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Calcium supplementation may raise risk for CAC
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High overall intake of calcium was linked to lower risk for incident atherosclerosis in a new analysis of the MESA cohort, but use of calcium supplements was linked to elevated risk for development of coronary artery calcium.
The researchers analyzed 5,448 participants (52% women) from the MESA cohort study aged 45 to 84 years without CVD at baseline.
At baseline, participants were stratified into quintiles by total calcium intake from diet and from calcium supplements.
All participants had coronary artery calcium (CAC) measured by CT at baseline and 2,742 had it measured again at 10 years.
Mean calcium intake was 313.3 mg per day in the lowest quintile, 540.3 mg per day in the second-lowest, 783 mg per day in the middle quintile, 1,168.9 mg per day in the second-highest and 2,157.4 mg per day in the highest quintile, with women having higher intake than men, John J.B. Anderson, PhD, from the department of nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, and colleagues reported.
After adjustment for potential confounders, among those without CAC at baseline, the risk for developing CAC at 10 years declined with increasing quintile of overall calcium intake.
Compared with those in the lowest quintile, the RRs for incident CAC at 10 years were 0.95 (95% CI, 0.79-1.14) in the second-lowest, 1.02 (95% CI, 0.85-1.23) in the middle, 0.86 (95% CI, 0.69-1.05) in the second-highest and 0.73 (95% CI, 0.57-0.93) in the highest, according to the researchers.
However, after adjusting for total calcium intake, greater use of calcium supplements was associated with increased risk for development of CAC (RR = 1.22; 95% CI, 1.07-1.39), they found.
There was no relationship between calcium intake and changes in CAC in those who had CAC greater than 0 at baseline, Anderson and colleagues wrote.
“These results suggest that any protective association of calcium intake and incident CAC occurs in the participants with high dietary calcium intake (excluding supplemental calcium), which could be a proxy for overall healthier diets,” they wrote. “The relationship between calcium intake and CVD risk is complex and appears to depend on the source of calcium intake.” – by Erik Swain
Disclosure: One researcher reports receiving an honorarium from Siemens Diagnostics for work unrelated to the present study.
Perspective
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Khaled A. Dajani, MD, MBA, FACC
What this study adds to the knowledge base is that some people take calcium supplements to treat and prevent bone diseases like osteoporosis, and the calcium in these supplements could make its way into the fatty plaques of your arteries and cause atherosclerosis. There has been controversy about whether there is an increased risk for MI or stroke and other CVDs from taking calcium supplements, and this study shows that there may be higher risk in people who take calcium supplements vs. those who consume calcium intake naturally through sources like milk, cheese or other calcium-rich foods.
It is unclear at this point why dietary calcium appears to be beneficial for the development of CAC and the opposite seems to be true for calcium supplements, but it may have to do with the makeup of the calcium supplements. Supplements may have additional salts that are attached to the calcium that may be attracted to the fatty plaques inside the coronary arteries.
This issue should be discussed on an individual basis between the patients and the physician to determine the best amount of calcium in the diet, the best way to get that amount, and whether to take supplements or increase natural intake.
People should not be alarmed over the findings of this study. This was an observational study with many confounding factors. People should not be discouraged about taking calcium in the diet — especially those patients who are at risk for osteoporosis.
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