There's even more evidence that a well-known superfood really does the job.
Just one cup of blueberries per day could be the key to reducing blood pressure and arterial stiffness.
That's the finding of a Florida State University study published in the Journal of the Academy of Nutrition and Dietetics.
Regular consumption of blueberries could potentially delay the progression of pre-hypertension to hypertension, therefore reducing cardiovascular disease risk, especially in postmenopausal women, said researcher Sarah Johnson.
"Cardiovascular disease is the leading cause of death in the United States," she said. "Once women go through menopause, this puts them at an even greater risk for it. Our findings suggest that the addition of a single food, blueberries, to the diet may mitigate the negative cardiovascular effects that often occur as a result of menopause."
Over an eight-week period, 48 postmenopausal women with pre- and stage-1 hypertension were randomly assigned to receive either 22 grams of freeze-dried blueberry powder -- the equivalent to one cup of fresh blueberries -- or 22 grams of a placebo powder. Participants, meanwhile, continued their normal diet and exercise routines.
At the beginning of the study, the team took participants' blood pressure and measured their arterial stiffness and select blood biomarkers.
At the end of the eight weeks, participants receiving the blueberry powder on average had a 7 mmHg (5.1 per cent) decrease in systolic blood pressure, which is the top number in the blood pressure reading that measures the pressure in the arteries when the heart beats. They also saw a 5 mmHg (6.3 per cent) reduction in diastolic blood pressure, or the bottom number measuring the pressure in the arteries between heartbeats.
Additionally, participants in the blueberry-treated group had an average reduction of 97 cm/second (6.5 per cent) in arterial stiffness.
They also found that nitric oxide, a blood biomarker known to be involved in the widening of blood vessels, increased by 68.5 percent.
That is important, Johnson said, because arterial stiffness and the narrowing of blood vessels are both a part of hypertension. This rise in nitric oxide helps explain the reductions in blood pressure.
Previous studies on blueberries have shown positive effects on cardiovascular risk factors including blood pressure, but they all included large amounts of blueberry powder consumption, anywhere from 50 grams to 250 grams. In the case of 250 grams, that would translate to more than 11 cups of fresh blueberries, which may not be realistic for people to consume on a regular basis.
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