A diet rich in flavonoid compounds is linked to lower blood pressure, a study has found, and the association is partly explained by an improved gut microbiome.


Flavonoids are compounds found in plants. Foods rich in flavonoids include vegetables, fruits such as apples, pears and berries, and chocolate, tea and wine. In the body, they act as antioxidants, and provide protection from ultraviolet rays. They are broken down by the gut microbiome.

“Our gut microbiome plays a key role in metabolising flavonoids to enhance their cardioprotective effects, and this study provides evidence to suggest these blood pressure-lowering effects are achievable with simple changes to the daily diet,” said Prof Aedín Cassidy at Queen’s University in Belfast, Northern Ireland, lead investigator of the study.

The World Health Organization lists cardiovascular disease (CVD) as the leading cause of death worldwide in 2019. Previous research has reported differences in the composition of the gut microbiome between those with and without CVD, and that flavonoids may reduce the risk of heart disease.

The team of researchers, based at Queen’s University and Kiel University, Germany, examined the link between eating flavonoids, blood pressure, and the gut microbiome. They studied 904 adults from Germany’s PopGen biobank, 57 per cent of whom were men, and asked them to evaluate their food intake with a self-reported questionnaire. The team also analysed their gut microbiome through bacterial DNA in stool samples, and measured their blood pressure.

The researchers also took asked the participants about several other factors, including BMI, family history of CVD, physical activity and medication use. After taking all of these into account, they found that those with the highest intake of flavonoids had lower blood pressure and a greater diversity in their gut microbiome.

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Eating 1.6 servings of berries a day reduced systolic blood pressure by 4.1mmHg, while 2.8 glasses of red wine per week brought a reduction of 3.7mmHg.

The team found that up to 15.2 per cent of the reduction in blood pressure could be explained by the increased gut microbiome diversity.

“Our findings indicate future trials should look at participants according to metabolic profile in order to more accurately study the roles of metabolism and the gut microbiome in regulating the effects of flavonoids on blood pressure,” said Cassidy.

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“A better understanding of the highly individual variability of flavonoid metabolism could very well explain why some people have greater cardiovascular protection benefits from flavonoid-rich foods than others.”

Reader Q&A: Do we get our gut bacteria microbiome before or after birth?

Asked by: Michael Chandler, Hereford

We each have trillions of bacteria living in our gut and this microbiome plays important roles in digestion and fighting disease. Their origins have long been debated, but two large-scale studies in 2019 offered some answers.

In one, researchers retrieved more than 500 placentas from women shortly after giving birth, and found the healthy placentas were sterile. Another study reported that babies delivered by caesarean lack certain strains of beneficial bacteria. Taken together, the research indicates we pick up our microbiome during and shortly after birth.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.