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If you live in the United States, you have almost certainly heard the advertising slogan, "Milk does a body good." One of the reasons millions believe milk does a body good is its content of calcium needed for healthy bones, but not everyone likes to drink (or can drink) milk on a daily basis.
To fill the gap, the supplements industry has promoted calcium supplements for bone health for over 20 years. Unfortunately for men, a new study sponsored by the NIH (National Institutes of Health) and the AARP (American Association of Retired Persons) finds that taking more than 1,000 mg of calcium per day raises the risk of death from cardiovascular disease in men by approximately 20%.
Is Calcium a Killer?
The NIH-AARP study, published in the Journal of the American Medical Association 4 February 2012, reported a study of 388,229 American men and women aged 50 to 71 who were first contacted in 1995 and 1996. These Americans were asked whether they took calcium supplements, and if they did, how much. Then researchers followed the AARP volunteers for the next 12 years, noting deaths recorded in the National Death Index.
Among the women in the study, taking more than 1,000 mg of calcium supplements per day was associated with a 5% greater risk of dying of heart disease, a 6% greater risk of dying of other kinds of chronic cardiovascular disease, or an 8% greater risk of dying from stroke. In women, however, the relationship between calcium and cardiovascular disease was only a trend. It was not statistically significant. (That is, the researchers could not state with 95% certainty that there wasn't an off chance that women's taking calcium's supplements actually lowered the risk of heart disease).
Among the men in the study, taking more than 1,000 mg of calcium supplements per day was associated with a 19% greater risk of dying of heart disease, a 20% greater risk of dying of other kinds of chronic cardiovascular disease, and a 14% greater risk of dying from stroke. Only the 19% greater risk of dying from heart disease, however, was statistically significant.
The study also made several interesting findings that didn't make most of the news reports about it.
The men at greater risk of death from heart disease, the researchers found, were less likely to smoke, more likely to exercise, better educated, and ate more fruits and vegetables.
Assuming that not smoking, exercising more, knowing more, and eating more fruits and vegetables don't cause heart disease, it appears that taking calcium cancels out other healthy lifestyle choices.
Only Supplements Seem to Make a Difference
It is worth repeating that this study did not find that consuming high-calcium foods such as milk, cheese, yogurt, fish, and leafy green vegetables was not associated with greater risk of any kind of cardiovascular disease. Only supplements seem to make a difference.
And it is also helpful to understand that previous studies have not suggested this problem. A study published in the same journal in 1996, for example, found that taking calcium supplements slightly lowered blood pressure (systolic blood pressure, the first number, but not diastolic blood pressure, the second number). And a study published just a few months earlier in the American Journal of Medicine just a few months earlier reported that the link between calcium supplements and heart disease risk was unclear.