Moreover, women taking 1,400 milligrams of calcium a day and also using a supplement had even a higher risk of dying than women not using supplements, Michaelsson's group found.
All in all, women getting more than 1,400 milligrams of calcium a day were more than twice as likely to die than women getting 600 to 999 milligrams a day, the researchers said.
The U.S. Office of Dietary Supplements recommends 1,000 to 1,200 milligrams of calcium a day for most adults.
According to the study authors, diets very low or very high in calcium can override normal control by the body, causing changes in blood levels of calcium.
Rather than worry about increasing calcium intake of those getting enough through their diet, emphasis should be placed on people with a low intake of calcium, the authors suggest.
Taylor Wallace, a representative of the supplement industry, faults this study because, he said, it was not specifically meant to address calcium supplements and heart disease.
"We are comparing apples and oranges," said Wallace, who is senior director for Scientific & Regulatory Affairs at the Council for Responsible Nutrition. He noted that in the new study, the data that researchers used to draw their conclusions looked at diet and cancer, not whether calcium supplements were bad for the heart.
"Still, there is not a single human cause-and-effect study that demonstrates a hazard for calcium either from the diet or supplements and cardiovascular disease," he said.
Although the new study tied total calcium intake to increased risk of death from heart disease in women, it didn't establish a cause-and-effect relationship.
Wallace did say it's important to know how much calcium a person is getting from diet and supplements. "It is important to talk with your doctor to make sure you are getting the right amount for you," he said.
For his part, heart association spokesman Fonarow
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