New research carried out at Queen's University has found part of the reason why consuming flavonoid-rich foods like red wine, berries, apples, pears and tea on a regular basis could help reduce blood pressure.

A higher intake of flavonoid-rich foods is already associated with a clinically relevant reduction in blood pressure levels.

However, new research led by Prof. Aedin Cassidy from the Institute for Global Food Security (IGFS) at Queen's University Belfast has made findings about the relationship between flavonoids, blood pressure and our microbiome - and finds that the effect is partly because of how the gut microbiome metabolises flavonoids.

Prof. Cassidy, chair of nutrition and preventive medicine at IGFS, was lead investigator in the study of over 900 adults which has been published in Hypertension, an American Heart Association journal.

There is mounting evidence from population-based studies and clinical trials that a higher intake of flavonoids and flavonoid-rich foods can improve heart health, but for the first time, this data highlights the key role of the gut microbiome in explaining the associations between flavonoid-rich foods and blood pressure.

Up to 15% of the observed association was explained by the gut microbiome suggesting these microbes play a key role in metabolising flavonoids to enhance their cardioprotective effects.

The study of more than 900 German adults found that higher habitual intakes of flavonoid-rich foods, specifically berries, red wine, apples/pears were associated with clinically relevant reductions in systolic blood pressure and pulse pressure, greater microbial diversity and lower abundance of Parabacteroides.

These blood-pressure-lowering effects are achievable with simple changes to the daily diet.

Eating approximately 1.5 servings of berries/day was associated with a 4.1mmHg reduction in systolic blood pressure, and 12% of the association was explained by gut microbiome factors.

Drinking around three glasses/week of red wine was associated with 3.7mmHg lower systolic blood pressure levels, of which 15% could be explained by the gut microbiome.

Prof. Cassidy, also based in the School of Biological Sciences at Queen's University Belfast said: “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.

"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.”

The flavonoid–gut microbiome interaction associated with blood pressure highlighted in this paper suggests research should focus on inter-individual variability in the gut microbiome in mediating the cardiovascular benefits.

The analysis of habitual flavonoid intake with gut microbiome and blood pressure levels found:

Researchers from Kiel University were also major contributors to the research, and the PopGen cohort was led by Prof. Wolfgang Lieb.

The research was funded by grants from the German Research Foundation and the German Federal Ministry of Education and Research.