Fisetin vs Spermidine
Two preclinical favorites with the same shape of problem. Excellent mouse data on both sides, and human evidence that is either not yet in or, for spermidine, already negative.
Fisetin
The most potent senolytic flavonoid in mice, with lifespan data — but the human senolytic trials are still ongoing, with no published outcomes.
Full Fisetin evidence reviewSpermidine
Autophagy + mouse-lifespan data and a striking diet-mortality association — but the best randomized human trial (memory) was null.
Full Spermidine evidence reviewSide by side
| Fisetin | Spermidine | |
|---|---|---|
| Marketed for | Senolytic, anti-aging | Autophagy, longevity |
| Evidence grade | Preclinical / minimal | Preclinical / minimal |
| Family | Senescence & senolytic | Senescence & senolytic |
| Key human source | Mouse senolytic, EBioMedicine 2018 | Mouse lifespan, Nat Med 2016 |
marks a row where the two differ. Evidence grades come from our evidence matrix, which grades each molecule on the human data for the use it is marketed for.
Our verdict
Both are graded preclinical, and honestly so. Fisetin cleared senescent cells and extended lifespan in old mice, with an independent study finding reduced frailty and better grip strength in aged but not young mice, yet no published human trial tests the senolytic claim and those studies are still ongoing. Spermidine has mouse lifespan and cardiac data tied directly to autophagy plus a striking association between higher dietary intake and lower mortality, but that association is observational and confounded by a generally healthier diet, and the 12-month SmartAge trial in 100 older adults found no effect on its primary memory endpoint. The practical difference is that spermidine has been put to a rigorous randomized test and failed it, while fisetin has not been tested yet; the two have not been compared directly.
Fisetin fits if
Someone betting early on the senolytic hypothesis who understands that every efficacy claim behind it is currently animal data.
Spermidine fits if
Someone who prefers a compound with a clean human safety record at the low doses studied and a real, if confounded, population-level mortality signal.