Researchers found volunteers consuming 200 grams (g) of the fruit for one month had blood vessel function improvement and a decrease in systolic blood pressure in healthy subjects.
The team from King's College London suspected the anthocyanin responsible for the blue colour of blueberries might be responsible for this effect having observed similar results in previous studies.
“Although it is best to eat the whole blueberry to get the full benefit, our study finds that the majority of the effects can be explained by anthocyanins,” said Dr Ana Rodriguez-Mateos, lead researcher from the Department of Nutritional Sciences at the university.
"If the changes we saw in blood vessel function after eating blueberries every day could be sustained for a person's whole life, it could reduce their risk of developing cardiovascular disease by up to 20%."
The vascular effects of anthocyanins, which mainly circulate in blood as phenolic acid metabolites, have been well documented.
Blueberries and metabolic syndrome
Blueberries are a rich source of phenolic compounds that encompass flavonoids, phenolic acids, and stilbenes, which are known to have high antioxidant capacity demonstrating promising benefits as a functional food for vascular health.
The fruit’s qualities were a subject of a study, where along with strawberries and cranberries, were put forward for a beneficial role in tackling metabolic syndrome, a prediabetic state characterised by several cardiovascular risk factors.
In this study, 40 healthy volunteers were randomly given either a drink containing 200g of blueberries, or a matched control drink daily for one month.
The researchers kept an eye on chemical levels in the volunteer’s blood also noting blood pressure and flow-mediated dilation (FMD) of the brachial artery.
The FMD measures how wide the artery stretches with increased blood flow, which is thought to be a reliable biomarker of cardiovascular disease risk.
In the second part of the investigation, the team looked at the effects of a blueberry drink against samples of purified anthocyanins.
The team also compared the blueberry drink with control drinks that contained similar levels of either fibre, mineral or vitamins found in blueberries.
Results revealed effects on blood vessel function were seen only two hours after the blueberry drink consumption and were sustained for one month even after an overnight fast.
During the trial period blood pressure reduced by 5mmHg – a comparable result to pharmaceutical drugs designed to lower blood pressure.
Further results noted that the drinks containing purified anthocyanins resulted in improvements in endothelial function, regulating blood pressure.
Neither the control drink, the control with fibre or the control with minerals and vitamins had a significant effect on FMD at two and six hours after consumption.
Metabolomics and nutrigenomic analysis found daily blueberry consumption led to expression of 608 genes and 3 microRNAs.
“Patterns of 13 metabolites were independent predictors of gene expression changes and pathway enrichment analysis revealed significantly modulated biological processes involved in cell adhesion, migration, immune response, and cell differentiation,” the study stated.
“Our results identify anthocyanin metabolites as major mediators of vascular bioactivities of blueberries and changes of cellular gene programs.”
Source: The Journals of Gerontology
Published online: doi.org/10.1093/gerona/glz047
“Circulating anthocyanin metabolites mediate vascular benefits of blueberries: insights from randomized controlled trials, metabolomics, and nutrigenomics.”
Authors: Ana Rodriguez-Mateos et al.