Challenges in providing credible scientific evidence of health benefits of dietary polyphenols

► Credible scientific evidence of health benefits of dietary polyphenols is needed. ► Bioavailability of bioactive compounds must be known. ► Bioavailability includes absorption, distribution, metabolism, and excretion. ► Metabolites must be included in vitro and in vivo studies. ► Physiological concentrations of bioactive compounds must be used.