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500 milligrams of vitamin C daily reduced blood pressure by 3.84 millimeter
--But hold the supplements, for now, researchers say
Newswise
— Taking large doses of vitamin C may moderately reduce blood pressure,
according to an analysis of years of research by Johns Hopkins
scientists. But the researchers stopped short of suggesting people load
up on supplements.
“Our
research suggests a modest blood pressure lowering effect with vitamin C
supplementation, but before we can recommend supplements as a treatment
for high blood pressure, we really need more research to understand the
implications of taking them,” says Edgar “Pete” R. Miller III, M.D.,
Ph.D., an associate professor in the division of general internal
medicine at the Johns Hopkins University School of Medicine and leader
of the study published in the American Journal of Clinical Nutrition.
Roughly 30 percent of adults in the United States
have high blood pressure, or hypertension, an important risk factor for
heart disease and stroke. Successful treatment may include drugs,
exercise, weight loss, and dietary changes such as reducing salt intake.
Some experts believe that large amounts of vitamin C, an essential
micronutrient found primarily in fruits and vegetables, could lower
pressure as well, but randomized, controlled dietary intervention
studies — the gold standard of nutrition research — have produced mixed
results.
Miller
and his colleagues reviewed and analyzed data from 29 randomized,
controlled, previously published clinical trials that reported systolic
and/or diastolic blood pressure values and also compared vitamin C
intake to a placebo. What they found is that taking an average of 500
milligrams of vitamin C daily — about five times the recommended daily
requirement — reduced blood pressure by 3.84 millimeters of mercury in
the short term. Among those diagnosed with hypertension, the drop was
nearly 5 millimeters of mercury.
By
comparison, Miller says, patients who take blood pressure medication
such as ACE inhibitors or diuretics (so-called “water pills”) can expect
a roughly 10 millimeter of mercury reduction in blood pressure.
Five
hundred milligrams of vitamin C is the amount in about six cups of
orange juice. The recommended daily intake of vitamin C for adults is 90
milligrams.
“Although our review found only a moderate impact on blood pressure, if the entire U.S.
population lowered blood pressure by 3 milliliters of mercury, there
would be a lot fewer strokes,” Miller says. Miller cautions, however,
that none of the studies his team reviewed show that vitamin C directly
prevents or reduces rates of cardiovascular disease, including stroke.
Vitamin C may act as a diuretic
Scientists
have focused on vitamin C’s potential role in blood pressure reduction
because of the nutrient’s biological and physiological effects. For
example, vitamin C may act as a diuretic, causing the kidneys to remove
more sodium and water from the body, which helps to relax the blood
vessel walls, thereby lowering blood pressure.
Nutritional
supplements are a $28 billion-a-year industry, and marketing claims,
newspaper stories and testimonials often make them hard to resist,
Miller says. People often view supplements as a “natural alternative”
and preferable to drugs for high blood pressure or other ailments, he
adds, despite mounting evidence that many supplements don’t work and in
some cases may cause harm.
“People
love to take vitamins regardless of the evidence or lack of it,” Miller
says. “We’re trying to raise the bar and provide evidence-based
guidance about whether supplements help or actually do harm.” With
respect to vitamin C, he says, the jury is still out.
Acknowledgement by the Zestzfulness Team
The
above story is reprinted from the April 18, 2012 news release by Johns
Hopkins Medicine. The research finding was published online on the same
day in the American Journal of Clinical Nutrition: S. P. Juraschek, E.
Guallar, L. J. Appel, E. R. Miller. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr, 2012; DOI: 10.3945/ajcn.111.027995
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