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 Women who ate freeze-dried blueberries for two months had lowered
blood pressure and increased levels of a chemical that relaxes blood
vessel walls.
“This tells us that blueberries may improve the health of blood
vessels in addition to reducing blood pressure,” said Sarah Johnson,
a nutrition and exercise researcher at Florida State University in
Tallahassee who led the study.
Johnson and her coauthors do not suggest that blueberries should
replace hypertension medications. But they say the berries might
help offset a tendency toward rising blood pressure and stiffening
blood vessels after menopause that raises women’s heart disease
risk.
Past research has suggested that blueberries may help lower blood
pressure, the authors write in the Journal of the Academy of
Nutrition and Dietetics. Some studies have also indicated that the
flavonoids and other healthy plant compounds in blueberries may help
to boost nitric oxide, a chemical that affects the cells that line
blood vessel walls.
The 48 women in the study were all past menopause, with an average
age of 55 and borderline high blood pressure.
For eight weeks, half the women consumed 22 grams (about 1.5
tablespoons) of freeze-dried blueberry powder every day (equivalent
to a cup of fresh blueberries) and the other half consumed an
identical-looking powder that didn’t contain blueberry.
At the beginning of the study, then four and eight weeks later,
researchers measured their blood pressure and the stiffness of their
arteries.
According to the American Heart Association, a blood pressure
reading of less than 120 mm Hg for the top number and less than 80
mm Hg for the bottom number is considered healthy. All the women in
the study were either close enough to the top of the healthy range
to be considered “pre-hypertensive” or already in the low end of the
hypertension range.
At the start, the average blood pressure in both groups of women was
138/79 mm Hg. After four weeks, it hadn't changed in either group.
After eight weeks, however, women who had been eating blueberry
powder had an average blood pressure of 131/75 mm Hg, representing a
drop of 5 to 6 percent. The readings of women eating the fake powder
had not changed.
The researchers also found that blood nitric oxide levels rose by 68
percent among women eating the real blueberry powder. The rise in
nitric oxide, which would relax and widen blood vessel walls, could
have contributed to their lower blood pressure, according to
Johnson.
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She said the blood pressure decrease in the blueberry group is
significant when compared to blood pressure medications and other
types of interventions, but that it also depends on the individual.
"People respond differently to medications and in some people
medications are even less effective than this," she said. "Some
medications may work better but may also have negative side
effects."
Freeze-dried blueberry powder is available in stores and online for
around $2 to $5 per ounce.
For women in the 50 to 55 age range who have borderline high blood
pressure, medication isn’t always recommended, according to Dr.
Chileshe Nkonde-Price, director of the Penn Women’s Cardiovascular
Center in Philadelphia, who was not involved with the study.
“Menopausal women who are often in that ‘gray zone’ can manage their
blood pressure by maintaining a normal body weight through diet and
exercise and watching their sodium intake,” she said. “But that can
be hard to implement in everyday life.”
Nkonde-Price thinks adding a cup of blueberries to a daily diet is
"simple" and something her patients can easily handle.
More research into understanding how blueberries affect arterial
function is needed, however, Nkonde-Price said.
“This study opens the gateway for other foods or other drugs that
could lower blood pressure through the same mechanism,” she said.
“I’d like to see more studies that show why foods or drugs work
through this pathway.”
SOURCE: http://bit.ly/1C5buor Journal of the Academy of Nutrition
and Dietetics, online January 8, 2015.
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