Quercetin bioavailability studies in humans show wide variability (1–50%) depending on the form, food matrix, gut microbiome composition, and co-consumed fats. The aglycone form (in most supplements) has the lowest bioavailability; quercetin-3-glucoside from onions achieves ~24%; phytosome form achieves 5–50x greater AUC than aglycone in direct crossover comparisons.

Is quercetin from food better than supplements?

Quercetin from whole foods (particularly onions — quercetin-3-glucoside form) has better bioavailability than standard supplement aglycone. However, food provides lower total doses than supplements. For therapeutic purposes, phytosome supplements provide the best combination of dose and bioavailability.

Does refrigeration affect quercetin supplement stability?

Quercetin is stable at room temperature in dry form. Light exposure degrades quercetin over time. Store in a dark, cool location; refrigeration is unnecessary but not harmful.