Podcast episode 83 (in German)
Senolytics off the shelf – fisetin, quercetin and the study that has been running for eight years
September 21, 2026
Fisetin, 500 milligrams per capsule, with the words “cell renewal” on the front. Behind it lies one of the best mouse studies in aging research — and an independent re-examination that found neither the result nor the mechanism again.
What it is about
Senescent cells no longer divide, but they do not die either: they linger, release inflammatory substances and infect healthy neighbors. Senolytics are meant to clear them out selectively, and the principle has been cleanly demonstrated in mice. The episode traces what of this actually reaches the shelf: the 2018 fisetin study that made the field famous, the independent testing program from 2023 that could not confirm it, the human study that has been running for 8.5 years without results, and the question of what a capsule containing quercetin alone is supposed to achieve in this role at all when the substance has never been tested on its own.
Key points
- The 2018 screening paper found fisetin to be the best hit and gave it to mice only from the 20th month of life — late administration, and still a gain in remaining lifespan.
- In the 2023 testing program, mice received 600 ppm fisetin from 20 months, either continuously or on 3 days every 2 weeks: no significant lifespan extension, in either sex and with either regimen.
- The second finding weighs more heavily: senescence markers did not fall, neither in the liver nor in the kidney nor in the brain.
- The human study AFFIRM is testing fisetin in 40 women aged 70 and over; it began in February 2018 and gives November 2026 as the estimated completion date for the primary endpoint.
- The pulse dose tested there, 20 milligrams per kilogram, corresponds to around 1,600 milligrams on a single day for a person weighing 80 kilograms; a standard commercial capsule contains 500.
- In all human studies on senolysis, quercetin was only ever used together with dasatinib, including the 2019 kidney study — never on its own.
- A pharmacological review puts the absorption of quercetin at 0 to more than 50 percent of the dose, with a half-life of under one to just over 2 hours.
Where the data stop
The first fisetin study is not refuted by the testing program: different mouse strains, a different dose, a different route of administration. But a finding that holds up only under the conditions of its first description and disappears in the independent program is unreliable — and for someone holding a pack in their hand, it amounts to the same thing.
In humans, senolysis has so far only been shown with dasatinib, a cancer drug that belongs exclusively in the hands of a physician. The most-cited human study on fisetin has reported nothing after 8.5 years; small studies with frail people are slow, and the pandemic fell right in the middle. Anyone taking blood thinners should clarify high flavonoid doses beforehand, because both substances can affect how the liver breaks these drugs down. Anyone who has just had surgery or has a wound that is healing should wait. The best-supported senolytic available without a prescription remains exercise.
Listen (in German)
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Published on September 21, 2026.
The topic in the database
- Senolytic candidate. The much-cited 2018 mouse study was not confirmed in the independent testing program in 2023.Fisetin
Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-09-19.