Study: Are Calcium Supplements Bad for the Heart?

Previously published studies suggest no-or even an inverse-association between dietary calcium and adverse heart events, such as stroke and heart disease. The science on calcium supplements, however, has not been so favorable, at times pointing to increased risk of heart attack. Two recent meta-analyses, here and here, support the notion.

Now, results of a population study support the notion that calcium supplements (not calcium in the diet) may increase one’s risk of heart problems.

Researchers from the German Cancer Research Center (Heidelberg, Germany) pulled data from nearly 24,000 men and women who participated in the European Prospective Investigation into Cancer and Nutrition study, a population-based study involving extensive food frequency questionnaires and subject self-reporting of dietary supplement use. All subjects were free of major heart disease events at the start of the study.

After 11 years of follow-up, 260 cases of stroke, 354 cases of heart attack, and 267 deaths related to heart disease were documented.

Compared to subjects who ate the lowest range of calcium foods, those who ate significantly more (in the second highest quartile) showed a significantly reduced risk of heart attack.

Calcium supplement users showed a statistically significant increase in heart attack risk compared to non-calcium supplement users. The association was even stronger if the subject only took calcium supplements, according to the study.

“The underlying mechanisms of the adverse effect of calcium supplements on myocardial infarction risk might be related to the acute increase in serum calcium, which has been observed after ingestion of calcium supplements, but not after eating calcium-rich foods,” wrote the study’s author. “Several studies have observed a positive association between serum calcium levels and vascular calcification.”

But, while the study seems well-powered with a large sample size and years of follow-up, supplement industry associations are quick to point out some serious caveats regarding end points and distribution of lifestyle habits across supplement users and non-users.

Taylor Wallace, PhD, senior director of scientific and regulatory affairs at the Council for Responsible Nutrition (Washington, DC) notes that the original EPIC-Heidelberg study wasn’t designed to measure adverse heart events. He adds that the calcium supplement group included more subjects with high cholesterol at baseline and more smokers (who were more likely to smoke longer in life).