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Calcium Supplements and Heart Disease, New Information

Tuesday, May 29, 2012 // Uncategorized

Health doesn’t come in a pill revisited.

Controversy has been brewing since a study was published suggesting a link between heart attack risk and the use of calcium supplements in the British Medical Journal about a year ago.  Here is a recent Journal Watch commentary on an article in Heart.  It suggests that dietary calcium may be inversely related to heart attack risk whereas calcium supplementation is related to increased heart attack risk.  Bottom line:  It continues to appear that nutrients in one’s diet have a beneficial impact on health, but supplements do not.  In fact, they may have an adverse effect on health. 

Calcium Supplements Might Increase MI Risk
Use of calcium supplements is associated with a near doubling of risk for myocardial infarction, but calcium intake through diet does not confer increased risk, according to a study in Heart.
German researchers analyzed data from nearly 24,000 residents aged 35 to 64 who completed questionnaires about diet and supplement use. After 11 years’ follow-up, some 350 people had experienced an MI. People who were in the third quartile of dietary calcium consumption had a lower MI risk, relative to those in the lowest quartile (hazard ratio, 0.69). However, those who took calcium supplements had increased MI risk, compared with nonusers (HR, 1.86).
The authors conclude that calcium supplementation “should be taken with caution.” Editorialists note: “The evidence is … becoming steadily stronger that it is not safe, nor is it particularly effective. … We should return to seeing calcium as an important component of a balanced diet and not as a low-cost panacea to the universal problem of postmenopausal bone loss.”

Here is the abstract from Heart.

Abstract

Background It has been suggested that a higher calcium intake might favourably modify cardiovascular risk factors. However, findings of an ultimately decreased risk of cardiovascular disease (CVD) are limited. Instead, recent evidence warns that taking calcium supplements might increase myocardial infarction (MI) risk.

Objective To prospectively evaluate the associations of dietary calcium intake and calcium supplementation with MI and stroke risk and overall CVD mortality.

Methods Data from 23 980 Heidelberg cohort participants of the European Prospective Investigation into Cancer and Nutrition study, aged 35–64 years and free of major CVD events at recruitment, were analysed. Multivariate Cox regression models were used to estimate HRs and 95% CIs.

Results After an average follow-up time of 11 years, 354 MI and 260 stroke cases and 267 CVD deaths were documented. Compared with the lowest quartile, the third quartile of total dietary and dairy calcium intake had a significantly reduced MI risk, with a HR of 0.69 (95% CI 0.50 to 0.94) and 0.68 (95% CI 0.50 to 0.93), respectively. Associations for stroke risk and CVD mortality were overall null. In comparison with non-users of any supplements, users of calcium supplements had a statistically significantly increased MI risk (HR=1.86; 95% CI 1.17 to 2.96), which was more pronounced for calcium supplement only users (HR=2.39; 95% CI 1.12 to 5.12).

Conclusions Increasing calcium intake from diet might not confer significant cardiovascular benefits, while calcium supplements, which might raise MI risk, should be taken with caution.

Here is the Journal Watch summary on the BMJ article:

Calcium, With or Without Vitamin D, Raises Risk for Adverse Cardiovascular Events

Vascular calcification is one proposed mechanism.

A recent meta-analysis showed that calcium supplementation without vitamin D elevates cardiovascular (CV) risk (JW Gen Med Aug 31 2010). However, whether calcium and vitamin D taken together elevate CV risk is unclear. Although the Women’s Health Initiative (WHI) previously reported that calcium and vitamin D supplements taken together did not elevate CV risk, about half the 36,000 participants were taking nonprotocol calcium and vitamin D at randomization — potentially obscuring the association. To determine whether calcium and vitamin D taken together elevate CV risk, investigators reanalyzed WHI data according to personal use of calcium and incorporated these data in a meta-analysis of eight additional studies.

In the reanalysis of WHI data, women who did not report baseline calcium use who were randomized to daily calcium (1 g) and vitamin D (400 IU) had significantly elevated risks for myocardial infarction, MI or revascularization, and MI or stroke (hazard ratio, 1.2 for each outcome), compared with placebo recipients. In contrast, users of calcium at baseline who were randomized to calcium and vitamin D did not have excess CV risk compared with placebo recipients.

In a meta-analysis of three randomized trials with 20,000 participants, calcium and vitamin D supplementation raised risks for MI, stroke, and a composite of MI or stroke, compared with placebo (relative risk, 1.2 for each outcome). A meta-analysis of nine trials that involved 28,000 participants showed that calcium or calcium and vitamin D supplementation significantly raised risks for MI and a composite of MI or stroke compared with placebo (RR, 1.2 for each outcome). The average duration of the trials was about 6 years.

Comment: These results suggest that calcium supplements, with or without vitamin D, raise risk for adverse CV events. The authors note “calcium supplements acutely increase serum calcium concentration . . . an effect that is sustained during long term treatment, as evidenced by lower levels of parathyroid hormone” and might promote vascular calcification. That baseline users of calcium in the WHI study who were randomized to calcium and vitamin D did not have excess CV risk suggests a dose-response relation does not exist. The authors speculate “the abrupt change in plasma calcium after supplement ingestion” rather than total calcium load causes the adverse effect. What should clinicians do until these results are confirmed or refuted by additional research? One approach would be to advise patients to increase calcium intake through food sources (e.g., milk products), as the aforementioned studies say nothing about this type of calcium intake. Another approach would be to avoid calcium supplementation in patients at high CV risk.

Paul S. Mueller, MD, MPH, FACP

Published in Journal Watch General Medicine May 12, 2011

Citation(s):

Bolland MJ et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: Reanalysis of the Women’s Health Initiative limited access dataset and meta-analysis. BMJ 2011 Apr 19; 342:d2040. (http://dx.doi.org/10.1136/bmj.d2040)

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