Spermidine
/ Endogenous polyamine; autophagy inducer (small molecule)ALIAS · Spermidine · N1-(3-aminopropyl)butane-1,4-diamine
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Tier 3. The strongest geroscience evidence is murine: Eisenberg and colleagues (2016) reported dietary spermidine supplementation extended lifespan in mice and reduced cardiac hypertrophy. Human evidence is limited to small cohort and trial data — most prominently the SmartAge trial of spermidine in older adults with subjective cognitive decline (Schwarz and colleagues 2018). Sold widely as a supplement (wheat germ extract is the predominant commercial source) under the US DSHEA framework; not FDA-approved for any indication.
Spermidine is an endogenous triamine (1,4-diaminobutane with an aminopropyl substituent on N1) and one of three principal mammalian polyamines alongside putrescine and spermine. Spermidine is the unique substrate for hypusine modification of eukaryotic translation initiation factor 5A (eIF5A), an essential post-translational modification required for translation of polyproline-rich proteins.
The geroscience interest derives primarily from spermidine's capacity to induce macroautophagy through inhibition of cytoplasmic histone acetyltransferases (notably EP300), shifting the cellular acetylation balance toward histone deacetylation and de-repressing autophagy gene transcription. Endogenous tissue spermidine declines with age in multiple mammalian models; supplementation is hypothesised to restore polyamine pools and re-establish autophagic flux. Dietary sources include wheat germ, fermented soybean products, and aged cheese; commercial supplement formulations are predominantly wheat germ-derived spermidine concentrates.
Tier 3. Eisenberg and colleagues (2016) reported lifelong dietary spermidine supplementation extended median and maximum lifespan in mice, with reductions in cardiac hypertrophy and improvements in arterial function — the foundational mammalian lifespan study. The SmartAge trial (Schwarz and colleagues 2018) randomised 30 older adults with subjective cognitive decline to spermidine-rich wheat germ extract or placebo for three months and reported modest improvements in memory performance.
Generally well-tolerated in published trial doses. Reported adverse events at the trial doses studied (1-2 mg spermidine equivalent daily from wheat germ extract) include mild gastrointestinal upset. Food-source spermidine intake in normal Western diets is typically several-fold higher than supplement doses without identified safety issues. Long-term safety of concentrated supplement formulations beyond the durations studied has not been characterised.
Regulatory status
- FDA status:
- Not FDA-approved
Long-term outcome data are sparse. The SmartAge cognitive results are from a small short-duration trial; the murine lifespan finding is the most robust geroscience datapoint but does not directly demonstrate human longevity benefit. The supplement category includes products of variable spermidine content and concentration; vendor product specifications and analytical certificates of analysis vary substantially. Some interest has focused on whether plasma or tissue spermidine is the relevant pharmacodynamic readout, and whether wheat germ extract delivers meaningful spermidine to target tissues — questions not yet resolved by the current clinical trial literature.