Behaviors That Alter Your Genes to Improve Your Health & Performance | Dr. Melissa Ilardo

The conversation opens with a broad question about nature and nurture: how much of human ability and appearance is fixed, and how much can behavior or environment alter gene expression? Ilardo says the field is still learning. Environmental signals can change gene expression, but the interview does not put a single percentage or boundary on what is modifiable; it distinguishes traits encoded in genes from expression that may be more responsive.

Eye color serves as an example of inherited variation. Ilardo recounts the claim that all blue-eyed people descend from one person whose eye color changed, and Huberman frames that person as the first-generation blue-eyed individual. They discuss brown as the original eye color and green as possibly arising in multiple people through different genes. These are presented as conversational genetics facts rather than evidence examined in the episode: no study, date, or mechanism is supplied here.

The speakers then revisit the idea that eye color is entirely beyond behavioral influence. Huberman suggests that eyes can darken with age and ultraviolet exposure, using blue-eyed babies as an example. Ilardo says she had not heard that claim and finds it interesting; the exchange offers no supporting evidence or clear distinction between developmental change, pigmentation, and environmental effect. The point therefore remains a hypothesis within this conversation, not a conclusion established by the discussion.

Ilardo describes gene expression as responsive to environmental inputs on timescales of minutes or hours, while also noting that some epigenetic modifications can persist across generations. She characterizes these modifications as molecules attaching to the genome and changing gene expression. As an example, she refers to changes observed in refugee populations and says descendants may inherit changes even when they did not experience the event that displaced their parents. The interview does not identify the specific modifications, measures, or studies behind that example, so the scope and mechanism are left open.

Ilardo separates changes in gene expression from changes in the frequency of genetic variants. She says the Dutch famine has been associated with epigenetic changes that may have helped people survive food scarcity, while noting that a response advantageous during famine might be less useful when food is abundant. She then describes population-level genetic change through new mutations or variants already present becoming more common. In her account, some such changes may spread over roughly one or two thousand years, faster than the five or ten thousand years once assumed. The famine example is presented briefly; this segment does not specify the studies or establish that the epigenetic response was adaptive.

The discussion turns to mate choice and immune-system diversity. Huberman recalls a mouse-choice account involving the major histocompatibility complex (MHC), while acknowledging that he is unsure whether the evidence still holds. Ilardo says a similar human study asked heterosexual participants to smell sweaty T-shirts worn by members of the opposite sex and rate their attraction. As she describes it, participants tended to prefer the smell of people whose immune-system genes, particularly the MHC, differed from their own. The interview does not provide the study design details or effect size, and odor ratings alone do not establish actual partner choice, reproductive outcomes, or healthier offspring.

Huberman interprets smell as a possible, largely unconscious cue related to the immune genes a future child might inherit. Ilardo agrees that this could be relevant, but the conversation moves from the reported attraction study to a broader evolutionary interpretation without presenting direct evidence that smell preferences produce those offspring outcomes. Their use of “hybrid vigor” is tentative: they are exploring whether genetic differences can affect compatibility, not claiming a demonstrated general benefit from pairing people with more distant ancestry.