Spermidine

What the evidence says

Spermidine is a polyamine present in food and produced within the body. It can promote autophagy in experimental systems, and animal or observational findings made it a proposed caloric-restriction mimetic, but these mechanisms do not establish a useful anti-aging dose in humans.^[1]

A three-month randomized pilot in 30 older adults with subjective cognitive decline reported a moderate memory signal from a wheat-germ extract. The follow-up SmartAge trial randomized 100 adults for 12 months and found no significant improvement in its primary memory outcome or secondary biomarkers versus placebo.^[2][3]

Oral pharmacology is also unresolved. A 12-person crossover study using 15 mg daily for five days did not raise plasma spermidine, while a company-funded 28-day trial of purified 40 mg daily in 37 older men found minimal circulating changes. A supplement dose therefore cannot be assumed to create the cellular exposure seen in laboratory experiments.^[4][5]

A 2026 pilot in 40 older adults found improved immune and vaccine-response markers in selected vaccine nonresponders after 13 weeks, but this is a small exploratory result rather than proof of fewer infections, slower immune aging, or longer life. No randomized human study has demonstrated lifespan extension or a validated reduction in biological age.^[6][1]

Short trials reported balanced adverse events or good tolerability, but they are too small and brief to define uncommon toxicity, cancer-related concerns, interactions, or safety in pregnancy and chronic disease. Food-derived extracts and purified spermidine salts also should not be treated as identical interventions.^[3][5]