Flavonoid-rich foods such as berries, apples, pears, and wine, appear to have a positive effect on blood pressure levels, and this protective effect may be at least partly explained by the changes that flavonoids exert on bacteria in the gut, according to a new study published in the American Heart Association journal Hypertension.
 
Flavonoids, a family of phytochemicals linked to several metabolic and other cardiovascular health benefits, are generally believed to have a mechanism of action which can modulate inflammation and exert strong antioxidant properties. The mechanism of action found in the present study suggests that gut bacteria may play a strong role in the activity flavonoids apparently have in regard to blood pressure – gut microbial compositions are highly variable on an individual basis, and the more diverse one’s gut microbiome was in the trial, the more likely they were to experience significant improvements to blood pressure through high flavonoid intake.
 
“Our gut microbiome plays a key role in metabolizing 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,” Aedin Cassidy, PhD, lead author of the study and professor of nutrition and preventive medicine at the Institute for Global Food Security at Queen’s University in Belfast, Northern Ireland, said.
 
The authors of the study noted that previous research has indicated Bifidobacterium and Lactobacillus strains convert flavonoids into metabolites which are very well-established to have cardio-protective benefits, such as improving lipid profiles, decreasing inflammation, and more.
 
The authors of the study analyzed data from 904 adults between the ages of 25 and 82, 57% of whom were men, from Germany’s PopGen biobank, and evaluated their food intake, gut microbiome, and blood pressure levels together with other clinical and molecular phenotyping and regular follow-up examinations. Based on the quantity at which participants ate 112 flavonoid-rich foods, with flavonoid values assigned to foods based on USDA data.
 
The gut microbiomes of the participants were assessed by fecal bacterial DNA examination extracted from stool samples. The researchers also adjusted for cofounding factors such as sex, age, smoking status, medication use, physical activity, family history of coronary artery disease, the number of daily calories and fiber consumed, and BMI.
 
There was a variety of associations between flavonoid-rich foods and blood pressure reductions, and the extent to which gut microbiota appeared to be involved in the process appeared to vary according to the researchers’ analysis. Overall, participants with a highest intake of flavonoid-rich foods, including berries, red wine, apples, and pears, had lower systolic blood pressure levels as well as a greater diversity in their gut microbiome than participants who consumed the lowest levels of flavonoid-rich foods. Up to 15.2% of the association between flavonoid-rich foods and systolic blood pressure could be explained by the diversity found in the participants’ gut microbiome, the authors noted. Specifically, it was found that 1.6 servings of berries per day was linked to an average reduction in systolic blood pressure levels of 4.1 mmHg, and about 12% of that association was also linked to gut microbiome factors. Additionally, it was found that drinking 2.8 glasses of red wine per week was associated with an average of 3.7 mmHg lower systolic blood pressure, of which 15% could be explained by changes in the gut microbiome.
 
“The magnitude of the association between anthocyanin intake and systolic blood pressure (-4.8 mmHg) was similar to our previous observations in a female cohort. A reduction in SBP of this scale is likely to have clinical benefits with previous studies showing that 5 mmHg reduction in SBP reduces stroke risk by 13% over 295,652 patient-years,” the authors of the study concluded.”
 
“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,” Cassidy added. “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.”