Rowan Jacobsen

The conversation opens on what Rogan calls a confusing question: if the sun gives you vitamin D, why does it cause skin cancer, and if it causes skin cancer, how can it be good for you? Jacobsen agrees that the subject is "super complicated". He says the official messaging has not admitted that complexity, and that this gap was a major reason he wrote his book.

Jacobsen says he started out with the institutional view that sun exposure was very bad. Even then, his instinct doubted it, because being in the sun in Vermont made him feel good. He backs that feeling with a physiological claim: "we now know that it literally triggers the release of opiates in the brain." Rogan then asks what research changed his mind.

He traces the change to a science journalism fellowship about seven or eight years ago. During it, he read studies on opiate release, studies suggesting cognition improves when light hits the skin, and findings that metabolism "cranks up a little bit" when the body senses sunlight. A couple of other studies seemed to indicate that sunlight could lower blood pressure. He names none of these studies in this part of the interview, and he says he still held the view "sunlight bad" at that point.

His revised position is a qualified one. Sunlight does increase skin cancer risk, and "in general, too much sun increases your risk of skin cancer." But he argues that the relationship is not necessarily linear and depends on the type of skin cancer. The open questions he lists are confounding factors, how skin cancer compares with other diseases, and how any protection sunlight gives against other diseases weighs against the skin cancer risk.

So it's not the type of thing that can, you know, be done in a 30-second PSA.

Asked what causes sun-related skin cancer, Jacobsen points to ultraviolet light, which he calls "the most energy-intense part of the solar spectrum." He explains that we absorb all wavelengths of light to some degree, and that high-energy UV photons enter the skin. The transcript breaks off mid-explanation. The next passage picks up with "So that's why it could cause skin cancer", and later he describes UV as light "that can screw up your DNA." He dates this understanding to roughly the 1940s and 1950s, when scientists began to worry about how much sun people were getting.

Rogan notes that this view was not universal and asks when science learned that sunlight makes vitamin D. Jacobsen places that discovery in the 1920s and calls it a big part of the story. A little earlier, researchers had realized that sunlight could prevent rickets.

Jacobsen describes rickets as a soft-bone disease in children who do not get enough calcium into their bones. In his telling, farm children never got it. During the Industrial Revolution, children working in factories and living in tenements in cities "choked with coal smog" stopped seeing the sun and began developing rickets in the late 1800s. When Rogan asks whether nutrition was a factor, Jacobsen answers that "It was all vitamin D". He adds that it was at first thought to be a vitamin issue, and that working out how to cure rickets is how vitamin D was discovered.

He tells the story of a dog experiment, which he places hesitantly in Scotland ("this is, I think, Scotland"). Researchers had noticed that rural children did not get rickets while city children did. One researcher kept dogs indoors and fed them oatmeal, the common Scottish diet of the time. The dogs got rickets, and he concluded the cause was dietary. Jacobsen says the researcher "got lucky" because he had also deprived the dogs of sunlight, which was the real cause.

The mechanism he describes ties the two sides of the sun debate together. UV light hits cholesterol molecules in the skin and breaks a bond, letting the molecule flip into a new form, which is vitamin D. So the same ultraviolet light that can damage DNA also produces vitamin D, which he calls "downstream of cholesterol."

Once the vitamin D link was known, Jacobsen says, the pendulum swung hard the other way. Through the 1920s, 1930s and into the 1940s, sunlight was seen as a cure for everything. He describes parents sending children to heliotherapy institutes in the Swiss Alps, where children skied and took classes in their underwear and instructors taught outdoors dressed the same way. He says photos from the period show everyone looking "really healthy," and that the prevailing idea was that you couldn't get too much light. The conversation connects this belief to people "literally burning themselves on purpose for health."

Asked whether burning is a big part of the problem, Jacobsen draws a distinction he sets up as central to his argument. He presents it as the current state of the evidence for melanoma, the most dangerous skin cancer, while noting that "it looks like" this is the case.

it's associated with burning strongly, but not with like gentle, moderate everyday sun exposure.

Rogan asks how much skin type matters, naming pale skin, freckles, and red or blonde hair, and whether gradual exposure can reduce the risk. Jacobsen answers: "skin type is kind of everything." He says people with very dark skin "basically don't get sun-induced skin cancer, almost never." He argues that authorities avoid saying so because they want one-size-fits-all recommendations, and that advice to always avoid the sun is written for very fair people.

