Rapamycin, a compound initially discovered as an antifungal agent, has garnered considerable interest in longevity research due to its ability to inhibit mTOR, a protein that plays a critical role in cellular growth and aging. Studies in animal models have demonstrated rapamycin’s potential to extend lifespan and improve healthspan. However, translating these findings into human applications has proven complex, as substantial risks often accompany the benefits.
Bryan Johnson is an internet personality who has made a name for himself by talking about his sometimes extravagant n=1 biohacking attempts to reverse aging. Recently, Johnson announced a reversal on his position on rapamycin: He thinks it might be making him age worse.
Johnson tested various rapamycin dosing protocols to explore its anti-aging potential while minimizing adverse effects. These protocols included weekly doses of 5, 6, and 10 milligrams, biweekly doses of 13 milligrams, and an alternating weekly schedule of 6 and 13 milligrams.
Although data from preclinical trials were promising, Johnson concluded that the long-term use of rapamycin in humans does not outweigh its drawbacks. Side effects, including intermittent skin and soft tissue infections, impaired lipid metabolism, elevated glucose levels, and increased resting heart rate, persisted regardless of dosage adjustments. After ruling out other potential causes, he attributed these issues to rapamycin and ultimately decided to discontinue its use.
Other research supports his observations, demonstrating that chronic rapamycin use can impair lipid profiles, induce insulin resistance, and contribute to glucose intolerance and pancreatic beta-cell toxicity. While anecdotal evidence suggests that rapamycin may slow tumor growth, its suppression of natural killer cells raises concerns about impaired immune surveillance and potentially increased cancer risk over time.
Further complicating the picture, a recent pre-print study presented new findings about rapamycin’s effects on aging. The study assessed the effects of rapamycin across 16 epigenetic aging clocks and found that it accelerated aging markers in humans. This analysis is noteworthy because most assessments have relied on only one or two aging clocks, raising concerns about the reliability of the findings.
As Johnson notes, longevity research is a rapidly evolving field that requires continuous scrutiny of emerging studies and biomarkers. For now, his experience underscores the importance of balancing potential benefits against risks when exploring experimental compounds like rapamycin. Learn more about rapamycin in our overview article.
