Spermidine triggers autophagy and extends lifespan in animals, but the best human trial found no benefit. We review the evidence, doses and who should be careful.
It isn't proven in people. Spermidine extends lifespan and triggers autophagy (cellular recycling) in yeast, worms, flies and mice, and higher dietary intake is linked to lower mortality in observational studies. But the best human trial, SmartAge (100 adults aged 60 to 90, 12 months), found no effect on memory or biomarkers versus placebo. GenuinePurity Spermidine's 8 mg dose is much higher than anything tested long term.
Autophagy is the process cells use to break down and recycle damaged proteins and other components. In animal studies it tends to decline with age, and spermidine, a compound found in foods such as wheat germ, aged cheese and mushrooms, can switch it on. Whether spermidine supplements meaningfully increase autophagy in people hasn't been established.
Observational studies have linked higher dietary spermidine intake with lower mortality. Studies like these can't show that spermidine caused the difference, because people who eat more spermidine-rich foods may differ in other ways.
The strongest test so far is the SmartAge trial (Schwarz et al., JAMA Network Open, 2022). One hundred adults aged 60 to 90 with subjective memory complaints took 0.9 mg a day of wheat-germ spermidine or placebo for 12 months. There was no difference in memory or in the biomarkers measured.
Current listings show GenuinePurity Spermidine at 8 mg per daily capsule, about nine times the SmartAge dose. There's no efficacy trial at that amount, and its long-term safety at 8 mg a day isn't known. The product is promoted as wheat-germ derived; we couldn't confirm the source or other ingredients on an official label.