Is Calcium Bad for the Heart?

The calcium controversy helps draw attention to bone health. That’s good! Lots of media over a study with lots of flaws and a “trivial result.”
Here’s my opinion on the meta-analysis of calcium supplements and risk of heart attacks and cardiovascular events released yesterday on BMJ online first.

Heart disease was not the focus of the individual studies. The analysis included almost 12,000 subjects from studies focused on bone density, fractures or colon polyps. The randomization process done for these trials to make the groups equal is based on those problems not cardiovascular disease. They have only data on cardiovascular risks (high blood pressure, lipid levels, diabetes, history of angina, heart attacks or strokes) for less than a quarter of the subjects. Therefore, you do not know whether the calcium and placebo groups started out with equal, higher, or lower risks of cardiovascular disease. A comparison is made of cardiovascular events without knowledge of baseline risks.

Daily calcium is higher than recommended. The total calcium intake of the combination of dietary sources and supplements is 1000 milligrams (mg) above the recommended total intake. The average total intake is over 2200 mg daily. The total calcium recommendation for adults age 19 to 50 is 1000 mg and over 50 is 1200 mg daily.

Vitamin D is essential. This analysis did not include any studies using vitamin D supplementation, which is the current standard of care. Low vitamin D with higher levels of parathyroid hormone are associated with cardiovascular events in the general population. The vitamin D status of the subjects is not known.

The risk of heart attack was low in both groups. Calcium supplements increased risk of heart attack by 30 per cent but not stroke or death. The risk of heart attacks was only 2.7% in the calcium group versus 2.2% in the placebo. The rate of heart attacks in similar age individuals (average age 72) or “standardized rate” is not given for comparison. You don’t know if the 2.7% is above or below the population rate. Also, the heart attacks were not “authenticated” by medical records.

Is it a blood calcium problem? The paper does not go into mechanism but assumes their observation is based on raising blood calcium levels and promoting calcification of blood vessels. They do not explain the inconsistency of results–a small increase of heart attacks, not stroke or death. Abnormalities in mineral metabolism are associated with cardiovascular disease. These mechanisms are not related to increase in calcium but protein regulators of vascular calcification.
Bottom line. Based on the results of this study, you should not stop your calcium supplements. You should add up your diet sources and only take supplements to reach 1000 to 1200 mg total a day. In addition, make sure you are taking sufficient vitamin D. A vitamin D blood level over 30 ng/ml is necessary for efficient absorption of calcium.

-Diane L. Schneider, MD
Source: Bolland MJ et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010 Jul 29;341:c3691

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