Calcium supplements have long been advocated as a way to reduce the risk of osteoporosis. Millions of American women and many men have been taking calcium supplements for many years hopeful that they will cut their risk of osteoporotic fractures.
While the bulk of the data suggests calcium supplements are at least marginally beneficial at maintaining bone density in people who are consuming a typical modern diet, this benefit is modest at best.1 The safety of calcium supplements for women has been largely taken for granted except for minor side effects such as constipation. In men there is also concern calcium supplements may heighten the risk of prostate cancer.
However, data have been accumulating over the last several years linking the use of calcium supplements with calcification of arteries and an increased risk of cardiovascular disease and death.
It is now fairly well established that calcium supplements increase the calcification of arteries and increase the risk total and cardiovascular deaths in patients with failing and failed kidneys.2,3,4 Renal patients may be at an even greater risk from calcium supplements than people with normal renal function. As a result of their limited ability to clear excess calcium, supplements may be more likely to promote arterial calcification and cardiovascular events.
To further evaluate whether or not calcium supplementation might increase the risk of cardiovascular events Dr. Ian Reid and colleagues conducted a meta-analysis of 15 randomized controlled trials that monitored the number of cardiovascular events including heart attacks over an average of 3.6 years.
Dr. Reid excluded trials that included vitamin D with the calcium supplement as in such trials the known benefit of extra vitamin D could mask a possible harmful effect from the calcium supplement.
Dr. Reid’s group observed about a 30% significant increased risk of having a heart attack in those taking calcium supplements compared to those taking a placebo. They also noted that the risk of heart attack increased more when higher doses of calcium supplement were taken. The increased risk of heart attack was independent of age, gender or the type of calcium supplement taken. The data also showed a 9% increased risk of death and more strokes in those taking the calcium supplements relative to the placebo but these increases did not reach statistical significance.5
Osteoporosis, like other all too common degenerative diseases seen in modern societies can better be reduced with a diet low in salt, animal fats, and refined carbohydrates but high in fruits, vegetables, with modest amounts of nonfat dairy products or fortified soymilk. Adequate stores of vitamin D should be assured by routine blood testing for 25-OH D and supplements of vitamin D in those whose diet and sun exposure fail to maintain healthy tissue levels. In addition regular exercise and especially resistance training should be encouraged. These measures would not only do far more to reduce the risk of osteoporosis but also significantly cut the risk of cardiovascular disease.
Bottom Line: It now appears that for most women and the vast majority of men that whatever modest benefit there may be from taking calcium supplements on bone health those benefits are likely outweighed by an even greater increased risk of more cardiovascular events. Health professionals should discourage the routine use of calcium supplements and instead encourage the adoption of a healthier diet and resistance exercise program that can reduce the risk of both cardiovascular disease and osteoporosis.
By James J. Kenney, PhD, RD, FACN
1. Am J Clin Nutr 2007;86:1780
2. N Engl J Med 2000;342:1478,
3. Kidney Int 2007;72:1255,
4. Kidney Int 2007;71:438
5. British Medical Journal 2010;341:c3691doi:101136.c3691
For more information on osteoporosis, including a summary of research, visit foodandhealth.com and click on CPE courses in the top right - in the blue panel. On the CPE course page you can read Dr. Kenney’s paper on diet and osteoporosis.
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.