Findings from the study highlights intake of flavonoid-rich foods such as berries, red wine, apples/pears were associated with clinically relevant reductions in systolic blood pressure and pulse pressure,
The Queen’s University Belfast research also notes a greater microbial diversity and lower numbers of Parabacteroides, a bacterium linked to high blood pressure.
“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,” explains lead investigator Professor Aedín Cassidy, Chair in nutrition and preventive medicine at the Institute for Global Food Security at Queen’s.
“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.
“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.”
Professor Cassidy took charge of the study that enrolled over 900 adults. Here, gut microbiome composition was sequenced, and biochemical, phenotypic and dietary information was taken along with Systolic and Diastolic Blood Pressure (SBP & DBP).
Data analysis revealed subjects who had the highest intake of flavonoid-rich foods had lower systolic blood pressure levels.
The findings extended to a greater diversity in their gut microbiome than participants who consumed the lowest levels of flavonoid-rich foods.
More results revealed consumption of 80 grams (g) of berries a day coincided with an average reduction in SBP levels of 4.1 mm Hg, and about 12% of the association was explained by gut microbiome factors.
Finally, drinking 250 millilitres (ml) of red wine a week, just under three small glasses, was linked with an average of 3.7mm Hg lower SBP level of which 15% could be explained by the gut microbiome.
“For red wine, this could be explained by a combination of alpha diversity and higher relative abundance of unclassified Ruminococcaceae,” the study suggests.
“Alpha diversity has shown to be lower in patients with hypertension relative to controls and increased with higher intakes of red wine.
“Hypertension is associated with changes in gut pathology including increased permeability, inflammation, and perfusion.
“These changes in gut pathology likely explain the alterations in diversity of microbial communities seen in hypertension, although it is not clear if these physiological changes are a cause or a consequence of hypertension.”
In regard to the influence of Parabacteroides on blood pressure, the team proposed a mechanism that mentions the production of succinate as a contributor in the development of hypertension.
However, in a recent study, although Parabacteroides distasonis was shown to generate succinate in the gut, this was associated with reduced weight gain and hyperglycaemia in mice.
Furthermore, in vitro studies have shown that apple intake increases abundance of Parabacteroides, and findings from mice models suggest that higher intake of lingonberries increase relative abundance of Parabacteroides by up to 15%.
Strengths and limitations
Despite the promise of the study’s findings, the team acknowledged the limited associations of flavonoid subclasses with the gut microbiome, recognising the role phytochemicals, such as chlorogenic acid, ellagitannins, and resveratrol, could play in the observed associations.
Future work should consider measuring urinary flavonoid metabolite concentrations as potential biomarkers of intake.
“This bidirectional flavonoid–gut microbiome interaction associated with BP suggests future trials should stratify participants according to metabotypes to more accurately investigate the relative importance of metabolism and the gut microbiome on moderating the effect of flavonoids on BP,” they conclude.
“A greater understanding of the interindividual variability of flavonoid metabolism will elucidate why flavonoid-rich foods may provide greater cardiovascular protection to some more than others.”
Published online: doi.org/10.1161/HYPERTENSIONAHA.121.17441
“Microbial Diversity and Abundance of Parabacteroides Mediate the Associations Between Higher Intake of Flavonoid-Rich Foods and Lower Blood Pressure.”
Authors: Amy Jennings et al.