Patients who took calcium increased their risk of a heart attack
by about 30 percent, according to researchers who said the use
of
dietary supplements for
preventing and treating osteoporosis should be reviewed.
In five studies with more than 8,000 patients, half of whom were
on calcium, the supplement users
had
143 heart attacks during the research compared with 111 for
people on placebo, scientists from New Zealand, the U.K. and the
U.S. wrote today in the British Medical Journal. The risk was
greatest when calcium intake from food was above average,
regardless of patients’ age or sex, according to the analysis.
Calcium supplements are prescribed to reduce the risk of
fractures and to prevent and treat osteoporosis, a thinning of
the bones. Previous studies had found no increased risk of heart
attacks with higher calcium intake from food. The analysis
suggests that the extra hazard is associated with supplements,
the medical journal said in an e-mailed statement.
“For patients who are at risk of heart disease and also
suffering from osteoporosis, perhaps calcium supplementation
should not be recommended,” Suzanne Steinbaum, director of women
and heart disease at the Heart & Vascular Institute of Lenox
Hill Hospital in New York and a spokeswoman for the Dallas-based
American Heart Association, said in a telephone interview.
Steinbaum wasn’t involved in the analysis, whose lead author is
Mark Bolland, a senior research fellow in the Department of
Medicine at the University of Auckland, in New Zealand.
The researchers also found a link between the calcium
supplements and a higher chance of stroke or sudden death,
though they said those results weren’t statistically
significant.
Heart Attacks
The analysis covered data from 11 trials, involving a total of
almost 12,000 participants over age 40 on average, about half of
whom were taking calcium supplements. For five of the trials,
data were available on whether the patients had suffered heart
attacks.
Calcium is the most prevalent mineral in the body and is found
in dairy products and some green vegetables. The human body uses
the mineral to strengthen its skeleton, storing 99 percent of
calcium in the bones and teeth.
The recommended daily calcium allowance in the U.K. is 1,300
milligrams for adults, according to the London-based Food
Standards Agency. Deficiencies are common in adults when the
process of bone breakdown starts to occur more often than bone
formation. Bone density can weaken, leading to osteoporosis.
Doctor’s Advice
“Patients with osteoporosis should generally not be treated with
calcium supplements, either alone or combined with vitamin D,
unless they are also receiving an effective treatment for
osteoporosis for a recognized indication,” John Cleland, a
professor of cardiology at the University of Hull in the U.K.,
and colleagues wrote in an editorial published along with the
analysis.
The researchers said they excluded from their analysis studies
that compared coadministered calcium and vitamin D supplements
with placebo. The findings may not be applicable to those
supplements, the authors wrote.
Osteoporosis affects an estimated 10 million Americans,
according to the Washington-based National Osteoporosis
Foundation. About 3 million people in the U.K. also have the
condition, according to National Osteoporosis Society, based in
Camerton, near Bath, England.
