Phenolic metabolites as compliance biomarker for polyphenol intake in a randomized controlled human intervention

Clinical trials are needed to confirm the association between polyphenol consumption and lower incidence of chronic diseases observed in epidemiological studies. However, a reliable evaluation of polyphenol intake is complicated. An 8-week randomized controlled trial (78 subjects) was performed using two isoenergetic diets differing only for polyphenol contents. Then, urinary phenolic metabolite profiles were analysed using gas-chromatography with mass detection. Phenolic metabolites detected in 24-h-urine were hydroxylated phenolic acids with C1-C3 side chain in the group consuming polyphenol-rich diet. The intake of polyphenol-rich foods increases the excretion of phenolic metabolites in urine providing a profile, which may serve as compliance biomarker of polyphenol-rich diet