Quercetin: Bioavailability, Senolytic Research & Food Sources

Quercetin is one of the most abundant flavonoids in the human diet, found in onions, apples, berries, capers, and many other fruits and vegetables. It's gained significant research attention for its anti-inflammatory, antihistamine, and more recently, senolytic properties.

Senolytic Research

Senolytics are compounds that selectively eliminate senescent cells — damaged cells that have stopped dividing but refuse to die, instead secreting inflammatory factors that contribute to aging. The combination of quercetin + dasatinib has shown promising senolytic effects in both animal studies and early human trials, though this is still a developing field.

Bioavailability Challenges

Quercetin's oral bioavailability is relatively low, with absorption estimated at 3-17% depending on the food matrix. Fat co-ingestion improves absorption. Quercetin is extensively metabolized in the gut wall and liver, producing metabolites (like isorhamnetin) that may themselves be bioactive. Some supplement formulations use phytosomal delivery or pair quercetin with bromelain to enhance absorption.

Quercetin is often paired with vitamin C in supplements, as they may have complementary mechanisms in immune support. Quercetin also activates the NRF2 pathway at certain concentrations.

Food Sources

Capers are the single richest source, followed by red onions (especially the outer rings), cranberries, blueberries, apples (with skin), green tea, and buckwheat. Quercetin is more concentrated in the skin and outer layers of fruits and vegetables.

External resources: Linus Pauling Institute — Flavonoids