统 activation 和 disrupting 我们的 代谢.

安德鲁·休伯曼：

和 这 研究 rests on a number of other recent 研究 published in Cell, which is a superb journal, 和 other journals, showing 那 期间 the course of a healthy, deep 夜间 sleep, 我们的 身体 actually transitions 通过 various forms of metabolic function. 我们 actually experience ketosis-like states. 我们 experience glucogenesis. 我们 experience 不同的 forms of 代谢 associated 与 不同的 stages of sleep. Not something 那 我们're going 进入 in-depth in 这 podcast. 我们 会 in a future podcast. What 这 研究 shows is 那 light exposure, even in sleep, is disrupting 我们的 autonomic, in 这 case the sympathetic arm of the autonomic 神经系统, in ways 那 are disrupting 代谢, probably in sleep, 但 certainly outside of sleep. So then 我们 wake up 和 have 我们的 首先 meal of the 天, 或 even if 你're intermittent fasting, 你 eat 那 首先 meal of the 天. If 你的 sleep is taking place in an environment 那's overly illuminated, well, 那's disrupting 你的 cardiac function 和 你的 代谢.

安德鲁·休伯曼：

I've been talking a lot 关于 UVB light, which is short-wavelength light, so UV light, blue light, maybe even some blue green light. 那's going to be short-wavelength light. Now I'd like to shift 我们的 注意力 to the other end of the spectrum, meaning the light spectrum, to talk 关于 red light 和 infrared light, which is long-wavelength light. Many so-called low-水平 light therapies — the acronym is LLLT, low-水平 light therapies — involve the use of red light 和 infrared light. Sometimes low-水平 light therapies involve the use of UVB, 但 更多 经常 than not, 这些 天 when 我们 hear LLLT, low-水平 light therapy, it's referring to red light 和 near-infrared light therapies.

安德鲁·休伯曼：

Low-水平 light therapies have been shown to be effective 对于 a huge number of biological phenomenon 和 medical treatments. I 可以't summarize all of 那些 now. It 会 take me many, many 小时. It 会 be an effective episode 对于 curing insomnia, 但 it wouldn't inform 你 properly 关于 the use of light 对于 你的 health. Rather, I'd like to just emphasize some of the top contour of 那些 研究 和 point out 那, 对于 instance, low-水平 light therapy 与 infrared light has been shown to be effective 对于 the treatment of acne 和 other sorts of 皮肤 lesions. There've been some 确实 nice 研究 actually where they use 受试者 as their own internal control. So 人们, believe it 或 not, agreed to have half of their face illuminated 与 red light 或 near-infrared light 和 the other half of their face serve as a control, 和 to do 那 对于 several 周 at a time. 和 你 可以 see pretty impressive reductions in 皮肤 lesions, reductions in scars 从 acne 和 reduction in acne lesions themselves, meaning the accumulation of new acne cysts, 与 low-水平 light therapy using red light 和 infrared light.

安德鲁·休伯曼：

Sometimes, 然而, there is a resistance of 那 acne to the low-水平 light therapy such 那 人们 会 get an initial improvement 和 then it'll go away despite continuing the treatment. So 你're probably asking, 或 at least 你 应该 be asking, "How is it 那 shining red light on 我们的 皮肤 可以 impact things like acne 和 wound healing, et cetera?" Well, to understand 那, 我们 have to think back to the beginning of the episode where I described how long-wavelength light, such as red light 和 near-infrared light, which is even longer than red light, 可以 pass 通过 certain surfaces, including 我们的 皮肤.

安德鲁·休伯曼：

So 我们的 皮肤 has an epidermis, which is on the outside, 和 the dermis, which is in the deeper layers. Red light 和 infrared light 可以 pass down 进入 the deeper layers of 我们的 皮肤 where it 可以 change the metabolic function of particular cells. So let's just take acne as an example. Within the dermis, the deep layers of 我们的 皮肤, 我们 have what are called sebaceous glands, 那 actually make the oil 那 is present in 我们的 皮肤. 那些 sebaceous glands are 经常 nearby hair follicles. So if 你've ever had an infected hair follicle, 那's not a coincidence, 那 hair follicles tend to get infected. Part of it is 因为 there's actually a portal down 和 大约 the hair follicle, 但 the sebaceous gland is where the oil is created 那 is going to give rise to, 对于 instance, acne lesions. Also in the dermis, in the deep layers of the 皮肤, are the melanocytes. They're not just in the epidermis, they're also in the deeper layers of the 皮肤. 和 你 have the stem cells 那 give rise to additional 皮肤 cells.

安德鲁·休伯曼：

If the top layers of the epidermis are damaged, 那些 stem cells 可以 become activated. 和 你 also have the stem cells 那 give rise to hair follicles. So by shining red light 或 near-infrared light on a localized patch of 皮肤, provided 那 red light is not of such high intensity 那 it burns the 皮肤, 但 is of sufficient intensity 那 provides just a little bit of damage to the upper layers of the 皮肤, the epidermis, 和 那 it triggers certain biological 通路 within the cells of the sebaceous gland 和 the stem cells within the hair cell niche 和 the stem cells in 皮肤, what happens is the top layers of the 皮肤 are basically burned off by a 非常 low 水平 of burn, 和/或 the cells in the deeper layer start to churn out new cells, which go 和 rescue the lesion, 本质上 clear out the lesion 和 replace 那 lesion 与 healthy 皮肤 cells.

