HEART
August 12, 2010

Calcium: Trouble for the Heart?

Calcium supplements may strengthen the bones, but they may also raise the risk of heart attack, researchers say.

Though many people may take calcium supplements to ward of osteoporosis, a new study suggests that doing so may up one's risk of heart attack. And in this case, the risk to the heart may actually outweigh the benefits to the bones.

The study, published in the July 29, 2010 issue of BMJ, reviewed several earlier studies that included almost 12,000 participants who were given either 500 mg/day or more of calcium supplements, or placebo. The researchers compared how many of the participants in each group suffered from heart trouble over a period of four years.

Getting calcium through the diet alone may be a good way to go: dietary calcium does not raise blood calcium levels in the same way that supplements do, and earlier studies did not find the same heart risks associated with calcium in the diet.

They found that the people who took calcium supplements were about 30% more likely to have myocardial infarction (heart attack) during the study period. Participants were also more likely to have a stroke and to die, but these results weren't statistically significant, meaning that they could have been due to chance.

What do the findings mean for the general population? The authors, led by Ian R. Reid, did the math, and calculated that if 1,000 people took calcium supplements for five years, this "would cause an additional 14 myocardial infarctions, 10 strokes, and 13 deaths, and prevent 26 fractures." Since the number of bad outcomes totals 37, and the number of factures prevented is only 26, it seems like risks of calcium may outweigh its benefits.

It's important to note, however, that the researchers excluded studies in which calcium supplements were given along with vitamin D. Since two often come as a pair – as vitamin D aids in the body's absorption of calcium – the study's results may not apply to what happens when the two are taken together.

Getting calcium through the diet alone may be a good way to go: dietary calcium does not raise blood calcium levels in the same way that supplements do, and earlier studies did not find the same heart risks associated with calcium in the diet.

Clearly more research is needed to determine just how calcium may affect heart health. Given the number of people who take calcium supplements, though, Reid and his team suggest that a "reassessment of the role of calcium supplements in the management of osteoporosis is warranted."

Reid is affiliated with the University of Auckland, New Zealand.

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