A feeding study was carried out in 20 healthy human volunteers and urine samples were collected for 24 h after tea ingestion. Flavan-3-ols–derived molecules were identified and quantified in urine samples by high-performance liquid chromatography with tandem mass spectrometric detection.
Eight relevant metabolites were identified in urine, all modified flavan-3-ols with the exception of unmetabolized gallic acid. The urinary excretion of flavan-3-ols was equal to 7.2 % of the intake with tea. Gallic acid, which was abundant in the RTD tea used in this study, reached a 4.5 % of the drunken amount.
The bioavailability values observed are in agreement with previous reports, although the dosage of polyphenols ingested in this study is remarkably lower. Moreover, the use of a group of 20 volunteers, more than the average number of subjects used for usual human acute-feeding studies involving polyphenols, provides additional credibility to the results. After drinking the RTD ice tea used in this study, the internal compartments are exposed to non-marginal doses of flavanols and flavanol metabolites up to 24 h.