This is one of those topics where the mechanism matters more than the headline. The claim isn't "cold makes you more fertile." That would be too clean, too marketable, and too wrong. The actual claim is more nuanced and, I think, more useful: cold exposure can support fertility by reducing heat for men, and by regulating the stress hormone cascade for both men and women. Two different pathways. Neither of them obvious.
For men, the logic is almost architectural. The testes sit outside the body for a reason — sperm production requires a temperature about four degrees below core body temperature. When that thermal gradient collapses, sperm quality drops. Varicoceles are the classic culprit: essentially varicose veins in the testicular region that cause blood to pool, raising local temperature and impairing spermatogenesis. Cold exposure doesn't supercharge testosterone or magically improve sperm morphology. It simply restores the environment those cells need to develop properly. It's remediation, not enhancement. That distinction matters.
The female side of this equation is more complicated, and I want to be honest about the nuance here. We have a 2025 paper in the knowledge base on cold environment exposure and female reproductive health that adds important context Huberman doesn't cover in this clip. The data suggests cold can be beneficial for hormonal regulation generally — but timing becomes critical. Around the ovulation window, the immune activation that cold triggers can actually work against implantation. Your body's heightened immune state interprets a potential embryo as foreign material.
There's also a 2022 paper on PCOS exploring the relationship between hormonal stimulation and intermittent cold exposure. The takeaway there is that cold's effect on female reproductive hormones isn't uniformly positive — it depends on baseline hormonal state, cycle timing, and whether the exposure is regular or sporadic. Consistent, moderate cold practice looks different in the data than irregular intense exposure.
Both converge on the cortisol story. Regular cold exposure trains your stress response system — specifically the adrenaline-to-dopamine cascade — in a way that reduces chronic cortisol elevation. This is where the fertility benefits for women are most defensible. Chronic cortisol disrupts the hypothalamic-pituitary-gonadal axis. It suppresses LH and FSH. It creates the conditions where cycles become irregular and conception becomes harder. Cold, used consistently, blunts that chronic elevation by front-loading the stress response in a controlled, predictable way.
The disagreement in the literature is more about degree and timing than mechanism. Huberman is broadly optimistic. The European reproductive research is more cautious about the ovulatory window. Both can be true simultaneously.
For men: short, regular cold immersion makes biological sense if heat is a factor — and for most men in sedentary, clothed environments, it probably is. One to three minutes, most days, morning timing. Not for direct testosterone effects. For the thermal environment your reproductive biology actually requires.
For women who are actively trying to conceive: consider pausing or reducing cold exposure during the three to four days around ovulation. Every other week of your cycle, cold practice is likely supportive. During that critical window, err toward warmth and rest.
What strikes me most here is how fertility becomes a proxy for overall stress system health. The populations who struggle most with unexplained infertility are often the same populations carrying the highest chronic stress loads — high cortisol, disrupted sleep, metabolic dysregulation. Cold exposure addresses all three upstream. Not by targeting the reproductive system directly, but by recalibrating the hormonal environment the reproductive system lives inside.
This is the deeper pattern across everything in the knowledge base: cold and heat don't fix specific problems. They restore the conditions under which your body fixes itself. Fertility isn't an isolated system. It's a downstream reflection of how well everything else is working. Start there.