More on (red) wine polyphenols and gut microbiota

There seems to be an increasing scientific interest in wine polyphenols and their influence on the gut microbiota.

The authors of this publication look at the current evidence regarding the relationship between red wine polyphenols and their influence on the gut microbiota.

Various red wine polyphenols including flavonoids (i.e. anthocyanins), non-flavonoids (stilbenes), catechins, etc. are supposed to exhibit positive health effects by reducing the oxidative stress in the body and promoting beneficial gut bacteria. Once digested, relatively small amounts of the wine polyphenols are absorbed by the small intestine (5-10%). These reach the colon as the central place of activity and metabolism by the gut microbiota.

However, the differences between individuals play an important role in the bioavailability (the proportion of the polyphenols that enter the circulation and have an effect in the body) of polyphenols and their respective metabolites in the gut microbiota. The gut microbiota is relatively consistent through the adult life; however, it can be affected by changes in the diet and by antibiotic medication. It plays a critical role for the onset and development of several metabolic and inflammatory conditions/diseases.

The authors state there is no doubt that changes of the gut microbiota and the possible beneficial health outcomes depend on dietary intake; and understanding the benefits of red wine polyphenols on gut microbiota remains challenging and controversial. Some of these factors include the diversity of wines consumed and the variation in their polyphenolic content which is influenced by a variety of factors. Even with excessive doses, evidence of cardio-metabolic effects/benefits are inconclusive. Therefore, it is still unknown whether moderate to high intake levels will have beneficial health effects without negative implications on the gut barrier integrity and the gut microbiota.

The researchers conclude that the influence of red wine polyphenols on gut microbiota is becoming widely recognised, however, further research of low to moderate intake of those wine polyphenols over extended periods of time is necessary to elucidate the impact of various factors. They caution that wine consumption should always be studied in the context of overall dietary habits to account for residual confounding and bias. Results from large clinical studies are needed to establish a cause and effect relationship between red wine polyphenols and the gut microbiota.

Naumovski, N. et al, Untangling the two-way relationship between red wine polyphenols and gut microbiota, Gastroenterology (2019), https://doi.org/10.1053/j.gastro.2019.10.015