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Women who hope to prevent osteoporosis by taking calcium supplements and vitamin D are at increased risk for heart attack or stroke, according to a report published in BMJ. The finding suggests that calcium supplementation may not be as safe as conventional wisdom once believed.
Calcium Supplements Increase Heart Attack and Stroke Risk
Researchers re-analyzed data from the Women's Health Initiative Calcium/Vitamin D Supplementation Study (WHI CaD Study) as well as examining data from eight other studies for a complex meta-analysis of the effects of personal calcium supplement use on cardiovascular risk.
The WHI CaD Study involved 36,282 postmenopausal women who participated in a seven year long randomized placebo controlled trial that compared vitamin D and calcium. Part of the WHI CaD Study's objectives was to ascertain the effects of long term calcium supplementation on hip bone density i.e. reducing osteoporosis risk.
After scientists carefully re-analyzed data from WHI CaD and eight other studies they concluded that calcium supplementation increases heart attack risk by 25% - 30% and stroke by 15% - 20%.
In the study published in the British Medical Journal, primary research investigator Mark J Bolland and his team said that although the increase was modest"...because of the widespread use of calcium supplements either alone or with vitamin D, even small increases in cardiovascular disease incidence may translate to a substantial population burden of disease, particularly in older age groups." In other words, the health of older women could be compromised by calcium supplementation.
Does Calcium Supplementation Prevent Osteoporosis Risk?
In 2006 the National Institutes of Health published a press release about the findings of the WHI CaD Study stating that "calcium and vitamin D supplementation in healthy postmenopausal women provide a modest benefit in preserving bone mass and prevent hip fractures in certain groups including older women..." The key point is "healthy postmenopausal women".
Interestingly, the results of a population based cohort of Swedish women who took dietary calcium published in the British Medical Journal earlier this year concluded that beyond a certain point, dietary calcium did not further reduce fracture risk or osteoporosis.
These studies seem to come to contradictory conclusions regarding the benefits of calcium for osteoporosis prevention. At this point, some people are asking themselves what does calcium have to do with the heart? I'll briefly discuss that in the next section.
Role Of Calcium In The Body
Calcium is an important biomineral and is involved in a multitude of biological functions including:
- signal transduction across cellular membranes
- muscular contraction (smooth, cardiac and skeletal)
- tissue mineralization (e.g. bone and teeth)
- enzymatic reactions
- blood clotting
Bones incorporate calcium into their matrices thus allowing the tissues to become denser, stronger and thereby more resistant to fractures. Menstruating women produce estrogen, this steroid hormone also helps maintain strong bones.
When a woman enters menopause, her estrogen levels drop off which can lead to weakened bones. Thus health care professionals may advise women to take calcium supplements to help supply bones with this necessary mineral.
In addition to calcium, some women also take vitamin D, because of its role in strengthening bone tissue. But calcium also interacts with a special form of vitamin D which is known as vitamin D3 or cholecalciferol. When the body has too much calcium or vitamin D3 it can create problems for the heart. Thus it becomes much easier to see why people should carefully weigh the costs versus benefits of taking calcium supplements.
What Does This Information Mean To You?
Calcium has many physiological uses such as strong bones and muscle contractions. The best sources are milk, beans, dark green vegetables and nuts. Calcium supplements are often taken by those who don't get enough dietary calcium but excess calcium can increase cardiovascular risk in susceptible populations. Thus, people should have a sit down with their doctor to decide if calcium supplementation is the best thing for maintaining their health and wellbeing.
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Bolland, M. J. 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;342:d2040
Warensjo, E. et al. Dietary calcium intake and risk of fracture and osteoporosis: prospective longitudinal cohort study. BMJ 2011;342d:1473
NIH News http://www.nhlbi.nih.gov/new/press/06-02-15.htm
"Study: Calcium Supplements Can Cause Heart Attacks" copyright 2011 Living Fit, Healthy and Happy(SM). All Rights Reserved.