Consuming blueberries can lower the risk of cardiovascular disease in postmenopausal women with high blood pressure, according to new research.

Consumption of 22 grams of freeze-dried highbush blueberry powder (equivalent to about 1 cup of fresh blueberries), mixed with water, taken daily for 12 weeks improved the function of the inner lining of blood vessels (called the endothelium), according to preliminary findings of a study. The finding was presented at the International Conference on Polyphenols and Health in London.

"We found an improvement in endothelial function which is important for human health, as endothelial dysfunction is linked to atherosclerotic cardiovascular disease development," said Sarah Ardanuy Johnson, from Colorado State University in the US. "We also found evidence that blueberries improved endothelial function through reductions in oxidative stress in the body," she said.

Oxidative stress is the imbalance between free radicals and antioxidants in the body and can damage cells and tissues, which promotes endothelial dysfunction and cardiovascular disease development. Previous research has demonstrated that polyphenols and polyphenol-rich foods like blueberries can reduce oxidative stress.

"To observe a direct link between reductions in oxidative stress and improvements in endothelial function in humans is exciting and provides insight into how blueberries promote cardiovascular health," Johnson said.

They performed a randomised clinical trial in 43 oestrogen-deficient postmenopausal women aged 45-65 years with elevated blood pressure or stage 1-hypertension.

"We don't fully understand the health benefits and how they interact in the human body," Johnson said of blueberries, "but we know that they're really important to human health." The team is exploring the role of the gut microbiome in determining the cardiovascular-protective effects of blueberries and their polyphenols.

Johnson said the team observed increases in blood metabolites that are products of the metabolism of anthocyanins (polyphenols found in blueberries that give them their blue colour) and metabolism of polyphenols by the gut microbiome.

The key takeaway is that there are benefits to consuming blueberries on a regular basis to help improve cardiovascular health, she said, adding that foods rich in phytochemicals may also include many fruits and vegetables, cocoa, chocolate, tea, nuts, legumes, whole grains, and spices.