Biological compounds found in blueberries may lower the risk of developing high blood pressure, according to a new study from the University of East Anglia and Harvard University.
The researchers, which tracked volunteers over 14 years, found that the people who consumed at least one serving of blueberries per week were 10 percent less likelyto develop high blood pressure, also known as hypertension, than those who ate none.
Blueberries contain compounds known as anthocyanins, a type of flavonoid which are antioxidant and have been shown to reduce the risk of cardiovascular disease. But the new study showed that anthocyanins in blueberries may work better than other flavonoids at keeping blood pressure low.
"Of all of the flavonoids, anthocyanins seem to be the most protective in terms of reducing risk of hypertension," said study researcher Aedin Cassidy of the University of East Anglia.
In the study, those with the highest amount of anthocyanins in their diets - mostly from eating high amounts of blueberries and strawberries - saw an 8 percent reduction in their risk of high blood pressure, compared with those who ate the least amount of anthocyanins. The researchers found no effect on hypertension risk in people who ate the highest amounts of other types of flavonoids.
The effects of the anthocyanins were seen even after the researchers took into account other factors that could affect the development of hypertension, including smoking, physical activity, alcohol consumption and body mass index.
Previous studies found that foods rich in flavonoids reduce blood pressure, but in some of these studies, the dose of flavonoids was beyond what people typically consume. And no studies based on observations of people's diets have measured the effects of different classes of flavonoids on high blood pressure, the researchers said.
Cassidy and her colleagues analysed the diets of 134,000 women and 47,000 men over 14-year periods. None of the participants had high blood pressure at the start of teh study. Every four years, the participants completed questionnaires about their diet.
In addition to the entire group of anthocyanins, the researchers saw blood pressure-reducing effects from certain other compounds within other flavonoid groups. For instance, a compound found in dark chocolate was associated with a reduced risk of hypertension. The compounds that seemed to reduce hypertension risk all have a similar structure, which may play a role in their ability to affect blood pressure, Cassidy said.
She commented that flavonoids may reduce hypertension by increasing the output of nitric oxide, which relaxes blood vessels and improves blood flow. The study was published in the February issue of the American Journal of Clinical Nutrition.