CALCIUM AND HEART WOES
In this meta-analysis of 15 randomized blinded placebo-controlled trials, Dr. Mark Bolland from the University of Auckland in New Zealand and colleagues evaluated calcium supplement use (at least 500 mg daily) in more than 12,000 patients older than 40 years of age. The findings were surprising: The pooled results linked calcium supplement intake to a significant 30% increased risk for heart attack. A tendency to increased risk for stroke and sudden death was also seen, but this result was not significant. Of note, cardiovascular outcomes were not a primary endpoint in any of the individual trials. Proposed mechanisms for the higher risk include increased blood coagulability and decreased blood vessel compliance due to calcium buildup in the arterial wall. On the basis of these findings, the authors postulate that treating 1000 people with calcium for five years would prevent 26 fractures but cause an additional 14 heart attacks. This is not the first time that Dr. Bolland has studied calcium intake and cardiovascular outcomes. Two years ago, results of a randomized placebo-controlled study of 1471 postmenopausal women were published that linked calcium supplements with greater cardiovascular risk. That 2008 study by Bolland and colleagues was included in their 2010 meta-analysis.
Bolland MJ, Avenell A, Baron J, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010; 341:c3691.
COMMENT
Now with this emergence of the safety concern regarding supplemental calcium, which has come soon after the declaration of an increased risk of cancer esophagus(BMJ Sep 10) and atypical fractures (FDA Announcements Oct 10,J Bone Miner. Res.Sep.10) with the use of bisphosphonates, I think we are left with a good and nutritious diet only. Probably the age-old advice of grandma was the best, to have a good portion of milk in the daily diet.
Though so far I have not changed my prescription habits, each time I write calcium supplement I am forced to “think”.