Calcium: Heart Risk for Older Women?
Study Shows Calcium Supplements May Up Heart Attack Risk in Postmenopausal Women
Jan.15 2008 -- Calcium
supplements, generally thought to preserve both bone and
heart health, may boost the risk of
heart disease in healthy postmenopausal women, according to New Zealand
"Loading with high doses of calcium reduces bone loss but at a cost in
heart health that is not justified," says researcher Ian Reid, MD,
professor of medicine and endocrinology at the University of Auckland.
But a U.S. expert on calcium supplementation says the findings may be a
fluke and at this time don't warrant any change in the recommendation to get
sufficient calcium through
diet and supplements.
Calcium, Heart Attack Study Details
Reid and his colleagues followed 1,471 healthy postmenopausal women, ages 55
and above, assigning half to get a daily calcium supplement of 1,000 milligrams
and half to placebo pills. The average age in both groups was 74.
Calcium supplements are typically prescribed to women after menopause to
preserve bone health, and some studies suggest it might also protect heart
health by improving the ratio of good
cholesterol to bad cholesterol.
The New Zealand researchers initially conducted the study to look at the
effect of calcium on bone health, says Reid, who has received research support
from calcium supplement manufacturers. This study is what is known as a
secondary analysis. Researchers evaluated the women's calcium intake from diet
and examined them every six months for five years, looking for reports of
stroke, or sudden death.
The women in the supplement group got 861 milligrams of calcium from diet
per day, on average, boosting their total daily intake to 1,861. The placebo
group averaged about 853 milligrams of calcium daily from their diet.
(Has your doctor
talked to you about heart risks? Talk with others on WebMD's Bone Health and
Osteoporosis message board.)
Calcium, Heart Attack Results
To obtain a more complete picture, the researchers also looked for events
not reported at the visits by checking hospital admissions and reviewing death
certificates of those who had died.
Heart attacks were more common in the calcium group, with 31 women on
supplements having 36 heart attacks compared to 21 women on placebo having 22
heart attacks during the follow-up period.
The risk of a heart attack was about 1.5 times greater for those in the
supplement group, but the link did not reach statistical significance.
Considered together, strokes, heart attack, or sudden death were more common
in those on supplements than on placebo, but the differences -- when taken as a
whole -- were statistically only of borderline significance, Reid's team
The researchers took into account such factors as cigarette
high cholesterol, and
blood pressure problems.
Calcium, Heart Attack: What's the Mechanism?
Reid cautions that the findings must be replicated and plans to do more
research on the proposed link.
But he speculates that the calcium supplements may elevate blood calcium
levels and possibly speed calcification in blood vessels, which is known to
predict the rates of vascular problems such as heart attack.