Calcium: Heart Risk for Older Women?

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
researchers.

"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
heart attack ,
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
found.

The researchers took into account such factors as cigarette
smoking ,
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.

Second Opinion: Calcium, Heart Attacks

The link between calcium supplements and heart attack suggested by the New
Zealand team "seems implausible," says Robert P. Heaney, MD, John A.
Creighton University professor at Creighton University in Omaha, Neb., and a
long-time researcher of calcium's effect on health.

Typically, Heaney tells WebMD, "Extra calcium doesn't build up in your
arteries. The body regulates the blood concentration of calcium.'' Only in
people who have lost the ability to regulate calcium levels could the blood
concentration of calcium increase, he says, and this condition is rare.

Calcium and Heart Healh Advice

Women should keep taking the recommended amounts of calcium, Heaney says.
"Postmenopausal women should be getting 1,500 milligrams [a day] through
diet and supplements," he says.

The levels recommended by the Institute of Medicine are a bit lower: 1,200
milligrams of calcium for men and women ages 51 and older, and 1,000 milligrams
for those 19 to 50.

"Even if it turns out this [proposed link between calcium supplements
and heart attacks] is true and replicated [with further research] you have to
weigh that against fracture protection," Heaney says of calcium
supplements.

Reid disagrees, suggesting women over the age of 70 and some others should
rethink calcium supplements.

"It is likely that this is primarily a problem for elderly women because
they are more likely than younger subjects to have prevalent coronary heart
disease," he tells WebMD. "Therefore it seems wise to advise against
[high amounts of] calcium supplementation in those over the age of 70 years and
in those known to have coronary heart disease. Aiming at a total calcium intake
of approximately 1 gram [1,000 milligrams] a day [equivalent to four servings
of dairy products] seems sensible in these subjects."

For instance, a woman who took in 500 milligrams of calcium from foods
should take no more than 500 milligrams in supplements daily, he says.

Younger women can continue supplementing without worry, he says. "At
present, there is no evidence of adverse cardiovascular effects of calcium
supplementation in younger women, so the conventional use of calcium
supplements seems reasonable in these subjects."

By Kathleen Doheny
Reviewed by Louise Chang
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