Spermidine

Spermidine is the premier autophagy-inducing longevity compound, validated by the 12-month SmartAge double-blind RCT (PMC9136623) testing 0.9mg/day in older adults with subjective cognitive decline, which confirmed safety and tolerability with no significant adverse events. This naturally occurring polyamine, concentrated in wheat germ and aged cheese at levels up to 800 nmol/g, induces autophagy by inhibiting acetyltransferases that suppress the autophagy regulatory network and stabilizing LC3 for autophagosome formation. Its mechanism is distinct from caloric restriction and mTOR inhibition, meaning it complements metformin, rapamycin, or AKG in a stack without overlap—unlike Fisetin, which targets senescent cells via PI3K/Akt/mTOR inhibition. Human epidemiological data correlating higher dietary spermidine intake with 10% lower all-cause mortality supports higher-dose protocols (5–15mg/day of purified spermidine), as the SmartAge dose may be subtherapeutic for maximal autophagy induction. Spermidine levels decline with age, mirroring taurine's depletion-and-restoration rationale. The wheat germ source provides a well-tolerated delivery vehicle, and supplementation costs are modest at $20–50/month for quality extracts.