Moderate intake of red wine promotes a significant increase of phenolic metabolites in human faeces

Abstract. With the final aim of ascertaining consistent data about the changes of phenolic metabolites in faeces after a regular wine consumption, the present paper compiles the data from two previous human intervention studies: a) a pilot study (n = 8), that compared the ingestion of de-alcoholised red wine (272 mL/day), red wine (272 mL/day), or gin (100 mL/day) during 20 days, and b) a large trial study (n = 41, 33 cases and 8 controls), that assessed variability among individuals after the intake of red wine (250 mL/day, 28 days). Great coincidence was observed in the main phenolic metabolites identified in the faecal samples from both studies that included benzoic acids, phenols, hippuric acids, phenylacetic acids, phenylpropionic acids, valeric acids, valerolactones and cinnamic acids. However, significant differences (P < 0.05) in the total phenolic content between faecal samples before and after the wine intervention was only observed for the large trial study (358 ± 270 and 625 ± 380 g/g faeces, corresponding to the mean values before and after the intervention, respectively), emphasizing the large variability in the phenolic-metabolizing gut-microbial capacity among individuals. The overall results confirm that consumption of wine enhances phenolic metabolism, which might have physiological relevancy at the gut level