In mid-2010, news reports responded to a contentious research study in the "British Medical Journal" claiming that supplementation with calcium could increase your risk of heart disease. Although there are some theoretical avenues through which calcium can contribute to heart disease, the study's findings were harshly criticized. Recommendations about calcium intake in the United States remain unchanged.
Calcium's Role in the Body
Calcium is the most abundant mineral in your body. That's because your bones and teeth and, to a lesser extent, your blood and soft tissue are essentially calcium stores. Calcium supports muscle contraction, blood clotting, nerve function, bone formation and a normal heart rate. Having a calcium deficiency puts you at risk of osteoporosis, weight control problems, and, possibly, an abnormal heart rhythm, according to the Office of Dietary Supplements.
The "Shot" Heard Around the World
In July 2010, an international group of medical researchers led by a fellow from the University of Auckland in New Zealand published a controversial meta-analysis. The group concluded that calcium supplements, when taken without vitamin D, are associated with increased risk of myocardial infarction. This is a heart attack and involves damage to the heart muscle tissue because of impeded blood supply. Their results, published in the "British Medical Journal," are based on analysis of 26 previously published clinical trials involving more than 20,000 patients. While the study did not influence recommendations by United States public health officials, it is unknown whether many doctors changed their practices, even though the authors encouraged a "reassessment" of calcium supplementation.
Criticism and Considerations
The Harvard Health Letter put the results of the unnerving study in perspective, noting that almost 30 percent increased risk of cardiovascular disease from calcium supplements could be more practically summed by stating that 5.8 percent of people taking calcium had an adverse heart event compared with 5.5 percent of people who took a placebo. The NIH Office of Dietary Supplements also notes that the review was criticized because none of the studies in the analysis were originally designed to study heart disease and contradictions lay in the fact that the studies found no simultaneous increase in strokes or death. In addition, the studies included people who only took calcium, and not the more common combination of calcium plus vitamin D.
Possibility
The Harvard Health Letter notes that although the evidence is not yet visible in clinical research, it is theoretically conceivable that calcium could play a role in heart disease. Heart attacks occur because your blood vessels get blocked by plaques, which are made up of cholesterol and other materials, and calcium is one of them. However, it is yet unknown if there is a link between any amount of calcium in your blood to heart disease. Calcium could also reduce heart disease by decreasing the absorption of lipids in your intestines, flushing more of them out and lowering the cholesterol in your blood. The Office of Dietary Supplements points to a mixed set of results from research, showing a positive effect and showing no effect; the totality of the evidence does not support a link between calcium and cardiovascular disease risk.
Current Recommendations on Calcium Intake
Children ages 1 to 3 need roughly 700 mg of calcium daily, according to the Institute of Medicine. Then, until age 18, they need 1,300 mg. Adults need 1,000 mg. However, around age 50, women need 1,200 mg; this recommendation applies to men when they reach age 70. In addition, teenage pregnant and nursing mothers have additional calcium needs. Cheddar cheese, milk and yogurt are good sources of calcium; nondairy sources include sardines and vegetables like Chinese cabbage, kale and broccoli.
References
- "British Medical Journal"; Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis; Mark J. Bolland et al.; July 29, 2010
- NIH Office of Dietary Supplements; Dietary Supplement Fact Sheet: Calcium
- "Harvard Health Letter"; Could too much calcium cause heart disease? P.J. Skerrett; August 10, 2010
- Linus Pauling Institute; Calcium; Jane Higdon; April 2003
- Institute of Medicine: Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Vitamins
- "Annals of Internal Medicine"; Systematic Review: Vitamin D and Cardiometabolic Outcomes; Anastassios G. Pittas et al.; March 2, 2010
