Fisetin
Fisetin is a plant flavonoid sold as a "senolytic" supplement, meant to clear out worn-out senescent cells. Its reputation rests on one lab's mouse study. A larger, more rigorous mouse lifespan test found no effect, and the first placebo-controlled human trial to post results found no benefit.
There is no good reason to take fisetin to slow aging. No human result supports it, and in the one study that measured biological-age markers, adding fisetin to dasatinib plus quercetin did not stop one key clock rising.
What it is
Fisetin is a flavonoid, one of the polyphenol compounds plants make, like quercetin. It is marketed as a senolytic: a compound that selectively kills senescent cells. These are damaged cells that stop dividing but do not die, and they leak inflammatory signals into the tissue around them as they accumulate with age (see Cellular senescence).
Like the other flavonoids sold on this story, it is poorly absorbed. These compounds are water-insoluble, unstable in the gut and rapidly broken down by the liver, so swallowing unformulated powder produces negligible blood levels.[1]
One striking mouse result that didn't replicate
The case for fisetin comes from a single laboratory's 2018 study. Fisetin reduced senescence in some cell types in mouse fat and in samples of human fat tissue treated in the lab. Given to mice late in life, it extended both median and maximum lifespan.[2] The "human" part of that result means fat tissue in a dish, not people taking fisetin.
The US National Institute on Aging's Interventions Testing Program then tested it. The programme runs lifespan tests at three sites in genetically mixed mice. Fisetin did not extend lifespan in either sex.[3]
What human trials show so far
- Knee osteoarthritis: no benefit. In 74 people with knee osteoarthritis, two short courses of high-dose fisetin (about 20 mg per kilogram of body weight for two days, repeated a month later) caused no more side effects than placebo, which was the trial's main goal. But fisetin also did no better than placebo on knee pain over 12 weeks, or on walking tests, cartilage on magnetic resonance imaging (MRI) scans or blood markers of inflammation over a year, according to results posted on the trial registry.[4]
- Bone: no sign of benefit. In a Mayo Clinic trial in postmenopausal women aged 60 and over, five monthly three-day courses of fisetin over 20 weeks did not lower a blood marker of bone breakdown compared with no treatment; the median change was a 14% rise on fisetin against an 8% fall in the untreated group, and the trial had no placebo and did not formally test fisetin against control.[5]
- Biological-age clocks: the wrong direction. A small study measured DNA-methylation "clocks", lab estimates of biological age, in healthy adults taking the senolytic drug pair dasatinib plus quercetin. A follow-on group then added fisetin. On the clock that drove the original finding, that group's age estimate rose significantly, meaning more apparent aging, not less. It was a different, only partly overlapping group of people, so any comparison with the first group is a comparison across two small studies.[6]
- Still running. Trials are testing fisetin on blood-vessel function in adults aged 65 and over ([7]), low-dose fisetin and inflammation in healthy adults aged 50 and over,[8] and physical function in breast-cancer survivors.[9]
No human result yet supports taking fisetin to slow aging.
Why "natural" doesn't settle it
Senolytics are designed to kill cells, and a tool built to clear sick cells can also stress healthy ones. In healthy adults on dasatinib plus quercetin, the same kind of intervention moved several biological-age clocks the wrong way, and the authors could not show that adding fisetin helped. A supplement-shelf label does not change that logic, and for fisetin there is no human evidence of benefit to set against it.
What to do
- Don't buy fisetin as an anti-aging supplement. The mouse lifespan result failed its independent test, and the human trial with results was null.
- If you want to act on senescent cells, use the levers with human data. Calorie restriction and treating insomnia have randomised-trial support on blood markers; see Cellular senescence.
- If fisetin interests you, the place for it is a trial. Several are recruiting or running.
Further reading
- Yousefzadeh MJ, et al. Fisetin is a senotherapeutic that extends health and lifespan. EBioMedicine 2018.[10]
- Harrison DE, et al. Astaxanthin and meclizine extend lifespan in UM-HET3 male mice; fisetin, SG1002 (hydrogen sulfide donor), dimethyl fumarate, mycophenolic acid, and 4-phenylbutyrate do not significantly affect lifespan in either sex at the doses and schedules used. Geroscience 2024.[11]
- Lee E, Carreras-Gallo N, Lopez L, et al. Exploring the effects of dasatinib, quercetin, and fisetin on DNA methylation clocks: a longitudinal study on senolytic interventions. Aging (Albany NY) 2024.[12]