Dietary polyphenols for managing cancers: What have we ignored?

Abstract Although the chemoprevention and anti-cancer activities of dietary polyphenols have been evidenced through both in vitro and in vivo studies, most of the human clinical trials were unsuccessful or even harmful. Debates on the beneficial roles of dietary polyphenols in cancer therapy are increasing. Many dietary polyphenols studies are conducted by in vitro experiments, but the nature of these studies does not consider the complexity of metabolic processes that are present in vivo. These can often cause instability in the dietary polyphenols, thereby leading to unsuccessful extrapolation into animal or human studies. Dietary polyphenols often have low bioavailability, which is mainl…