Dear Doctor: Calcium is frequently recommended to reduce the risk of bone fractures in the elderly, but I've read that calcium builds in the arteries and heart. So what choice do women have -- die of a hip fracture or die of a heart attack? Personally, I don't know which would be better.
Dear Reader: You highlight an interesting issue. There is no doubt that calcium is beneficial for bones, with supplementation improving bone density and -- at 500 to 1,200 milligrams per day -- leading to a 9 to 19 percent decrease in the rate of hip fractures. But it's true that supplements may have risks as well.
First, for women over 50, supplementation with 1,000 mg of calcium and 400 IU of vitamin D leads to a 17 percent increased risk of kidney stones. Second, calcium supplementation for people with kidney dysfunction or those on dialysis causes increased calcification of blood vessels and a greater risk of heart attacks and strokes.
A 2008 study of 1,471 postmenopausal women in New Zealand compared the effects of 1,000 mg of calcium citrate to those of a placebo. In five years of follow-up, women who took the calcium had an improvement in the ratio of their good to bad cholesterol (HDL/LDL). However, after 2 1/2 years, the group that took the calcium started to show an increased risk of heart attacks; after five years, they had a 49 percent increased risk.
Then there was a 2010 British Medical Journal study that combined data from 11 studies in which women took elemental calcium supplements of 500 mg or more. The studies, which evaluated fracture risk and bone density, weren't intended to assess heart attack and stroke risk, but researchers did gather data on the conditions. In total, the group that took calcium had a 27 percent increased risk of heart attacks and a 12 percent higher risk (not considered statistically significant) of strokes.
In 2011, the same authors tackled data from the Women's Health Initiative (WHI) study in which 36,282 women took 1,000 mg of calcium and 400 IU of vitamin D or a placebo for seven years. The initial study did not reveal an increase in heart attacks among women taking calcium supplements, but as it turned out, 54 percent were taking additional calcium beyond the supplements that were part of the trial. Noting this, the authors of the study compared their data with data from the 46 percent who were not taking additional calcium. They found that the group taking the 1,000 mg of calcium had a 16 percent increase in the rate of heart attacks.
Other grouped studies (using the initial data of the WHI study) have not shown this degree of risk with calcium supplementation.
Confusing, isn't it? Here's the take-home message: If you're otherwise healthy, taking up to 1,000 mg of calcium supplements may be safe. But if you have risk factors for a heart attack or stroke, such as a history of smoking, diabetes, kidney dysfunction or a significant family history of heart disease, I would avoid large doses of calcium and would, in fact, limit calcium supplement intake to no more than 500 mg per day. It's all about balancing bone health with overall health.