Commentary: bioavailability of flavonoids and polyphenols: call to arms.

Dietary polyphenols (Fig. 1) are a main source of antioxidants for humans1. These polyphenols have a variety of biological activities, ranging from anti-ageing, anticancer, to lowering of blood cholesterol level and improving bone strength1–6. Millions of women also take a subclass of polyphenols called phytoestrogens to relieve symptoms associated with menopause7, 8.