Does fisetin from strawberries really work as a zombie-cell cleaner?

Fisetin is found in strawberries, but also in apples and onions. In laboratory research it was compared with nine other plant compounds. It turned out to be the most potent 'senolytic': a substance that selectively clears out aged, no-longer-functioning cells (also known as zombie cells). In cell cultures from both mice and humans, the hallmarks of such aged cells dropped measurably. Zombie cells also disappeared from human fat tissue¹. Encouraging, but this is lab and tissue research, not a study in living people.

In mouse studies the results are strikingly consistent. Old mice that received fisetin late in life lived longer on average and reached a higher maximum age. Their tissue health improved and age-related abnormalities decreased¹. Another mouse study showed that an alternating schedule (one week of fisetin, two weeks off, one week of fisetin) reduced arterial stiffness and improved blood vessel function². Age-related changes in blood proteins also reversed after a short-term treatment³. These findings have been replicated across multiple studies, but mouse results do not automatically translate to humans.

In humans, the research is still at a very early stage. Clinical trials are underway in an early phase, but definitive conclusions about safety, dosing and efficacy in humans are not yet available⁴. Small pilot studies with senolytic agents in general, including fisetin, show positive signals: fewer zombie cells, lower inflammation markers and fewer complaints of frailty in older adults⁵. The researchers conducting these trials explicitly state that use outside controlled studies is premature for now.

There are also safety questions. Senolytics as a class have been associated with platelet deficiency. The dosing schedule (continuous or with breaks) also affects both efficacy and side effects⁶. For fisetin in humans, side effects have not yet been sufficiently studied and the optimal dose is unknown. Anyone taking fisetin as a supplement is getting ahead of the current evidence. There is also mouse research into fisetin in serious infections, but those are early animal study data with no clinical evidence in humans⁷.