Flavonoids—compounds found in plant-based foods such as berries, apples, tea, wine, and dark chocolate—are known for their health benefits, particularly in strengthening the cardiovascular system. At the same time, scientists have demonstrated a link between the composition of microorganisms in the human digestive tract and cardiovascular disease.
Researchers from Queen's University Belfast, along with German colleagues from Kiel University and the University Hospital Schleswig-Holstein, suggested that these three factors are interconnected. To test their hypothesis, they evaluated the amount and frequency of consuming flavonoid-rich foods and measured the abundance of Parabacteroides—gut bacteria that break down flavonoids—in more than 900 German adults from the German PopGen Biobank.
Calculations were based on a self-reported food frequency questionnaire featuring 112 products for which the USDA has published flavonoid content. The participants' gut microbiome was assessed using bacterial DNA isolated from stool samples.
To adjust the results, the researchers also gathered information on the participants' lifestyles, including body mass index, sex, age, smoking status, medication use, physical activity, daily calorie and fiber intake, and family history of ischemic heart disease.
The results showed that those who consumed more berries, apples, pears, and wine had lower systolic blood pressure levels, as well as greater gut microbiome diversity, compared to those who consumed fewer dietary flavonoids.
"The gut microbiome plays a key role in metabolizing flavonoids to enhance their cardioprotective effects, and our study provides evidence that these blood pressure-lowering effects are achievable with simple changes to the daily diet," said the study’s lead investigator, Dr. Aedín Cassidy, a professor of nutrition and preventive medicine at the Institute for Global Food Security at Queen's University, in an American Heart Association press release.
The authors note that the study did not focus on all foods and beverages containing flavonoids, but only on specific types of berries and fruits, as well as red wine. According to the American Heart Association, drinking alcohol, particularly red wine, can be part of a healthy diet. However, it should be consumed in moderation—no more than one glass a day for women and two for men.
As for us, we can only wholeheartedly agree.
