Supplement analysis backed by scientific evidence · PT

← All supplements
Limited evidenceLongevity & antioxidants

Spermidine

An autophagy-inducing polyamine backed by strong epidemiology and animal data — and by a well-run randomized trial in older adults with memory complaints that found no cognitive benefit. The observational signal is likely confounded by diet quality.

What the science says

  • Memory and cognition in older adults Limited evidence

    The best test to date, a 12-month randomized double-blind trial in 100 older adults with subjective cognitive decline (JAMA Network Open 2022), found no significant difference in memory performance between spermidine-rich wheat germ extract (~0.9 mg/day) and placebo on the primary outcome or on any biomarker. An earlier 3-month pilot suggested a benefit; the larger, longer trial did not confirm it.

  • Mortality and cardiovascular outcomes Limited evidence

    In the prospective Bruneck cohort (829 participants, 20-year follow-up), the highest tertile of dietary spermidine intake was associated with a mortality hazard ratio of about 0.42 versus the lowest, an effect the authors compared to being 5.7 years younger. But spermidine-rich foods are whole grains, legumes, mushrooms and aged cheese — this is observational data on a marker of a good diet, and it cannot establish that the molecule itself is responsible.

  • Autophagy induction Limited evidence

    Spermidine induces autophagy in yeast, flies, worms and mice via EP300 inhibition and extends lifespan in each of those models. In humans, oral supplementation raises plasma spermidine only modestly because gut bacteria and the polyamine pool buffer intake, and no trial has demonstrated increased autophagic flux in human tissue.

  • Hair and skin Limited evidence

    Claims about hair growth trace to one small trial of a spermidine-based nutritional supplement on hair follicle anagen phase. It was small, industry-run and not independently replicated.

Dosage & safety

Studied doseTrials have used spermidine-rich wheat germ extract delivering roughly 0.9-6 mg spermidine per day for 3-12 months; commercial products typically supply 1-10 mg/day. Dietary intake ranges from about 7-25 mg/day depending on the diet, meaning food (wheat germ, natto, aged cheese, mushrooms, peas) often supplies more than a supplement does. There is no established effective dose because no dose has produced a clinical benefit in a well-powered trial.
SafetyWell tolerated in trials up to 12 months at the doses tested; mild GI symptoms are the main complaint. Wheat germ-derived products contain gluten and are unsuitable in celiac disease. The main theoretical concern is that polyamines are required for cell proliferation and are elevated in many tumours — polyamine-restricted diets are used experimentally in cancer — so people with an active malignancy should not supplement without oncologist input. Avoid in pregnancy and lactation for lack of data. Aged cheese and other high-polyamine foods can also be high in tyramine, which matters if you take an MAO inhibitor.

Scientific references

Where to buy

Humanx, Spermidine+, Wheat Germ Extract Blend, 60 Capsules

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in Longevity & antioxidants