Women eating a high-calcium diet and taking calcium supplements adding up to more than 1,400 milligrams a day may be running nearly twice the risk of dying from heart disease, a large Swedish study suggests.
Both men and women take calcium supplements to prevent bone loss. The new findings come on the heels of another recent study that found a similar increased risk of death related to calcium intake among men.
"Many older adults increase dietary intake of calcium or take calcium supplements to prevent bone loss and there had been speculation that increased calcium intake with or without vitamin D could improve cardiovascular health," said Dr. Gregg Fonarow, an American Heart Association spokesman who wasn't involved in the study.
SPECIAL: These 4 Things Happen Right Before a Heart Attack — Read More.
However, a number of recent studies have suggested that higher dietary intake or calcium supplementation may not only not improve cardiovascular health -- they may be associated with increased risk for cardiovascular events and mortality, said Fonarow, a professor of cardiology at University of California, Los Angeles.
The new report was published in the Feb. 12 online edition of the BMJ.
To see if calcium supplements raised the risk of dying from heart disease, a team led by Dr. Karl Michaelsson, a clinical professor in the department of orthopedic surgical sciences at Uppsala University in Sweden, analyzed data collected on more than 61,000 women enrolled in a study on mammograms.
Over 19 years of follow-up, nearly 12,000 women died -- almost 4,000 dying from cardiovascular disease, about 1,900 from heart disease and 1,100 from stroke, the researchers found.
The highest rates of death were seen among women whose calcium intake was higher than 1,400 milligrams a day, the researchers noted. On the other hand, women who took less than 600 milligrams of calcium a day were also at an increased risk of death.
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.
SPECIAL: These 4 Things Happen Right Before a Heart Attack — Read More.
"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 said: "While further studies are needed, calcium supplements should be used only after careful consideration of whether the potential benefits in terms of bone health outweigh the potential cardiovascular risks."