He singles out people with red hair and orange freckles. He says they carry a mutation in a melanin gene that makes them highly susceptible to sun-induced skin cancer. People with that phenotype, which he describes as many moles, red hair and freckles, "do have to be really careful." He adds that they cannot tan much anyway. Everyone else, he says, is much less susceptible and can make more melanin fairly easily by tanning.

Later in the segment he quantifies melanin's protection. In people with very dark skin, such as those of African ancestry, he says melanin absorbs "like, 97, 98% of the UV rays." Rogan pushes back with an exception: "didn't Bob Marley die from skin cancer?" Jacobsen confirms that Marley did, and they return to the case later: Jacobsen describes Marley’s toe melanoma as a type not caused by sun exposure.

Rogan brings up a peptide people are taking to darken their skin. Jacobsen says he doesn't know exactly what is happening with it and offers two possibilities. The peptide might act like a photosensitizer, making skin absorb solar radiation "not necessarily in a good way" so that the body makes extra melanin to compensate. Or it might trigger melanin production independently of sunlight.

The speakers look the compound up with the AI search tool Perplexity and read the result aloud. It identifies the peptide as melanotan, a synthetic analog of melanocyte-stimulating hormone. It says the peptide is largely unregulated, illegal in many regions for cosmetic use, and not FDA-approved for cosmetic use. The listed risks are purity problems from the unregulated market, rapid and uneven darkening of existing moles, new moles, and hyperpigmentation, which it says "could mask or accelerate the development of melanoma." It also lists prolonged, painful and "potentially damaging" erections. According to the result, medical and dermatological organizations strongly advise against melanotan because it is unapproved and has no clinically established safe dosages. Jacobsen finds this strange, since the molecule it mimics, alpha-MSH, is how the body normally makes melanin.

The two are skeptical as they look at before-and-after photos online. Rogan notes that "it's Instagram you never know what's real" and points out that lighting differs between shots. Another image is dismissed as looking like it came from a poor early phone camera. He compares one result to bodybuilders who dye their skin darker so their muscles stand out. They then find what they consider better photos in a user's tanning log.

Rogan wonders whether a regulated version, given at a studied dose, could protect pale people. Jacobsen agrees that real melanin would protect the skin and that "Melanin clearly protects you from skin cancer." Rogan asks for an example of a pale person who took it. They look at one set of photos that seems to show the same person and the same mole, though they find the face hard to make out. Jacobsen then names the limitation: a product like this would be easy to market deceptively, and "this is part of the unregulated market problem."

you're getting 99% bro science on this stuff

Jacobsen contrasts the shortcut with gradual natural tanning. He argues that a little sun every day, slowly increased, does more than make melanin. It also ramps up the body's damage-repair systems, such as nucleotide excision repair, which fixes DNA and damaged cells. He compares this to exercise and frames it as hormesis, where mild stress primes the body's defenses. His suggestion is that melanin and repair capacity should rise together. Rogan extends this to a hypothetical: if studies ever established a safe, effective dose, the peptide would ideally be paired with slow sun exposure. Neither cites research on this pairing.

They read one user's self-report, posted about 14 years earlier. The user claimed to be "pretty much impervious to UV at this point" and said they had "faded about 25%" since returning from Florida, with plans to dose again in March. The side effects listed were decreased appetite and very mild nausea, with the user adding "more for some, none for me." The user said they had not noticed much change in libido or any facial flushing, and that stretching felt unusually good. Wondering whether the user is still alive, the speakers find the account was active about a year ago, while allowing that someone else could be running it. They stop browsing the person's profile after noticing other forum activity. This is a single anecdote, not evidence of safety.

One aside in the same stretch notes that, in theory, one could tan using an old-school quartz tanning lamp. The remark is not developed.

Discussing why only risk-takers try such products, Rogan recalls a man who appeared on Oprah "or one of those shows." The man took colloidal silver, and his skin turned permanently blue. Rogan first says "I believe he died young" without knowing whether the silver killed him. The lookup they read describes argyria, a rare condition in which silver builds up in the body and discolors the skin, and says the man died in 2013 "from unrelated causes." Rogan responds, "Whatever that means," and suggests that anyone taking that much colloidal silver is probably making other risky choices too. The exchange is mostly joking and makes no health claims beyond what the lookup says.