Fisetin Supplement

## What is fisetin? Fisetin is a polyphenolic flavonoid present in strawberries (the highest dietary source by concentration), apples, persimmons, onions, and several other plants. Its biological interest comes from preclinical evidence that it functions as a senolytic, a compound that selectively kills senescent (zombie) cells while sparing healthy ones. Senescent cells accumulate with age and drive a chronic inflammatory phenotype known as the senescence-associated secretory phenotype (SASP), which is implicated in age-related disease. The modern senolytic case for fisetin starts with Yousefzadeh 2018 (EBioMedicine), which screened a panel of flavonoids for senolytic activity in cultured mouse and human senescent cells. Fisetin came out as the most potent natural compound tested, clearing senescent cells through Bcl-2 family inhibition and reducing markers of senescence in aged mice. Hickson 2019 (EBioMedicine), a small open-label human trial, then confirmed reduced senescent-cell burden in adipose tissue from older diabetic adults after a single 20 mg/kg/day oral pulse for two days. The Mayo Clinic group has been the dominant academic driver of fisetin's clinical translation. Several human trials are now in progress, including the larger AFFIRM-LITE pilot in older women and ongoing Mayo studies in chronic kidney disease and frailty populations. As of 2026, no completed human RCT has reported on hard outcomes (mortality, frailty progression, cardiovascular events). Legal status: dietary supplement in essentially all major markets, sold as both pure fisetin and as standardized extracts of strawberry, persimmon, or smoke tree (Cotinus coggygria) heartwood. Quality varies enormously across products. ## Mechanism of action Fisetin's senolytic effect appears to act through multiple Bcl-2 family proteins (Bcl-xL, Bcl-w) that senescent cells upregulate to resist apoptosis. By blocking these survival signals, fisetin restores the ability of damaged cells to die on schedule, lowering the SASP-driven inflammatory load. Beyond senolysis, fisetin is a broad polyphenol with effects on Nrf2-mediated antioxidant response, mTOR inhibition at higher concentrations, and direct radical scavenging. The relative contribution of each mechanism to clinical effects in humans is unclear; the senolytic case is the cleanest because it has direct human biomarker data. Pharmacokinetics in humans show low oral bioavailability. The compound is rapidly conjugated and cleared, and plasma half-life is short (1 to 4 hours). The Hickson 2019 protocol used pulsed high doses (20 mg/kg/day for two consecutive days) to overcome bioavailability constraints and exploit a hit-and-run senolytic mechanism: kill the senescent cells in a short window, then let the body recover. ## Evidence base by outcome ### Senescent-cell clearance (human biomarkers) B-tier. Hickson 2019 reported reduced senescent-cell markers in adipose tissue biopsies after the 2-day 20 mg/kg pulse in older diabetic adults (n=10). Multiple ongoing Mayo trials are extending this to other tissues and longer-duration dosing. ### Lifespan in mice B-tier. Yousefzadeh 2018 reported lifespan extension in aged mice with intermittent fisetin dosing (8 to 10% lifespan extension in the published data). Replication across labs is in progress. ### Cognitive function C-tier. Mouse models of accelerated aging show preserved cognitive function with chronic fisetin. Human trials are sparse; one small pilot in healthy older adults reported subjective improvement in memory at 200 to 500 mg/day standardized extracts, but the trial was open-label. ### Inflammation and frailty D-tier. Mechanistic case is plausible (SASP reduction), human trial data still preliminary. ### Cancer The theoretical case is mixed. Fisetin reduces senescent-cell burden, which may lower cancer risk in aged tissues; on the other hand, polyphenols generally have unpredictable interactions with active cancer treatment. Active cancer is a relative contraindication pending clearer data. ## Dosage and administration The two main protocols in current use: - **Pulsed senolytic**: 20 mg/kg/day for two consecutive days, repeated once monthly. This is the Hickson 2019 / Mayo Clinic protocol. For an 80 kg adult, that is roughly 1,600 mg/day for two days. Most users do not approach this dose due to cost and bioavailability. - **Daily low-dose**: 100 to 500 mg/day continuously, typically as a strawberry or smoke tree extract. The mechanistic rationale is weaker (continuous low-dose may not engage the senolytic mechanism the way pulsed doses do), but the safety profile is favorable. With-fat dosing improves bioavailability modestly. Some products combine fisetin with quercetin or piperine to boost absorption; the human trial evidence for these combinations is limited. The Mayo pulsed protocol is the dose with biomarker evidence in humans. Daily low-dose use is empirical. ## Side effects and safety Acute safety has been clean in trials at the 20 mg/kg pulsed dose for 2 days. No serious adverse events were reported in the Hickson 2019 trial. GI upset and mild headache are the most commonly reported effects across trials. Long-term safety data at chronic daily dosing are limited. The compound is present in normal diet, but supplemental concentrated doses have not been characterized over years of use. Drug interactions: fisetin inhibits CYP3A4 and CYP2C9 in vitro at high concentrations, which could theoretically affect metabolism of statins, warfarin, and several psychiatric medications. The clinical relevance at supplemental doses is unclear; users on prescription medications should consult their prescriber. Pregnancy and lactation: insufficient data. Active cancer: relative contraindication pending clearer data on polyphenol-treatment interactions. ## Stack interactions and timing Fisetin is part of the senolytic cluster: rapamycin (Rx, mTOR-driven), urolithin A (mitophagy-driven), spermidine (autophagy-driven), and fisetin (senescent-cell clearance) target overlapping pathways. The combinatorial evidence in humans is essentially absent; pairing is empirical. For pulsed senolytic protocols, isolating fisetin from other senolytics during the 2-day window reduces the chance of compounding side effects and lets the user attribute any subjective response to the intervention. The quercetin + dasatinib protocol (the original Mayo Clinic senolytic) targets a similar mechanism through different molecules; combining quercetin + dasatinib + fisetin in the same pulse is investigational and not validated. ## Practical notes Quality varies widely. The cheapest fisetin products are smoke-tree extracts that may include other flavonoids of unknown content. Strawberry and persimmon extracts are more standardized but more expensive. Third-party-tested products (NSF, USP, ConsumerLab) are the safer choice. Cost is meaningful at the pulsed-protocol dose. A 1,600 mg/day pulse for 2 days, repeated monthly, runs roughly 30 to 80 dollars per month depending on product. For the dietary case, strawberries provide the highest concentration but at quantities (~50 mg fisetin per kg fresh weight) that make food-source supplementation impractical for senolytic effect. Fisetin from food matters for general antioxidant intake; the senolytic dose is a supplement-only target. Expect senolytic effects, if real, to be slow and cumulative. Hickson 2019 reported reduced biomarkers two days after dosing; subjective effects in users are inconsistent. The honest framing for use: fisetin is one of the better-evidenced natural senolytics, but the human case rests on a single biomarker trial and ongoing efficacy studies. Treat it as an early-stage longevity supplement with a strong mechanistic foundation, not a settled clinical recommendation.