安德鲁·休伯曼：

这 does work in the context of wound healing, getting scars to disappear. It also works to remove certain patches of pigmentation. There are sometimes cases where 人们 会 get a red blotchiness due to certain 皮肤 conditions, 或 some darker pigmentation 那 they want remover, 那 they need removed, 因为 it's a potential 皮肤 cancer threat. Now, how is red light actually doing it within the cells of the sebaceous gland, the stem cells, et cetera? Well, long-wavelength light 可以 actually get deep 进入 the 皮肤 — I mentioned 那 之前 — 但 可以 also get 进入 individual cells 和 可以 access the so-called organelles, which I described at the beginning of the episode. In particular, they 可以 access the mitochondria, which are responsible 对于 producing ATP.

安德鲁·休伯曼：

Now, the simple way to think 关于 这 对于 sake of 这 discussion is 那 as cells age, 和 in particular in 非常 metabolically active cells, they accumulate what are called ROSs, reactive oxygen species. 和 as reactive oxygen species go up, ATP 能量 production in 那些 cells tends to go down. It's a general statement, 但 it's a general statement 那 in most cases is true. There are some minor exceptions 那 don't concern us 那 have to do 与 cell types 不同的 than the ones 那 I'm talking 关于 now. So the way to think 关于 这 is 那 red light passes 进入 the deeper layers of the 皮肤, activates mitochondria, which 增加 ATP, 和 directly 或 indirectly 减少 这些 reactive oxygen species. 这些 reactive oxygen species are not good. 我们 don't want them. They cause cellular damage, cellular death, 和 对于 the most part just inhibit the way 那 我们的 cells work.

安德鲁·休伯曼：

So if 你've heard of red light 或 near-infrared light therapies designed to heal 皮肤 或 改善 皮肤 quality 或 remove lesions 或 get rid of scars 或 unwanted pigmentation, 那 is not pseudoscience, 那 is not woo science, 那 is grounded in the 非常 biology of how light interacts 与 mitochondria 和 reactive oxygen species. Some of 你 may also find it interesting to note 那 some of the cream-based treatments 对于 acne, 对于 instance, like retinoic acid, Retin-A, is actually a derivative of vitamin A. 和 the 通路 involving retinoic acid 和 vitamin A, believe it 或 not, is 非常 相似的 to the natural biological 通路 by which photopigments in the eye convert light information 进入 biological changes within 那些 cells.

安德鲁·休伯曼：

So the key point here is 那 light is activating particular 通路 和 cells 那 可以 either drive death of cells 或 可以 make 那些 cells 本质上 younger, by increasing ATP, by way of improving mitochondrial function. 和 in recent years, there have been some just beautiful examples 那 exist not only in the realm of 皮肤 biology 但 in the realm of 神经生物学, whereby red light 和 near-infrared light 可以 actually be used to 增强 the function of the cells 那, 对于 instance, allow us to see better 和, indeed, cells 那 allow us to think better. So now I'd like to review 那些 数据 因为 not only are they interesting in their own right, 但 they also point to some 非常 interesting 和 powerful application of low-cost 或 zero-cost tools 那 我们 可以 use to 改善 我们的 vision.

安德鲁·休伯曼：

If 你 are somebody who's interested in the use of red light 或 near-infrared light, so-called LLLT, low-水平 light therapies, 对于 treatment of dermatologic issues, so anything related to 皮肤, I 会 include a link to an excellent set of reviews. The 首先 一 is "Light-emitting diodes in dermatology: A systematic review of randomized controlled trials." 那 一 includes review of a 非常 large number of 研究. Came out just a few years ago, in 2018, 和 I think is 非常 clearly 和 cleanly laid out 对于 anyone to access. 和 你 可以 see the degree of effects of red light, 对于 instance, on treatment of acne 或 scarring, et cetera. 和 I'll also provide a link to another review, which is "Low-水平 light therapy in 皮肤: Stimulating, healing 和 restoring." So 对于 那些 of 你 那 are interested, again, in dermatologic issues 和 restoring youthfulness 和 the general themes of antiaging 和 longevity, 和 how red-light therapies 可以 be used 对于 那, I 会 encourage 你 to take a look at 那些 reviews.

安德鲁·休伯曼：

What 你're going to find is 那 rarely, if ever, is there a 研究 looking at whole-身体 red-light illumination 对于 sake of treating 和 improving 皮肤. 和 I mention 这 因为 I get a lot of questions 关于 infrared sauna 和 global illumination 与 red lights. 我们'll talk 更多 关于 cases where global illumination of 你的 whole 身体 或 你的 whole face 与 red lights 可能 be useful. 但 in terms of infrared sauna — I've mentioned on 这 podcast 之前, 和 I 会 certainly go deeper on 这 in an upcoming episode all 关于 the use of 热 和 温度 对于 augmenting 我们的 biology — in general, infrared saunas don't get hot enough 温度-wise in order to trigger some of the 重要 effects on growth 激素 和 热 shock proteins 和 some of the other things 那 sauna has been shown to be excellent 对于.

