FRIDAY, March 15 (HealthDay News) -- Black Americans who take
vitamin D supplements may significantly lower their blood pressure,
a new study suggests.
"Compared with other races, blacks in the United States are more likely to have vitamin D deficiency and more likely to have high blood pressure," said lead researcher Dr. John Forman, an assistant professor of medicine at the renal division of Brigham and Women's Hospital in Boston.
But among the black study participants, three months of
supplemental vitamin D was associated with a drop in systolic blood
pressure (the top number in a blood pressure reading) of up to 4 mm
Hg, the researchers found.
"If our findings are confirmed by other studies, then vitamin D supplementation may be a useful means of helping black individuals lower their blood pressure," Forman said.
Dr. Michael Holick, a professor of medicine, physiology and
biophysics at Boston University School of Medicine, said that
vitamin D may lower blood pressure by causing blood vessels to
relax, allowing for more and easier blood flow.
In addition, because many black Americans are deficient in
vitamin D, taking a supplement may benefit their health even more,
said Holick, who was not involved with the study.
"We are now beginning to believe that a lot of the health disparities between blacks and whites are due to vitamin D deficiency, including the risk for type 2 diabetes, heart disease, cancers and even infectious disease," he said.
Diet and sunlight are two natural sources of vitamin D in
humans. However, having dark-colored skin cuts down on the amount
of vitamin D the skin makes, according to the U.S. National
Institutes of Health.
For the study, published online March 13 and in the April print
issue of the journal
Hypertension, Forman's team randomly assigned 250 black
participants to one of three doses of vitamin D supplements or an
After three months, the researchers found that those taking
1,000 international units (IU) of vitamin D a day saw their
systolic blood pressure drop by 0.7 mm Hg. For those taking 2,000
IU, the drop was 3.4 mm Hg, and for those taking 4,000 IU, systolic
pressure dropped by 4 mm Hg.
In contrast, those receiving the placebo saw their systolic
blood pressure rise by 1.7 mm Hg, the researchers noted.
Forman said the gains from supplemental vitamin D were
significant, but modest. In addition, there were no changes in
diastolic blood pressure among those in any group.
Systolic blood pressure is pressure in the arteries when the
heart beats. Diastolic blood pressure, the bottom number, is
pressure in the arteries between heart beats, the study authors
"Hypertension is a leading cause of stroke, heart attack, heart failure, kidney failure and premature cardiovascular death, particularly in black men and women," said Dr. Gregg Fonarow, a spokesman for the American Heart Association, and a professor of cardiology at the University of California, Los Angeles.
Other studies of the effects of vitamin D on blood pressure have
been inconsistent and most studies have not included sufficient
numbers of black men and women or studied higher doses of vitamin
D, he said.
"These findings require replication in larger studies. It is also not clear that these findings would apply to other race and ethnic groups," Fonarow said.
Holick, however, said that most people should be taking a
vitamin D supplement. Endocrine Society committee guidelines
recommend that adults take 1,500 to 2,000 units of vitamin D daily,
"There is no downside to increasing vitamin D intake. It can reduce risk factors for cardiovascular disease as well as reducing the risk for cardiovascular disease," Holick said.
To learn more about hypertension, visit the
American Heart Association.
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