Women who use calcium supplements may be at an increased risk of heart problems in later life according to a recent New Zealand study published in the British Medical Journal this month.
Researchers from the Department of Medicine at the University of Auckland followed 1471 healthy post-menopausal women, all over the age of 55, for a period of five years. Half the group took a calcium supplement which contained 1 gram of calcium while the other half received a placebo.
During the study, 31 of the women receiving the calcium supplements suffered at least one myocardial infarction (heart attack) compared to just 21 women in the placebo group. After adjusting the results for potential confounding factors, the researchers found that women taking the calcium supplements were at 2.12 times the risk of suffering a heart attack compared to the placebo group.
Furthermore, the group receiving the calcium supplementation were at a 47% higher risk of having one of three “adverse cardiovascular events” which was defined as a heart attack, stroke, or sudden death.
The cumulative risks of suffering a heart attack for the calcium group and the placebo group over the 5 year study are presented in the graph below.
The findings of this study are in contrast to recent studies which have suggested calcium may have a protective effect on the heart.
The researchers admit the results may not be conclusive as the results become statistically insignificant once data from hospital admissions and unreported deaths that were not originally included in the study were factored in. When this data was included the relative risk of heart attack in the calcium supplemented group dropped to 1.49 and the relative risk of the combination of heart attack, stroke, or sudden death dropped to 1.21 times higher than the placebo group.
The authors concluded: “The present data do not permit definitive conclusions to be reached in this regard but do flag cardiac health as an area of concern in relation to calcium use.”
Calcium supplementation leads to a short term increase in blood calcium levels which some scientists believe may increase the rate of calcium deposition (calcification) of the arteries. On the other hand, calcium supplementation has been found to increase the ratio of HDL to LDL cholesterol which has a positive effect on heart health.
Further research will likely be conducted to determine whether there is a real risk of cardiac problems from taken high doses of calcium. In the mean time, doctors suggest that people currently taking calcium supplements, particularly women, should continue to do so as the beneficial effects of the mineral, such as increased bone density likely outweigh any potential negative effects.
Whenever possible, people should try to get their recommended daily intake (RDI) of calcium from food-based sources rather than relying on supplements alone. Good sources of calcium include dairy products, tofu, beans, almonds, oats, sardines, and salmon. The recommended daily intake of calcium in the United States is 1 gram for men aged under 65 and women under 50. The RDI increases to 1.5 grams for men over 65 and women over 50.
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