安德鲁·休伯曼：

那's a general statement. I realize there are some infrared saunas 那 do get hot enough. There are 非常 few 数据 on the use of whole-身体 illumination 与 infrared saunas 那 确实 point to any 具体的 mechanistically supported effects. Almost all the positive effects 那 你're going to see of red light 和 low-水平 light therapies, certainly the ones discussed in the reviews 那 I just mentioned, are going to be the consequence of 非常 directed illumination of particular patches of 皮肤 那 are seeking repair, 那 人们 are seeking the repair of. So again, I don't want to disparage infrared saunas. 但 in general, they don't get hot enough to trigger most of the positive effects 那 sauna have been demonstrated to have. 和 it's unclear at all as to whether 或 not they 可以 增强 皮肤 quality, youthfulness, restore top layers of 皮肤 那 are damaged, repair acne, et cetera. So 更多 on 热 saunas 和 infrared saunas 和 their comparison in an upcoming episode.

安德鲁·休伯曼：

So let's talk 关于 a clear set of examples where red light 和 near-infrared light have been shown to have positive effects on 我们的 health. 和 这些 are the 数据 那 I referred to at the beginning of the episode 从 Dr. Glen Jeffery at University College London, who, again, is a longstanding member of the neuroscience community, working on visual neuroscience, 和 who over the last decade 或 so has 确实 emphasized the exploration of red light 和 near-infrared light 对于 restoration of neuronal function as 我们 age. 这 is absolutely critical. 我们 know 那 我们 don't accumulate many new 大脑 cells as 我们 get older, 和 in some areas of 我们的 神经系统 such as 我们的 neural retina, which is the part of 我们的 eye 那's responsible 对于 translating light information to electrical signals so 那 我们 可以 see, 我们 don't get-

安德鲁·休伯曼：

Information to electrical signals so 那 我们 可以 see 我们 don't get any new cells 之后 the time in which 我们 are born. So the ability to keep 我们的 neurons healthy is extremely 重要 对于 我们的 visual 系统, extremely 重要 对于 我们的 hippocampus, an area the 大脑 involved in memory, 和 I 应该 just mention 那 even if 人们 don't get Alzheimer's, there's 总是 going to be some degree of age-related dementia. Sadly, nobody is as cognitively sharp in the years 之前 they die as they are 20 years 之前 那. It's just 从不 the case. 我们're all getting worse at thinking, feeling, perceiving, et cetera. The question is how quickly 我们 are getting worse. So any mechanism by which 我们 可以 preserve 或 reverse neuronal function turns out to be immensely beneficial.

安德鲁·休伯曼：

The Jeffrey Lab has published 二 研究 in recent years on humans 那 looked directly, no pun intended, at how red light 和 near-infrared light 可以 改善 visual function. I'm going to describe the parameters of 那些 研究 和 then I'm going to describe what they found exactly. The mechanistic motivation 对于 这些 研究, again, traces back to 这 effect of light on mitochondria. So to go a little bit deeper 进入 那 mechanism just briefly so 那 你 可以 frame any potential 方案 那 你 会 develop, when light arrives on cells, including neurons, 那 light 可以 penetrate 进入 the cells if it's of the appropriate wavelength. Red light 可以 do 那, 可以 get 进入 cells; it 可以 access the mitochondria; it 可以 增加 ATP. In general, anytime ATP is doing its thing to 增加 能量 in cells, it's involving 这 thing called cytochrome C, which is an oxidase. Anytime 你 hear "Ase," A-S-E, in biology, it's going to be an enzyme. It's involved in some process of degrading a molecule 和 creating another molecule 通常. So ATP 和 cytochrome C is going to give 你 ATP.

安德鲁·休伯曼：

Now 那's a great thing, 但 it creates a byproduct. It breaks things down such 那 你 get 这些 ROSs, 这些 reactive oxygen species, 和 那些 reactive oxygen species, 对于 那些 of 你 那 want to know, are involved in things like redox signaling, 和 reactive oxygen species actually change which genes are made in a cell. So the goal of any treatment to keep neurons 或 other cells youthful 和 functioning well, 和 to prevent 或 reverse aging, is going to be to 增加 ATP 和 to 减少 reactive oxygen species. 和 in doing so, to disrupt some of the normal 通路 associated 与 aging.

安德鲁·休伯曼：

The Jeffrey Lab approached 这些 研究 与 那 understanding of how mitochondria 和 reactive oxygen species in ATP work, 和 what they did was exquisitely simple to the point of being elegant. 和 what they found was 确实, 确实 exciting. What they did is they had 人们, 受试者 那 were either younger — so in their 20s — 或 40 years old 或 older, view red light of 关于 670 nanometers. 670 nanometers 会 appear red to 你 和 me. They had them do 那 at a distance 那 was safe 对于 their eyes, so at 关于 a foot away. Now, a foot away 从 a 非常 intense red light could actually be damaging to the eyes. So they had them do 这 at 关于 a foot away 从 a red light 那 was of low enough intensity 那 it did not damage the eyes, 和 they had them do 那 anywhere 从 二 to 三 分钟 per 天. 和 in 一 研究, they had them do 那 对于 a long period of time of 关于 12 周, 和 in the other 研究, they had them do 那 just 对于 a couple of 周.

