Spermidine
A natural polyamine and potent autophagy inducer, obtained from foods like wheat germ and natto or as a supplement. It extends lifespan across multiple model organisms and has intriguing human observational data linking dietary intake to lower mortality, but interventional human outcome trials remain small and preliminary.
01 Overview
Spermidine is a ubiquitous polyamine present in all cells and in many foods, whose levels decline with age. It is one of the most reproducible autophagy inducers known, extending lifespan in yeast, worms, flies, and mice, largely through induction of macroautophagy via inhibition of histone acetyltransferases and hypusination of eIF5A.
Human evidence is a mix of promising observational data and small trials. Population studies (e.g. the Bruneck cohort) associate higher dietary spermidine intake with lower all-cause and cardiovascular mortality. Small interventional trials of wheat-germ-derived spermidine suggest a possible benefit for memory in at-risk older adults, though a larger cognition RCT (SmartAge) was essentially null. It is well tolerated.
02 Mechanism
Induces autophagy by inhibiting acetyltransferase EP300 and via hypusination of eIF5A, promoting clearance of damaged organelles and proteins; also has antioxidant and anti-inflammatory effects.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Common | 1–6 mg/day | Oral | Typical supplement dose; often from wheat-germ extract. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Autophagy inductionOne of the most reproducible dietary autophagy inducers across model organisms. | robust | Preclinical | |
| Lower mortality with higher dietary intakeHigher dietary spermidine intake associates with reduced all-cause and cardiovascular mortality in cohort studies. | association only | Observational | |
| Possible cognitive benefit (mixed)Small trials hinted at memory benefit in at-risk elderly, but a larger RCT found no significant effect. | small / inconsistent | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Mild GI effectsWell tolerated in trials; occasional mild digestive complaints. | Mild | Rare | Clinical | |
| Theoretical concern in active cancerPolyamines support cell proliferation, raising a theoretical concern about supplementation during active malignancy. | Moderate | Theoretical | Unconfirmed |