Bryan Johnson has tracked his erections, injected his son’s plasma, monitored his girlfriend’s vaginal microbiome, and eaten the same 2,000-calorie meal every day for years. His latest experiment involves ice packs on his testicles, and now half a million people on Reddit are following suit.
Johnson, the billionaire biohacker behind Project Blueprint, claims that 27 daily sauna sessions with an ice pack strapped to his groin produced a 57% increase in total motile sperm count, a 26% jump in concentration, and improvements across morphology and motility. He posted the numbers to X himself, describing the ice protocol as the single most important variable in his sauna routine. He also says he has four times the average sperm count. These are his own figures, from his own experiments, on himself.
The Reddit biohacking community, which draws over 555,000 weekly visitors, has been running its own informal trials. “My protocol is super simple: ice pack over my boxers, 15 minutes per session, three to four times a day,” one user wrote, per Metro. After a year, he reported his highest-ever testosterone levels on a blood test, more powerful ejaculations, and a sex drive that was, in his words, “through the roof.”
Is There Any Science Behind Icing Your Balls?
The underlying logic isn’t completely without merit. Testicles hang outside the body for a reason—sperm production requires a temperature a couple of degrees below core body temperature, around 95°F. One study found sperm concentration dropped 40% for every degree of increase in scrotal temperature. A 2005 study on men with fertility issues found that nocturnal scrotal cooling over 8 to 12 weeks produced significant increases in sperm concentration and total count. A 2013 systematic review also found scrotal cooling beneficial for male fertility — with an important caveat. Those studies used mild, wearable cooling devices worn overnight, not ice packs applied multiple times a day.
The science is more complicated than Johnson’s personal data suggests. Dr. Ramy Abou Ghayda, urologist and chief medical officer at Legacy, told the fertility platform that while heat exposure does real damage to sperm, actively icing to go below optimal temperature is a different claim. Urologist Lye Diwa was more direct, telling VICE that “although there are small studies that would attest to cold temperature and improvement in sperm quality, there are no large clinical trials that would advise icing as a means to improve sperm count.” One study found the opposite effect, showing that cold exposure actually decreased testosterone in young men.
Martin Gross, an associate professor of surgery at Dartmouth, told Verywell Health there’s no evidence that icing improves testosterone or sperm production, and that sleep, exercise, weight management, and cutting back on alcohol are considerably more effective.
Male testosterone levels have dropped 54% between 1972 and 2019, driven by environmental factors including heat exposure and microplastics—the latter of which Johnson has also been campaigning against loudly. The anxiety pushing men toward ice packs is understandable. Practical, though? That’s up for debate.
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