Bryan Johnson’s latest biohack is nuts.
Over the years, the tech mogul has turned his quest for eternal life into a public spectacle, subjecting himself to extreme anti-aging experiments and sharing how they affect even the most intimate parts of his body in startling detail.
This week, the 48-year-old raised eyebrows by boasting about a new feat involving his testicles, which he said “may be a world-first breakthrough in fertility research.”
“This should not be possible,” Johnson wrote in a May 7 post on X.
The breakthrough? According to Johnson, he went from having 165 microplastic particles per milliliter in his semen to zero in just 18 months.
“I am the first human ever to show a complete reduction to zero,” the millionaire biohacker wrote.
He also shared the exact protocol he used to do it.
Microplastics are ubiquitous, found in everything from toys and cosmetics to cleaning products and clothing. They’re in the air we breathe, the food we eat and the water we drink and swim in.
Over time, they’ve made their way into the body, too.
The tiny fragments, which break off from larger plastics, have been detected in nearly all organs and tissues, including testicles and sperm.
Research suggests microplastics in the male reproductive system may be alarmingly common, with several studies finding them in every semen or testicular sample tested.
Scientists are still exploring exactly what the particles do to the body, but mounting evidence suggests they may harm digestive, respiratory, cardiovascular and reproductive health.
Some studies have linked them to lower sperm concentration, more abnormally shaped sperm and 1 — raising concerns about their potential effects on fertility.
Johnson said the issue matters even for men who aren’t trying to have children, calling sperm count one of the “cleanest biomarkers of overall health.”
“Inside the body, plastic causes a kind of cellular rust,” he explained. “It triggers inflammation in the testicles, kills the cells that make sperm and drops testosterone.”
Determined to keep his privates plastic-free, Johnson launched a three-part effort to clear the particles from his body.
And while he can’t prove anything definitively, the results are hard to ignore.
The concentration of microplastics in Johnson’s semen reportedly dropped from 165 particles per milliliter in November 2024 to 20 particles per milliliter by July 2025. Last month, he said, that number hit zero.
“I did all three interventions at the same time. I cannot say which one did the most work,” Johnson wrote. “What I can say is this: going from 165 to zero in 18 months is possible.”
The first thing Johnson added to his routine was time in a dry sauna, a high-heat room with low humidity.
The longevity fanatic previously gave fans a peek at his regimen, revealing last year that he spends 20 minutes a day in a sauna set to 200 degrees Fahrenheit, while applying an ice pack to his groin area to “safeguard testicular and sperm health.”
“My toxin blood panel confirms sauna clears plastic related chemicals: BPA, phthalates, PFAS, flame retardants, pesticides,” he wrote on X this week. “The plastic particles themselves are too big to sweat out directly.”
However, Johnson claimed heat may activate other clearance routes, including bile flow through the liver, the gut barrier and the body’s cellular cleanup systems.
“Humans have almost no enzymes that can break plastic apart, so the body has to physically push it out,” he wrote.
While saunas are known to induce sweating and may help release trace toxins, some studies suggest that high heat exposure can negatively affect sperm quality and production.
It’s unclear whether any research has examined sauna use combined with cooling the groin area.
In reducing his microplastic count, Johnson also said he uses a reverse osmosis water filter.
The purification system uses a semipermeable membrane that filters out heavy metals, “forever chemicals” and most other contaminants, while letting clean water pass through.
Research suggests both tap and bottled water are major sources of microplastic exposure, with one study finding an average of 325 plastic particles per liter of bottled water, compared with 5.5 particles per liter of tap water.
“I filter everything I drink.” Johnson wrote.
Finally, Johnson has been cutting plastic out of his daily life wherever possible — tossing items like plastic cutting boards, food containers, non-stick pans, tea bags, water bottles and synthetic clothing, all of which can shed microplastics over time.
“As hard as I try, I’m always finding new plastic things in my life,” he acknowledged. “This can be all-consuming thing so try to just knock out the big ones.”
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