Evaluation of (-)-epicatechin metabolites as recovery biomarker of dietary flavan-3-ol intake.

Data from dietary intervention studies suggest that intake of (-)-epicatechin mediates beneficial vascular effects in humans. However, population-based investigations are required to evaluate associations between habitual intake and health and these studies rely on accurate estimates of intake, which nutritional biomarkers can provide. Here, we evaluate a series of structurally related (-)-epicatechin metabolites (SREM), particularly (-)-epicatechin-3'-glucuronide, (-)-epicatechin-3'-sulfate and 3'-O-methyl-(-)-epicatechin-5-sulfate (SREM), as flavan-3-ol and (-)-epicatechin intake. SREM in urine proved to be a specific indicator of (-)-epicatechin intake, showing also a strong correlation with the amount of (-)-epicatechin ingested (R: 0.86 (95% CI 0.8l; 0.92). The median recovery of (-)-epicatechin as SREM in 24 h urine was 10% (IQR 7-13%) and we found SREM in the majority of participants of EPIC Norfolk (83% of 24,341) with a mean concentration of 2.4 ± 3.2 µmol/L. Our results show that SREM are suitable as biomarker of (-)-epicatechin intake. According to evaluation criteria from IARC and the Institute of Medicine, the results obtained support use of SREM as a recovery biomarker to estimate actual intake of (-)-epicatechin.