New research suggests that drinking red wine in moderation improves the bacterial diversity in our guts and may protect our overall health.

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A moderate intake of red wine may protect the health of our guts.

Many scientific studies have looked into the alleged benefits of red wine consumption.

From the popular notion that a little bit of red wine is good for the heart, to the less known theory that compounds in red wine may benefit depression or oral health, drinking red wine in moderation seems to have a lot of hidden therapeutic potential.

New research adds to the list of red wine's possible health benefits. An observational study, whose first author is Caroline Le Roy from King's College London in the United Kingdom, examined the gut health of red wine drinkers and compared it with that of people who drank other types of alcohol.

The researchers found a greater diversity of bacterial species in the guts of red wine drinkers compared with those who did not drink red wine. Greater bacterial diversity is a marker of gut health.

Le Roy and colleagues published their findings in the journal Gastroenterology.

Polyphenols may benefit gut health

The scientists examined data from 916 female twins and compared the effects of beer, cider, red wine, white wine, and spirits on the participants' gut microbiotas and overall health.

The team accounted for potential confounders, such as age, weight, diet, and socioeconomic status. After considering all of these factors, the researchers still saw an association between bacterial diversity and red wine consumption.

Red wine drinkers had a higher number of different bacteria in their guts, lower rates of obesity, and lower levels of cholesterol than non-red wine drinkers. The researchers confirmed these findings over three different cohorts based in the U.K., the Netherlands, and the United States.

"While we have long known of the unexplained benefits of red wine on heart health," reports the first author of the research, "this study shows that moderate red wine consumption is associated with greater diversity and a healthier gut microbiota that partly explains its long debated beneficial effects on health."

Professor Tim Spector, from King's College London, also comments on the significance of the findings, suggesting that polyphenols could be responsible for red wine's benefits.

"This is one of the largest ever studies to explore the effects of red wine in the guts of nearly 3,000 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."

Polyphenols are naturally occurring chemicals found in plants. Flavonoids and phenolic acids are types of polyphenols.

Fruits and vegetables are naturally very rich in polyphenols, which are, in turn, full of antioxidants that fight off cell damage. Polyphenols may "fuel" the beneficial microorganisms that live in our guts.

Previous studies have suggested that polyphenols may help protect against a range of cardiometabolic conditions, such as obesity, type 2 diabetes, or heart disease.

Moderation is key

However, the researchers cautioned that theirs was an observational study. This means that the authors cannot confirm that it is the red wine causing this beneficial effect on the microbiota. They also point out that moderation is key.

"Although we observed an association between red wine consumption and the gut microbiota diversity, drinking red wine rarely, such as once every 2 weeks, seems to be enough to observe an effect," says Prof. Spector.

"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 with moderation."

Prof. Tim Spector