Calcium Supplements Linked to Increased Heart Attack Risk in Post-Menopausal Women: Study

April 20, 2011— -- A year after Marie Hoffmann began menopause, a bone density test revealed signs of osteoporosis. Her doctor started her on the bone-building drug Fosamax and a calcium supplement, which helped strengthen her brittle bones and downgrade her condition to osteopenia.

Hoffmann, a 62-year-old from Kansas City, Mo., said she's happy with the results of her treatment -- and understandably so. Her mom and aunt both died because of complications from osteoporosis, she said. And for someone who never liked milk, calcium supplements seem a logical addition.

But new research may cause worry among some like Hoffmann. In an analysis of past research that has already sparked debate among medical experts, researchers suggests calcium supplements might boost the risk of heart attacks.

Using data from the Women's Health Initiative Calcium/Vitamin D Supplementation Study -- a seven-year trial in 36,282 postmenopausal women -- Dr. Ian Reid from the University of Auckland in New Zealand and colleagues concluded that women who took calcium supplements had a 13-to-22 percent greater risk of having a heart attack than women who did not. The risk went up regardless of whether the women also took vitamin D, which promotes calcium absorption and bone mineralization. The researchers also found a milder increase in stroke risk among women taking the supplements.

"When these results are taken together with the results of other clinical trials of calcium supplements, with or without vitamin D, they strongly suggest that calcium supplements modestly increase the risk of cardiovascular events, particularly myocardial infarction," Reid and colleagues wrote in the report published today in BMJ. "These data justify a reassessment of the use of calcium supplements in older people."

But the findings, which stem from a review of old data rather than new observations, conflict with earlier reports from the Women's Health Initiative (WHI).

"In other WHI analyses, we found no association between [calcium and vitamin D] supplementation and [coronary heart disease] or stroke death and neither did these authors," said Andrea LaCroix, a professor of epidemiology at the Fred Hutchinson Cancer Research Center and a co-author of the earlier WHI studies.

LaCroix says "exploratory" reviews of past studies can often lead to findings that result from chance alone. But Reid and colleagues argue that the heart attack risk went unnoticed in earlier investigations because so many study subjects were taking calcium supplements outside of the study.