A study published in JAMA Internal Medicine suggested a high intake of supplemental calcium may be associated with an increased risk of cardiovascular disease (CVD) deaths among men, but not women.

Qian Xiao, PhD, of the National Cancer Institute, Bethesda, MD, and colleagues examined whether the intake of dietary and supplemental calcium was associated with mortality from total CVD, heart disease and cerebrovascular diseases. Study participants were 388,229 men and women ages 50 to 71 years from the National Institutes of Health-AARP Diet and Health Study in six states and two metropolitan areas from 1995 through 1996.

“In this large, prospective study we found that supplemental but not dietary calcium intake was associated with an increased CVD mortality in men but not in women,” the authors concluded. During an average 12 years of follow-up, 7,904 CVD deaths in men and 3,874 CVD deaths in women were identified and supplements containing calcium were used by 51% of men and 70% of women. Compared with non-supplement users, men with an intake of supplemental calcium of more than 1,000 mg/day had an increased risk of total CVD death, more specifically with heart disease, but not significantly with cerebrovascular disease death.

For women, supplemental calcium intake was not associated with CVD death, heart disease death or cerebrovascular disease death. Dietary calcium intake also was not associated with CVD death in men or women.

Taylor Wallace, PhD, senior director, scientific and regulatory affairs, Council for Responsible Nutrition (CRN), Washington, D.C., noted the study had several “design defects.” “The National Institutes of Health–AARP Diet & Health Study was originally designed by researchers at the National Cancer Institute to look specifically at epidemiologic investigations of diet and cancer, not to measure cardiovascular or cerebrovascular outcomes. It is also important to consider that dietary supplement usage has increased dramatically in the last two decades. This includes calcium supplement usage, which has increased among men in the past two decades as dairy consumption has decreased and the incidence of osteoporosis among this population has become increasingly evident. The results of this study are most likely confounded by the lack of data collected during the 11-year follow up because the number of baseline non-users who became users of calcium supplements was likely to have increased substantially.”

Dr. Cara Welch, senior vice president of scientific and regulatory affairs with the Natural Products Association (NPA), Washington, D.C., said this study should not cause anyone to stop taking calcium supplements, and NPA has long recommended consumers discuss calcium intake with their healthcare professional. “It’s important for all age groups to maintain an adequate level of calcium as part of a healthy lifestyle. Dietary supplementation is both safe and effective for anyone who isn’t getting enough calcium from their diet. Calcium is an essential nutrient and the known benefits far outweigh the suggested detriments from this study.”

This study fails to capture all the pertinent information regarding duration of calcium supplementation or other nutrients, Dr. Welch continued. “Additionally, the study did not find any increased risk for women taking calcium supplements so there are certainly more questions to answer before coming to a conclusion. We agree with the related commentary to this study that, in their words, ‘More large studies are needed to further assess the potential health risks or benefits of calcium supplement use.’”

Dr. Wallace agreed that consumers should “rest assured that supplemental calcium is safe and effective for ensuring optimal bone health.” He went on to say the safety and benefit of calcium supplementation is well established. “This study proves inconsistent with a recent wave of new research that concludes that calcium supplementation is beneficial to bone health, and also poses no risk to cardiovascular health.”