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We ask a lot of questions about our diet. Whatās the right way to treat a chronic illness? Fight off a virus, lose weight? The problem is, we get a lot of different answers. Well, Iām here to helpāwelcome to the Nutrition Facts Podcast. Iām your host, Dr Michael Greger.
It sounds like science fiction: bacteria in a vial of dirt taken from a mysterious island create a compound that prolongs lifeāand not just in the traditional medical sense. Thanks to advances in modern medicine, weāre living longer lives, but mostly by lengthening the morbidity phaseāweāre living longer but sicker lives. Traditional medical approaches tend just to increase the number of old people in bad health. Ideally, weād extend lifespan by slowing aging so we delay the onset of deterioration instead of merely extending the period of deterioration.
Thatās exactly what this new compoundārapamycināappeared to do. Named for its birthplace, the mystical Easter Island (Rapa Nui), rapamycin inhibits an enzyme now known as mTOR (āmechanistic target of rapamycinā), a master determinant of lifespan and aging. mTOR is the major regulator of growth in animals: it drives increases in cell size and number. But its action has been likened to the engine of a speeding car with no brakes. Aging becomes a car hurtling into the low-speed zone of adulthood, damaging itself because it canāt slow down.
Why donāt organisms have brakes? In the wild, few animals live long enough to experience aging; most die before adulthood. Throughout most of human history the same was trueā17th-century Londoners rarely made it to 16. Evolution therefore selects for rapid growth and early reproduction; once genes are passed on, the growth engine (mTOR) keeps roaring even though itās now harmful. In childhood, mTOR is an engine of growth; in adulthood, it becomes an engine of agingāan example of antagonistic pleiotropy, where a gene helpful when weāre young becomes harmful when weāre old.
Unconstrained mTOR-fueled growth has downsides: it revs up construction pathways that can feed cancerous tumors and, to keep building, actively suppresses autophagyāthe cellās own renovation and cleansing programāaccelerating aging. Conversely, putting the brakes on mTOR decelerates aging; inhibiting mTOR is one of the best-validated longevity interventions we have.
Rapamycin illustrates this. Soil bacteria on Easter Island didnāt evolve the drug to help us; they made it to slow competing soil fungi. Yet dozens of studies show rapamycin extends average and maximum lifespan in mice and every other organism tested so farāeven when started in mid-life. In the landmark 2009 National Institute on Aging study, 600-day-old mice (roughly 60-year-old humans) still lived ~12 % longer after starting rapamycin.
Is it ājustā an anticancer effect? mTOR signaling is hyperactive in up to 80 % of human cancers, and rapamycin is used clinically to prevent organ-transplant rejection. A striking side-effect: in 15 transplant patients with biopsy-proven Kaposiās sarcoma, every skin lesion vanished within three months of starting rapamycin. But animal studies show wider benefits: rapamycin slows or reverses age-related decline in cognition, hearing, arteries, tendons, periodontal bone, and even the aging heartāsometimes with only intermittent or transient dosing (e.g., one dose every five days or a short course in middle age). In the Dog Aging Project, 10 weeks of low-dose rapamycin partially reversed age-related heart dysfunction and owners reported livelier dogs.
Human data remain sparse. Autopsy studies show mTOR activity up to 100-fold higher in Alzheimerās brains, and rapamycin restores memory in Alzheimer mouse models, prompting calls for clinical trialsānone yet exist. Small pilot studies of low-dose rapamycin in older adults found no major side-effects (aside from diarrhea in some) but also no immediate cognitive or physical gains. A larger 2018 trial gave hundreds of adults 65+ a six-week course of very low-dose mTOR inhibition: instead of immune suppression they saw immune rejuvenationābetter flu-vaccine response and fewer infections over the next year.
Still, rapamycin can cause life-threatening infections at higher doses and remains off-patent, limiting commercial incentive for large trials. Until risks are clearer, self-experimentation is discouragedāthough a clinic now caters to people doing just that. Advocates note anti-aging doses are far lower than oncology or transplant regimens and may actually revitalize immunity, especially with transient or intermittent use. But we wonāt know without rigorous studies.
Fortunately, there are ways to tamp down mTOR without drugsāmost notably through dietary strategies Dr Greger covers elsewhere (fasting-mimicking diets, protein moderation, plant-forward eating, etc.).
Weād love to hear your own evidence-based-nutrition success storiesāsubmit them at Share Your Story; we might share them to inspire others.
If you want the graphs, charts, and sources mentioned here, visit the Nutrition Facts Podcast landing page. My latest book, How Not to Age, is out now (check your local library!), and thereās also a mini-book on Ozempic. All my proceeds go to charity. NutritionFacts.org is a nonprofit, ad-free public serviceāno sponsorships, no products, just science in bite-sized videos and articles, offered as a labor of love and a tribute to my grandmother, whose life was saved with evidence-based nutrition.
