COMMENTARY

Trash the Calcium, Save the Patient

A Best Evidence Review

Charles P. Vega, MD

Disclosures

March 07, 2013

In This Article

Skip the Calcium, Save the Patient

The Study

Xiao Q, Murphy RA, Houston DK, Harris TB, Chow W, Park Y. Dietary and supplemental calcium intake and cardiovascular disease mortality: The National Institutes of Health-AARP Diet and Health Study. JAMA Intern Med. 2013;1-8. [Epub ahead of print]

Introduction

Scant evidence supports the notion that calcium supplements alone significantly decrease the risk for osteoporotic fracture, yet these supplements remain one of the most popular treatments taken by adults in the United States. In addition, there is increasing evidence that calcium may contribute to a higher risk for cardiovascular disease (CVD). The current study uses a large cohort of adults to examine how dietary calcium and calcium supplements affect the risk for CVD among women and men.

Background

A new review of supplement use, based on data from the National Health and Nutrition Examination Survey,[1] concluded that nearly one half of adults in the United States use dietary supplements, but relatively few of these individuals take supplements on the recommendation of their physician or other healthcare provider. This study found that 49% of a sample of US adults had used of supplements in the past 30 days. Factors associated with a higher rate of supplement use included female sex, non-Hispanic white race, and a subjective measurement of health as very good or excellent.

Although the most popular reason for using supplements in this study was to improve or maintain health in general, "bone health" was cited by 25% of respondents as a reason for taking these agents. Products that contained calcium were the second most common supplements overall. However, only 23% of supplements were recommended by the individual's physician.

What is the evidence for supplement use, particularly when it comes to calcium? A meta-analysis of 29 studies found that calcium use alone was associated with a nonsignificant reduction in the risk for fracture.[2] However, the use of calcium with vitamin D reduced the risk for fracture by 12%. Vitamin D alone at doses of 800 IU or more daily also significantly reduced the risk for fracture (relative risk, 0.84; 95% confidence interval [CI], 0.75-0.94).

In another meta-analysis, total calcium intake did not alter the risk for hip or total nonvertebral fracture.[3] More disturbing was the finding that calcium supplementation was associated with a higher risk for hip fracture compared with placebo.

Supplements are also frequently used to prevent poor health outcomes. There is limited evidence that high-dose treatment with vitamin D supplements can reduce the risk for incident cancer, particularly colorectal cancer.[4] However, little evidence suggests that treatment with calcium alone or calcium with vitamin D has an effect on the risk for cancer.

Whereas the health benefits of calcium supplementation are questionable, growing evidence indicates that calcium supplementation may be associated with an increase in the risk for CVD. In a trial of over 1400 women who were randomly assigned to receive calcium citrate 1 g or placebo daily, the risk for the combined endpoint of myocardial infarction, stroke, or sudden death was nearly 50% higher in the calcium group during 5 years of treatment.[5] Although data from the Women's Health Initiative initially pointed to a lack of effect of calcium supplements on the risk for cardiovascular events, a separate analysis found that calcium supplements significantly increased the risk for these events, particularly myocardial infarction.[6,7] In a meta-analysis, the use of calcium supplements vs placebo was associated with a hazard ratio for myocardial infarction of 1.31 (95% CI, 1.02-1.67).[8] There were nonsignificant increases in the risks of stroke and a combined cardiovascular endpoint in women taking calcium vs placebo.

The data regarding any relationship between dietary calcium and the risk for CVD is weaker than that for calcium supplements.[9] However, a recent study found a significant increase in the risk for mortality outcomes associated with calcium consumption among a cohort of 61,000 women who were followed for a median of 19 years.[10] Compared with more modest consumption of dietary calcium, calcium intake of over 1400 mg/day was associated with a hazard ratio of 1.49 (95% CI, 1.09-2.02) for death from CVD, as well as a higher risk for death from any cause (hazard ratio, 1.40; 95% CI, 1.17-1.67).

The potential cardiovascular risk associated with calcium intake is an evolving field of inquiry. The current study uses a large database of older adults to add to the sum of evidence regarding this issue.

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