Drinking red wine may boost the volume and diversity of the gut microbiome as well as being linked to lower levels of obesity and “bad” cholesterol, finds a twin study* published in the journal Gastroenterology.
A team of researchers from King's College London explored the potential effects of beer, cider, red wine, white wine and spirits on the gut microbiome and subsequent health in 916 female twins from the UK.
Food frequency questionnaires were used to find out average glasses (two units of alcohol each) were drunk every month.
The results were compared with two other groups from the Flemish Gut Flora Project (1104) and the American Gut Project (904).
They found that the gut microbiome of red wine drinkers was more diverse than that of people who didn’t drink red wine, even those who drank rarely or only occasionally, after taking account of potentially influential factors, such as age, weight, diet and socioeconomic status.
The difference wasn’t observed for white wine, beer, or spirits consumption, and the same result was observed in all three groups.
First study author, Dr Caroline Le Roy, said: "While we have long known of the unexplained benefits of red wine on heart health, this study shows that moderate red wine consumption is associated with greater diversity and a healthier gut microbiota which partly explains its long debated beneficial effects on health."
A gut microbiome with a higher number of different bacterial species is regarded as a marker of gut health.
The authors believe the main reason for the association is due to the many polyphenols found in red wine. Among their beneficial properties is the fuel they provide for gut microbes.
Lead author Professor Tim Spector, added: "This is one of the largest ever studies to explore the effects of red wine in the guts of nearly three thousand people in three different countries and provides insights that the high levels of polyphenols in the grape skin could be responsible for much of the controversial health benefits when used in moderation."
The study also found that red wine consumption was associated with lower levels of obesity and “bad” cholesterol which was in part due to the gut microbiota.
"Although we observed an association between red wine consumption and the gut microbiota diversity, drinking red wine occasionally, such as once every two weeks, seems to be enough to observe an effect.
“If you must choose one alcoholic drink today, red wine is the one to pick as it seems to potentially exert a beneficial effect on you and your gut microbes, which in turn may also help weight and risk of heart disease. However, it is still advised to consume alcohol in moderation," added Dr Le Roy.
Dr Sadie Boniface, research coordinator, The Institute of Alcohol Studies, commented: “This one study is not definitive but found associations between red wine consumption and increased gut microbiota diversity thought to be important for health.
“However, no doctor would recommend drinking on medical grounds, as any potential benefits of red wine polyphenols should be considered alongside alcohol’s links to over 200 health conditions, including heart disease and cancers as identified in the chief medical officer’s guidelines review. Polyphenols are also available from in a range of other foods besides red wine.”
Kim Barrett, distinguished professor of medicine, UC San Diego, added: “Like the vast majority of microbiota studies in humans, the findings reflect associations rather than causality, particularly with regard to the implication that the microbiota mediates the effect of red wine consumption on ‘bad’ cholesterol and obesity.
“As the authors themselves note, sorting out any causal effects would require a randomised trial, which probably will never occur. On the other hand, the fact that many of their findings could be replicated across three different cohorts of subjects in different countries adds great weight to their conclusions, and the use of twin pairs is also very helpful to remove many confounding factors.”
Le Roy, Wells PM, Si J, et al. Red wine consumption is associated with increased gut microbiota α-diversity in three independent cohorts. Gastroenterology 2019, DOI: 10.1053/j.gastro.2019.08.024