安德鲁·休伯曼：

What's remarkable is 那 when 你 collapse the 结果 across 这些 二 研究, what they found is 那 when looking at 这些 受试者 ranging 从 28 years old to 关于 72 years old, the major findings were 那 in 个体 40 years old 或 older — so in the 40-to-72-year-old bracket, 但 not in the 受试者 younger than 40 years old — they saw an improvement in visual function. 那 improvement in visual function was an improvement in visual acuity, meaning the ability to resolve fine detail, 和 using a particular measure of visual function, which is called the Tritan exam, T-R-I-T-A-N, Tritan exam, which specifically addresses the function of the so-called short-wavelength cones, the ones 那 respond to green 和 blue light, they saw a 22% improvement in visual acuity, which in the landscape of visual testing is an extremely exciting result. So I think in most 研究 of improvements of vision, 你'd be 非常 excited to see an improvement of 5% 或 10%. So a 22% improvement in visual acuity, even though it's in 这 非常 具体的 form of visual testing, 这 Tritan exam, 或 这 Tritan score, well, 那 turns out to be 非常 significant 和 translates to the real world in an 重要 way.

安德鲁·休伯曼：

In particular, as 我们 age, 我们 tend to lose certain neurons within 我们的 retina, 但 我们 don't tend to lose cones. 我们 tend to lose rods. 我们 tend to lose other cells within the retina, including the cells 那 connect the eye to the 大脑, the so-called ganglion cells. Cones, 对于 whatever reason, are pretty resilient to age-related loss. 然而, 因为 rods 和 cones both are not just "among" the most metabolically active cells in 你的 entire 身体, 但 "the" most metabolically active cells in 你的 entire 身体 — 那's right, 你的 rods 和 cones are the cells 那 demand 和 那 use the most 能量 of all the cells in 你的 身体, not 你的 皮肤 cells, not 你的 spleen cells, not 你的 stomach cells. Even if 你 talk a lot, not the cells 那 are responsible 对于 moving 你的 mouth. it is the rods 和 cones of 你的 neural retina 那 are responsible 对于 using the most amount of ATP 和 能量 in 你的 entire 身体. 和 因为 of 那, 那些 cells tend to accumulate a lot of reactive oxygen species as 我们 age.

安德鲁·休伯曼：

Red light of the sort used in 这些 研究 was able to 减少 the amount of reactive oxygen species in the rods 和 cones 和 to rescue the function of 这 particular cone type, the short-wavelength 和 medium-wavelength cones. Which, if 你 think 关于 the 研究 is a little bit surprising 因为 it was red light 和 near-infrared light, not short-wavelength light 那 was used in order to create 这 improvement in cellular function.

安德鲁·休伯曼：

但 if 你 step back a little bit further, it makes perfect sense 因为 there's nothing 具体的 关于 the red light, in the sense 那 it's not 那 it gets delivered only to red cones. 那 red light 和 near-infrared light is being absorbed by all the photoreceptors within the eye: the rods, 和 the blue cones, 和 the green cones, 和 the red cones, it's just 那 the red cones absorb 那 light best. So the 重要 takeaway here is 那 viewing red light 和 near-infrared light at a distance at which it is safe, 对于 just a couple of 分钟 each 天, allowed a reversal of the aging process of 这些 neurons, which some 人们 have heard me say 之前, 和 I'll just say it again: the retina, including 你的 photoreceptors, are not just connected to 你的 大脑. They're not just near 你的 大脑, they are actual central 神经系统 组织. They are the only 二 pieces of 你的 大脑; neural retinas are the only 二 pieces of 你的 大脑 那 reside outside 你的 skull, 或 at least outside the cranial vault. So here 我们're seeing a reversal of the aging process in neurons by shining red light on 那些 neurons.

安德鲁·休伯曼：

Now of course, the Jeffrey Lab is primarily interested in vision, 和 humans are most dependent on vision as a sense to navigate the world 和 survive, so 这 is 确实 wonderful. Here 我们're looking at a therapy 那 可以 reverse age-related vision loss, at least in some 个体. 但 as 你 可以 imagine, the 研究 was also done on 这些 cells 因为 they reside outside the skull 和 你 可以 shine light directly on them, right? I'm sure 那 there are many 人们 out there who are interested in how they 可以 改善 the function, say, of the neurons in their 大脑 responsible 对于 memory. 和 in a few 分钟, I'll describe the noninvasive applications of light to try 和 restore the function of 那些 cells as well.

安德鲁·休伯曼：

So a little bit 更多 关于 the 研究 从 the Jeffrey Lab. 一 of the things 那 they observed was a reduction in so-called drusen, D-R-U-S-E-N. Drusen are little fatty deposits, little cholesterol deposits 那 accumulate in the eye as 我们 age. 我们've all heard 关于 cholesterol within 我们的 veins 和 arteries 和 how 那 可以 clog 我们的 veins 和 arteries, 和 how, of course, clogging of veins 和 arteries is not a good thing. Well, 我们的 neural retina being so metabolically active requires a lot of 血流, it's heavily vascularized, 和 drusen are a special form of cholesterol 那 accumulate in the eye. As it turns out, 这些 red light 和 near-infrared light therapies explored by the Jeffrey Lab were able to actually 减少 或 reverse some of the accumulation of drusen, 和 so in addition to 减少 reactive oxygen species, the idea in 心智 now is 那 red light may actually 减少 cholesterol deposits 和 reactive oxygen species in order to 改善 neuronal function.

