Urinary flavonoids and phenolic acids as biomarkers of intake for polyphenol-rich foods.

Estimation of dietary intake of polyphenols is difficult, due to limited availability of food composition data and bias inherent to dietary assessment methods. The aim of the present study was to evaluate the associations between the intake of polyphenol-rich foods and the urinary excretion of several phenolic compounds and therefore explore whether these phenolic compounds could be used as a biomarker of intake. Fifty-three participants of the SU.VI.MAX study (a randomised primary-prevention trial evaluating the effect of daily antioxidant supplementation on chronic diseases) collected a 24 h urine and a spot urine sample and filled a dietary record during a 2 d period. Thirteen polyphenols and metabolites, chlorogenic acid, caffeic acid, m-coumaric acid, gallic acid, 4-O-methylgallic acid, quercetin, isorhamnetin, kaempferol, hesperetin, naringenin, phloretin, enterolactone and enterodiol, were measured using HPLC-electrospray ionisation-MS-MS. In spot samples apple consumption was positively correlated to phloretin, grapefruit consumption to naringenin, orange to hesperetin, citrus fruit consumption to both naringenin and hesperetin, with r coefficients ranging from 0.31 to 0.57 (P < 0.05). The combination of fruits and/or fruit juices was positively correlated to gallic acid and 4-O-methylgallic acid, isorhamnetin, kaempferol, hesperetin, naringenin and phloretin (r 0.24-0.44, P < 0.05). Coffee consumption was positively correlated to caffeic and chlorogenic acids (r 0.29 and 0.63, P < 0.05 respectively). Black tea and wine consumption were positively correlated with gallic and 4-O-methylgallic acids (r 0.37-0.54, P < 0.001). The present results suggest that several polyphenols measured in a spot urine sample can be used as biomarkers of polyphenol-rich food intake.