Fisetin
The strawberry flavonoid being tested as a senolytic.
Senescent cells — damaged cells that stop dividing but refuse to die — accumulate with age and secrete inflammatory signals that harm surrounding tissue. In a 2018 screen of ten flavonoids, fisetin was the most potent at clearing them, and it extended both median and maximum lifespan in mice even when started late in life. Human senolytic trials are underway but not yet published, so fisetin is a promising lead, not a proven therapy. Its richest food source, by a wide margin, is strawberries.
How Fisetin affects aging
Cellular senescence starts as a safety mechanism: a cell with serious DNA damage locks itself out of dividing, which prevents cancer. The problem is what happens next. Senescent cells resist the normal death signals, linger for years, and pump out a cocktail of inflammatory molecules — the senescence-associated secretory phenotype, or SASP — that degrades surrounding tissue and recruits more cells into senescence. Their accumulation is a core hallmark of aging, and in mice, genetically clearing them delays multiple age-related diseases at once.
Senolytics are compounds that push senescent cells over the edge while sparing healthy ones, typically by blocking the pro-survival pathways senescent cells depend on. In the 2018 EBioMedicine screen, fisetin outperformed nine other flavonoids at this job. Fed to aged mice — the equivalent of starting treatment in a 75-year-old — it reduced senescence markers across tissues, restored tissue homeostasis, reduced age-related pathology, and extended both median and maximum lifespan. It also reduced senescence markers in human fat tissue treated in the lab.
Now the honest part: no published randomized trial has yet shown that fisetin clears senescent cells in living humans. Clinical trials at institutions including the Mayo Clinic are testing intermittent high-dose fisetin in older adults, but results are pending. Fisetin is also poorly absorbed and rapidly metabolized, so whether oral dosing reaches senolytic concentrations in human tissue is an open question. Strong mouse data, plausible mechanism, unproven in people — that is the current state, stated plainly.
Dosage
RDA: No official RDA established. Typical dietary intake is tiny — well under 1mg per day for most people — because few common foods contain meaningful amounts.
Optimal for longevity: Unknown. Mouse studies used brief, high doses that would translate to grams in humans, and ongoing clinical trials use intermittent high-dose protocols under supervision. No evidence-based human dose exists yet; researchers who eat for fisetin simply eat strawberries regularly.
Food first has a catch here: a cup of strawberries delivers roughly 24mg of fisetin — pleasant and worthwhile, but orders of magnitude below the doses used in animal senolytic studies. Eat berries for their overall polyphenol package and their solid epidemiology; do not expect food-level fisetin to clear senescent cells.
Supplements typically provide 100-500mg. Clinical trials use a different logic: brief, high-dose 'hit-and-run' courses on a few consecutive days, on the theory that killing senescent cells does not require continuous exposure. Because human efficacy and long-term safety are unestablished, high-dose self-experimentation is premature — if you try it anyway, involve your physician, especially alongside any medication.
Deficiency signs
Not a deficiency nutrient; most diets contain almost none unless berries are eaten regularly
- No deficiency syndrome — fisetin is not an essential nutrient
- Diets without strawberries or apples provide almost none
- Low intake simply means missing a candidate senolytic, not a clinical deficit
- Berry-poor diets also tend to be low in related flavonoids with better-established benefits
Top food sources
What the research shows
Screening ten flavonoids, fisetin was the most potent senolytic. In progeroid and naturally aged mice it reduced senescence markers in multiple tissues, restored tissue homeostasis, reduced age-related pathology, and extended median and maximum lifespan — even when started in old age. It also reduced senescence markers in human adipose tissue ex vivo. Animal and lab evidence only.
The paper that launched the field: transcriptome analysis revealed that senescent cells depend on specific pro-survival pathways, and drugging those pathways selectively eliminated them. In aged mice, senolytic treatment improved cardiac function and extended healthspan — the framework within which fisetin was later identified.
Frequently asked questions
Can I get senolytic doses of fisetin from food?
No. The mouse studies used doses that would translate to grams per day in humans; a cup of strawberries provides about 24mg. Eat strawberries because berries are among the best-supported longevity foods overall — not as a senolytic protocol.
Has fisetin been proven to work in humans?
Not yet. The lifespan and senescent-cell-clearance results come from mice and lab-treated human tissue. Randomized human trials are running, but as of now no published trial shows fisetin clears senescent cells in people.
Why do trials dose fisetin intermittently instead of daily?
Senolytics aim to kill senescent cells, not to maintain a steady blood level — once a cell is cleared, it stays cleared for a while. Hence brief high-dose courses ('hit and run') separated by weeks or months, which may also limit side-effect exposure.
Is taking a daily low-dose fisetin capsule useful?
Unknown, and the senolytic logic argues against it — low continuous doses were not what worked in animals. Daily fisetin has antioxidant and anti-inflammatory activity in lab studies, but so do many cheaper, better-studied polyphenols from food.
Is fisetin safe?
At dietary levels, certainly. Supplement doses have been used in short trials without major safety signals, but long-term high-dose human data do not exist, and flavonoids at gram doses can interact with medications. Clear it with your doctor before high-dose use.
Track your fisetin intake
Biohack logs fisetin alongside 22 other longevity nutrients in every meal.