安德鲁·休伯曼：

So, what 应该 你 和 I do 与 这些 结果, 或 应该 我们 do anything 与 这些 结果? Well, 首先 of all, I want to emphasize 那 even though 这些 研究 are 非常 exciting, they are fairly recent, 和 so 更多 数据, as 总是, are needed. There are some additional features of 这些 研究 那 I think are also 重要 to consider. 首先 of all, the exposure to red light needed to happen early in the 天, at least within the 首先 三 小时 of waking. How 会 一 do 那? Well, nowadays there are a number of 不同的 red light panels, 和 不同的 red light sources 那 certainly fall within the range of red light 和 near-infrared light 那 一 could use.

安德鲁·休伯曼：

I don't have any affiliation to any companies 或 products 那 promote 或 make 那些 red-light therapies. I do own a red light panel, so I confess I have started using 这 方案. I am older than 40 years old. I also have been experimenting 与 这些 red light panels as a way of addressing other changes in biological 组织 对于 which I'm doing 血液 work, et cetera, 和 I'm going to talk 关于 那 in a future episode, 但 那 of course is what I call anecdata — it only relates to my experience — so today, 和 certainly on all episodes of the Huberman Lab 播客, 我们 emphasize peer-reviewed 研究 almost exclusively, talking 关于 anecdata only when highlighting it as anecdata.

安德鲁·休伯曼：

So, if 你're somebody who wants to explore red-light therapy, here's what 你 need to do. 你 need to make sure 那 那 red light source, whatever source 你 happen to use, whether 或 not 你 purchase it 或 make 一. 和 in fact, 这些 red light sources are 非常, 非常 easy to make. 你 could 本质上 take a bright flashlight 和 cover it 与 a film 或 a filter 那 会 only allow particular long wavelengths to pass 通过. 这 会 be 非常 easy to look up online 和 figure out how to do 这. 你 could probably do 这 对于 just a few dollars, 或 你 could purchase a red light unit if 那 was within 你的 budget 和 something 那 你're interested in. 你 want to make sure 那 it's not so bright 那 你're damaging 你的 eye. A good rule of thumb is 那 something isn't painful to look at. 和 in fact, I 应该 just emphasize 那 any time 你 look at any light source, sunlight 或 otherwise, 那's painful, it makes 你 want to squint 或 close 你的 eyes, 那 means it's too bright to look at 没有 closing 你的 eyes. Okay, 那's sort of a duh.

安德鲁·休伯曼：

但 I 会 loathe to think 那 anyone 会 harm themselves 与 bright light in any way. I don't just say 那 to protect us, I say 那 to protect 你, of course, 因为 你 are responsible 对于 你的 health. 和 again, retinal neurons do not regenerate; once they are gone 和 dead, they do not come back. There's no technology to replace them at 这 current state in time so please don't damage 你的 retinas. So is a red light source safe to look at if it is not painful to look at? Chances are it is, 和 yet I 会 still encourage 你 to talk to 你的 optometrist 或 ophthalmologist 之前 getting 进入 any extensive 方案.

安德鲁·休伯曼：

但 if 你 were still determined to pursue the sorts of 方案 那 are in the Jeffrey 研究, certainly 我们'll provide a link to 那些 研究. Again, it involved looking at 这些 red light panels, blinking aloud 对于 二 分钟 to 三 分钟 every 早晨 对于 a period of 二 周 或 更多. 和 if 你're older than 40, 那 could 非常 well have an effect. If 你're younger than 40, 那's unlikely to have an effect. At least, 那 was what was observed in 这些 particular 研究. The lights were not flashing, it was continuous illumination. Again, 你're allowed to blink. It does not have to even be direct illumination; it 可以 be somewhat indirect illumination, much as 我们 described 对于 the use of UVB light 之前. The wavelength of light is 重要. It is red light 和 near-infrared light 那 is going to be effective in 这 scenario. The authors of 这 研究 emphasized 那 it was red light of 670 nanometer in wavelength 和 near-infrared light of 790 nanometers in wavelength 那 were effective 和 那 那些 wavelengths could be complementary.

安德鲁·休伯曼：

那's probably why, 或 maybe it's just coincidental, 但 it's a fortunate coincidence 那 a lot of the commercially available red light panels 那 你'll find out there combine both red light 和 near-infrared light. 然而, I want to emphasize 那 most of the panels 那 are commercially available are going to be too bright to safely look at 非常 close up. 和 in fact, 那's why most of 那些 red light panels are designed 对于 illumination of the 皮肤, 和 oftentimes arrive in their packaging 与 eye protectors 那 are actually designed to shield out all the red light. So take the potential dangers of excessive illumination of the eyes 与 any wavelength of light seriously. 但 if 你're going to explore 670 和 790 nanometer light 对于 sake of in 增强 neuronal function, set it at a distance 那's comfortable to look at 和 那 doesn't force 你 to squint 或 doesn't make 你 feel uncomfortable physically, as if 你 need to turn away 期间 the period of 那 二-to-三-分钟 illumination each 天.

