A man who has tried everything points to the oldest thing

Bryan Johnson has injected bone marrow into his joints. He has had his plasma removed. He has spent 9,500 minutes in a hyperbaric oxygen chamber. He has, by his own description, used his teenage son as a blood boy in a plasma exchange experiment. In the pursuit of not dying — or at least slowing things down considerably — he has tried interventions that sit somewhere between cutting-edge medicine and genuine self-endangerment.

And yet, when asked to name his number-one longevity protocol of 2025, he pointed to something that has been in use for thousands of years: dry sauna.

That is worth paying attention to.

Who is Bryan Johnson?

If you have not encountered Bryan Johnson, he is a tech entrepreneur who sold his payments company to Braintree and then to PayPal, walked away with several hundred million dollars, and chose to spend a significant portion of it attempting to reverse his own biological ageing. He publishes his data publicly, maintains an extremely specific plant-based diet, and sleeps with a focus that most people reserve for competitive sport.

He is, depending on your point of view, either a pioneer doing important early work on human longevity, or a cautionary tale about what happens when a high-functioning person has too much money and too little else occupying his mind. Both readings probably contain some truth. But dismissing him entirely would be a mistake. He has spent millions, partnered with serious scientists, and documented his interventions with more rigour than almost anyone outside of a formal clinical trial.

The extreme end of the spectrum

What sets Johnson apart isn't just the extremity of his interventions — it's the rigour with which he documents them. He tracks hundreds of biomarkers across every protocol, runs controlled measurement periods, and publishes his results publicly. As someone with a background in engineering design, there is something genuinely compelling about that approach: hypothesis, measurement, iteration, applied to the human body with more consistency than most clinical settings manage. Whatever you think of the interventions themselves, the data discipline is interesting.

We are not endorsing any of his more extreme protocols. Some of it sits in genuinely uncertain scientific territory. Some of it is almost certainly unnecessary. And some of it, we suspect, is at least partly driven by the kind of obsessive identity-building that extreme wellness culture can quietly become.

But that context matters when he tells you something simple works.

Why the sauna finding stands out

Sauna is not futuristic. For someone spending millions on longevity interventions, it is not expensive — not compared to plasma exchanges, hyperbaric chambers, or experimental bone marrow injections. It does not require a team of doctors or any particular technology. It has been used in Scandinavia and Finland for centuries, is well-supported in cardiovascular research, and is relatively readily available — compared to stem cell injections, a sauna is accessible to almost anyone.

When someone with access to literally anything points to sauna as a standout intervention, that carries real weight.

Johnson's protocol is specific: dry sauna at 200°F (93°C), very low humidity, 20 minutes, daily, after his morning workout. He reports that his team tracked the results using hundreds of biomarkers across a 30-day period.

What the data showed

The vascular results Johnson published are striking. Key findings post-protocol:

• Central systolic blood pressure: 96 mmHg
• Central pulse pressure: 20 mmHg
• Pulse pressure amplification: 160%
• Subendocardial viability ratio: 227% — a measure of cardiac efficiency
• Traditional blood pressure: 107/75
• Augmentation index: 3% — reflecting very low arterial stiffness
• Vascular function age approximately 10 years younger than his chronological age

He also published findings on microplastics. After the sauna protocol, Johnson reported an 85% reduction in microplastics found in his ejaculate, with a similar reduction measured in his blood. These are self-reported, exploratory findings — not a clinical trial — but they are, at minimum, an interesting prompt for further investigation.

It is worth holding all of this lightly. Johnson's team is rigorous by personal standards, but this remains one data point, from one individual, over one month. Correlation is not causation, and self-experimentation is not peer review.

But if a guy this obsessed with longevity is using sauna regularly — and ranking it above everything else he has tried — that is worth paying attention to.

The complication: heat and fertility

The protocol was not without a significant side effect. Without cooling, sauna appeared to negatively impact Johnson's fertility markers — substantially. He reported a 56% reduction in total motile sperm count, a 30% drop in concentration, a 50% reduction in motility, and a 48% decrease in morphology. These are not small numbers.

His response was to add targeted cooling after sessions — ice the boys — protecting the testes from the sustained heat exposure that sauna creates. He reports that his fertility markers subsequently reached an all-time high, though he acknowledges that his team does not know whether the improvement was caused by sauna, sauna plus ice, or some other factor entirely.

This is an important caveat. For men who care about fertility, the takeaway is not simply that sauna is good. It is that sauna requires some thought about heat management. That nuance matters.

The oldest protocol wins

Bryan Johnson spent millions and tested hundreds of interventions. His number-one longevity protocol of 2025 was something a Finnish farmer has been doing every Friday evening for a thousand years.

That is not a criticism of Johnson. If anything, it is a quiet endorsement of sauna — and of the idea that the most powerful practices are often the ones that require the least explanation.

Bryan, if you are reading this — we are obsessed with a different kind of longevity. I bet I can build a sauna that will outlive you. Hit us up if you are interested.