安德鲁·休伯曼：

In terms of turning away 从 light, I'll just briefly mention 那 那 is not an accident 或 a coincidence 那 你 have 那 response to 非常 bright light. There is a so-called photic avoidance 通路 那 involves cells within 你的 retina, 这些 ganglion cells, 那 communicate 与 yet another 大脑 station, a certain area of 你的 thalamus, 那 communicate to areas of 你的 大脑 那 are associated 与 pain. So literally, 那 可以 trigger headache, 和 那 可以 trigger the squint reflex. Biology is just beautiful in 这 way. Too much light is bad 对于 us, in 那 it 可以 damage 我们的 eyes, 和 other aspects of 我们的 身体, so if 我们 look at a light 那's too bright, 我们的 eyes send a signal to the 大脑 那 gives us a sort of a headache 和 a desire to squint 和 turn away. So 那 可以 be a useful guide in terms of gauging how bright a light 应该 be, 或 at least how far away 你 应该 be 从 a bright source in order to safely engage 与 那 light source.

安德鲁·休伯曼：

So the 研究 I just described, once again involve the use of red light early in the 天, within 三 小时 of waking, 和 are 对于 the sake of improving neuronal function. Red light has also been shown to be beneficial late in the 天 和 even in the middle of the 夜间. 和 when I say middle of the 夜间, I'm referring to 研究 那 explore the use of red light 对于 shift workers. I know 那 most 人们 are not working in the middle of the 夜间, at least I hope they're not, 但 some of 你 may do 那 从 time to time. All-nighters 对于 studying. I confess, I still pull all-nighters every once in a while to prepare things like podcasts 和 other deadlines. 确实 try not to; happens 更少 和 更少 as I get older 因为 I think I get 更多 disciplined 和/或 更少 good at pulling all-nighters.

安德鲁·休伯曼：

但 I realize 那 many 人们 are doing shift work, where they have to work certainly past 10:00 p.m., 或 maybe they're taking care of young children in the middle of the 夜间 和 they have to be up. In 那 case, red light 可以 actually be 非常 beneficial. 和 nowadays, there are a lot of sources of red light available just as red light bulbs. 你 don't need a panel. So what I'm basically saying is 那 it 可以 be beneficial to use red lights at 夜间. The 研究 I'd like to emphasize in 这 context is entitled "Red Light: A novel, non-pharmacological intervention to promote alertness in shift workers." So, beautiful 研究; they explored the use of 不同的 wavelengths of light, so blue light of 460 nanometers, 或 red light, 或 dim white light of 不同的 brightnesses, et cetera, 和 looked at things like melatonin. How much does light of a given color 和 intensity suppress melatonin? They looked at cortisol, a 压力 激素. They looked at wakefulness. How much 或 to what degree could a given color of light 增加 wakefulness at 不同的 小时 of the 天?

安德鲁·休伯曼：

The takeaway 从 这 研究 is 非常 clear. If 你 need to be awake late at 夜间 对于 sake of shift work, 或 studying, 或 taking care of children, et cetera, red light is going to be 你的 best choice. 因为 if the red light is sufficiently dim, it's not going to inhibit melatonin production 和 it's not going to 增加 cortisol at 夜间. Cortisol 应该 be high early in the 天, 或 at least 应该 be elevated relative to other times a 天 if 你 are healthy. A late-shifted 增加 in cortisol, 然而 — 9:00 p.m. cortisol, 10:00 p.m. cortisol — is well-known to be associated 与 depression 和 other aspects of 心理健康, 或 I 应该 say mental illness. So if 你 do need to be awake at 夜间, 或 even all 夜间, red light is going to be the preferred light source.

安德鲁·休伯曼：

和 in terms of how bright to make it, well, as dim as 你 可以 while still being able to perform the activities 那 你 need to perform, 那's going to be 你的 best guide. I'll provide a link to 这 研究 as well. Again, it's a 确实 重要 研究 因为 it emphasized 那 there are forms of light, red light, provided it's dim, 那 可以 allow 你 to stimulate the alertness 那 light landing on the eyes 可以 provide. So it allows 你 to stay awake 和 to do whatever work 那 你 need to do. It does not seem to alter melatonin production, so 那's good. It does not seem to alter 水平 或 timing of cortisol production. So yet another case where red light, used correctly, 可以 be beneficial.

安德鲁·休伯曼：

Up until now, 我们've been talking 关于 the effects of shining 不同的 wavelengths of light on the 皮肤 或 on 我们的 eyes, 和 the downstream health consequences of 那 illumination. 然而, 一 of the most 重要 goals of science 和 medicine is to figure out how to change the health of 我们的 大脑. 和 of course, 我们的 大脑 is contained within 我们的 skull, 和 因此 我们 可以't just shine light onto the outside of 我们的 head 和 expect it to change the activity of neurons deep within the 大脑, unless 那些 neurons are linked up 与 我们的 eyes 或 与 我们的 皮肤. 和 as it turns out, even though there are a lot of 大脑 areas 那 are connected 通过 neural 回路, 和 激素 回路, 通过 我们的 eye, 和 believe it 或 not, also to 我们的 皮肤, many 大脑 areas are not.

安德鲁·休伯曼：

大脑 areas such as the hippocampus, which is involved in learning 和 memory, 大脑 areas such as 我们的 neocortex. Well, some areas of 我们的 neocortex, such as 我们的 visual cortex, are indirectly linked to 我们的 eyes, so if 我们 shine light in 我们的 eyes, 我们 可以 change the activity of neurons in 我们的 neocortex. 但 there are other 大脑 areas 那 are not directly 或 even indirectly connected to 我们的 visual 系统, not at least in any immediate way. So 那 raises the question of how do 你 change the activity of neurons in the 大脑? Well, there's pharmacology. 你 可以 take pills, 你 可以 inject drugs, 那 会 change the pharmacology of neurons 和 the way they operate 和 fire. Of course, antidepressants are 一 such instance. Opioid drugs are another. There's a huge array of psychoactive compounds, meaning compounds 那 会 change the 水平 of chemicals in 你的 大脑. Some of 那些 work, many of them also carry side effects. It's all rather indirect, meaning 你 have lots of 不同的 cells in 不同的 areas of 你的 大脑 那 utilize the same chemicals. So a drug, 对于 instance, to 增加 serotonin 对于 sake of improving depression, 会 also 经常 have the effect of 减少 certain neurons' output of serotonin in the hippocampus 和 cause changes in appetite, 或 changes in libido 和 so on 和 so forth.

安德鲁·休伯曼：

你 could imagine using electrical stimulation; putting wires 进入 the 大脑 和 stimulating 具体的 大脑 areas in order to activate the neurons in 那些 大脑 areas. 和 certainly 那 works, 和 has been done experimentally 和 is done 期间 neurosurgery exams, et cetera, 但 involves removing a piece of skull. So 那's not 非常 practical. In principle, light 会 be a wonderful way to modulate the activity of neurons deep within the 大脑. 但 again, the skull is in the way. Recent 研究, 然而, have figured out ways 那 light 可以 be delivered to the eyes to change global patterns of firing in the 大脑 in ways 那 可以 be beneficial to the 大脑.

安德鲁·休伯曼：

和 the work 那 I'm referring to now is mainly the work of Li-Huei Tsai at MIT, Massachusetts Institute of Technology 和 her colleagues. 和 what they've discovered is 那 there's a particular pattern of 大脑 activity called gamma activity. Gamma activity is 一 so-called wavelength of electrical activity in the 大脑. So not wavelengths of light, 但 wavelengths of electrical activity in the 大脑 那 可以 be restorative 对于 certain aspects of learning 和 memory, 和 可以 actually help create molecular changes in neurons 那 lead to clearance of debris 和 even reductions in age-related cognitive decline. So, the way to think 关于 大脑 waves 和 大脑 oscillations is 那 neurons are electrically active; 那 involves chemicals, et cetera; 和 they 可以 be active in 非常 slow, big wave forms. So 你 可以 think of delta waves, meaning, so 你 可以 imagine a wave of electrical activity 那 comes along 非常 infrequently. So a given neuron fires, 和 then some period of time later, fires, 和 then some period of time, even later, fires. 或 你 可以 imagine 那 那 same cell is 非常 active; fires, fires, fires, fires, fires. 你 可以 imagine if it's firing 非常 经常, it's going to be short wavelength, right? Shorter gaps between firing, 或 if it's firing 非常 seldom, 你're going to think 关于 那 as longer wavelength firing.

安德鲁·休伯曼：

Turns out 那 gamma waves are 一 pattern of firing 那 lead to downstream metabolic functions 和 biological functions 那 end up clearing away debris 那's associated 与 aging in cells. 和 那 also lead to molecular changes 那 增强 the kind of youthfulness of neurons, so to speak. How do 我们 induce gamma oscillations within the 大脑? Well, what Li-Huei Tsai 和 colleagues have beautifully shown is 那 by delivering certain patterns of light flicker, so lights going on 和 off at a particular frequency, the 大脑 as a whole starts to entrain, meaning it matches to 那些 particular patterns of light flicker, even though many of the 大脑 areas 那 do 这 are not directly within the visual 系统 或 visual 通路.

安德鲁·休伯曼：

So the 研究 那 I'm referred to are several, 但 the 一 那 I'd like to highlight is entitled "Gamma entrainment binds higher-order 大脑 regions 和 offers neuroprotection." What they 本质上 did was to expose 受试者 to 40 hertz, which is a particular frequency of illumination to the eyes. So it's light goes on, light goes off, light goes on, light goes off, at a frequency of 40 hertz. 和 when they did 那 和 they recorded the activity of neurons within the 大脑, not just within the visual areas of the 大脑, 但 within other areas as well, they observed 增加了 gamma oscillations, meaning 那 the electrical activity of the 大脑 at large started to match to the patterns of light 那 were delivered to the eyes.

安德鲁·休伯曼：

这 is 确实 exciting 和 非常 unique 从 the 不同的 types of phototherapies 那 我们've been talking 关于 up until now. All the patterns of phototherapy 那 我们've been talking 关于 up until now involved constant illumination 与 a given wavelength. Here, it is wavelength generating patterns of illumination. Light on, light off, light on, light off, at a particular frequency. So what they found, 对于 instance, using 这 pattern of stimulation — 和 by the way, the stimulation was called genus gamma entrainment using sensory stimulation; so G-E-N-U-S gamma entrainment using sensory stimulation — had a number of 确实 interesting effects.

安德鲁·休伯曼：

首先 of all, it reduced so-called amyloid plaques 和 phosphorylated tau, amyloid plaques 和 phosphorylated tau are associated 与 Alzheimer's 和 normal age-related cognitive decline. So 这 is incredible, right? A pattern of flashing light delivered to the eyes creates a pattern of neuronal firing, not just in the visual areas of the 大脑, 但 in other areas of the 大脑 as well, 那 in turn, trigger molecular 通路 那 减少 some of the markers 和 the cause of age-related cognitive decline in Alzheimer's.

安德鲁·休伯曼：

和 in parallel to 那, they observed an upregulation of some of the biological 通路 那 lead to enhancement of neuronal function, maintenance of synapses, which are the connections between neurons, 和 so on 和 so on. They have discovered 和 list out a huge number of 这些 biological effects, both the reduction in bad things, so to speak, 和 the improvement in good biological 通路. 和 I find 这些 研究 so exciting 因为 首先 of all, they're noninvasive, right? There's no drilling 通过 the skull. They are 非常 tractable in the experimental sense, meaning 那 你 could imagine 那 if 40-hertz stimulation turns out to be the 非常 best stimulation 方案 to induce 这些 gamma oscillations, well great, 但 因为 it's noninvasive, it's fairly easy to explore 50-hertz stimulation, 100-hertz stimulation, 20-hertz stimulation, 和 to do 那 与 不同的 wavelengths of light.

安德鲁·休伯曼：

和 so, 那's what's happening now. The CyLab 和 other labs are 确实 starting to explore the full range of variables 那 可以 impact oscillations within the 大脑 和 their downstream consequences. So again, 这 is phototherapy, 但 phototherapy of a 非常 不同的 sort 那 我们've been talking 关于 up until now. It's phototherapy designed to trigger activation of biological 通路 far away 从 the 非常 组织 那's being illuminated. 和 it calls to 心智 the same sorts of mechanisms 那 我们 were talking 关于 earlier, where illumination of the 皮肤 与 UVB light is setting off an enormous number of 不同的 cascades in 不同的 organs 和 组织, including the spleen, the testes, the ovaries, 和 so on. So again, light has 这些 powerful effects both locally on the cells 那 the light is delivered to, 但 also systemically in terms of the cells 那 are changing their electrical 和 chemical outputs are modifying lots 和 lots of biological programs.

安德鲁·休伯曼：

Is there an actionable tool related to 这些 研究 yet? Well, 那 sort of depends on how adventurous 你 are. Right now, 这些 研究 are being explored in the context of clinical trials in 人们 与 Alzheimer's, dementia 和 other forms of neurodegeneration. Is it dangerous to look at a 40-hertz flickering light? Well, in general, the answer is going to be no. 然而, if 你're prone to epilepsy, 对于 instance, staring at a flickering light of a given continuous frequency 可以 induce seizure, right? 那 可能 surprise some of 你, 但 it shouldn't 因为 as 这 研究 illustrates, 和 as anyone who's ever been out at 夜间 to a club 或 something illustrates, when 你 look at a strobe light, 对于 instance, 你的 whole world of visual perception changes, 但 actually the rhythm at which 你 perceive music, at which 你 perceive conversation, at which 你 perceive the movement of 你的 身体 actually changes according to the patterns of visual flicker. In most cases, strobe, if 我们're using the sort of club dancing example, 你的 大脑 is entraining to its outside environment.

安德鲁·休伯曼：

So given the power of flickering lights to entrain 大脑 rhythms, I think at 这 stage it's probably too preliminary to 确实 suggest a 具体的 方案, 但 I 会 definitely keep an eye out 对于 这些 sorts of 研究. They are coming out all the time, 和 I think in a 非常 short period, 我们 are going to see 具体的 方案 那 一 could potentially use even at home, 和, of course, 这些 are noninvasive 方案 in order to place the 大脑 进入 a particular state, not just 对于 sake of offsetting neurodegeneration, 但 also 对于 增强 专注, 对于 增强 the transition 进入 sleep 和 other 大脑 states as well.

安德鲁·休伯曼：

Today, I covered what I 会 say is a lot of information. My goal was to give 你 an understanding of how light 可以 be used to change the activities of cells, organelles within 那些 cells, entire organs, 和 how 那 可以 happen locally 和 systemically. 我们 talked 关于 the power of light to impact 我们的 biology at the endocrine 水平, neuronal 水平, 免疫 水平, 情绪, et cetera 通过 both illumination of the eyes, 和 the 皮肤 和 other 组织 as well.

安德鲁·休伯曼：

I realized 那 even though 这 was a lot of information, there are many aspects of phototherapy 那 I did not cover. I know there's a lot of interest nowadays, 对于 instance, in the use of red light 和 other wavelength light therapies 对于 ovarian health 和 testicular health. In fact, I get a lot of questions such as, "可以 red light be used to 改善 testosterone output? 和 if so, is 那 best accomplished by shining red light on the 皮肤 或 directly on the gonads, on the testicles?" I'm going to cover 那些 数据 at a future time. Right now, the 研究 那 have been done in rodents, I don't think are easily enough translated to humans, 和 the 研究 那 are happening in humans now are exciting in the sense 那 they hold a lot of potential, 但 the 数据 aren't clear yet.

安德鲁·休伯曼：

然而, the 数据 using UVB on the 皮肤 of men 和 women in order to 增加 激素, in particular testosterone 和 estrogen output, 那些 数据 I think are 非常 exciting 和 非常 actionable when 我们 talked 关于 那些 earlier. So if 你 want 更多 information on how phototherapy 可以 be used, certainly 我们 会 do another episode on phototherapy in 这些 other contexts.

安德鲁·休伯曼：

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安德鲁·休伯曼：

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