A new study adds to evidence that calcium supplements — but not calcium from food — might be bad for your heart.
At the same time, a second study shows Americans still have faith in their supplements. About half take supplements of some sort, despite dozens of studies showing they do not help most healthy people at all and can often be harmful.
The new research builds an even stronger case against calcium pills.
People who took calcium pills were about 22 percent more likely to develop dangerous buildups called plaque in their arteries than people who did not take them, the new study showed.
But people who also ate a lot of calcium in food seemed to be protected, the team at Johns Hopkins University found.
“Based on this evidence, we can tell our patients that there doesn’t seem to be any harm in eating a heart-healthy diet that includes calcium-rich foods, and it may even be beneficial for the heart,” Dr. Erin Michos, an expert in heart disease prevention who helped lead the study, said in a statement.
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“But patients should really discuss any plan to take calcium supplements with their doctor to sort out a proper dosage or whether they even need them.”
The findings, published Tuesday in the Journal of the American Heart Association, backs up what experts already know about calcium supplements. Other studies have also shown the pills might not strengthen bones and might just send calcium straight to the blood vessels instead.
It’s not clear why.
“There is clearly something different in how the body uses and responds to supplements versus intake through diet that makes it riskier,” said John Anderson, a nutrition professor at the University of North Carolina at Chapel Hill who worked on the study.
“It could be that supplements contain calcium salts, or it could be from taking a large dose all at once that the body is unable to process.”
For the study, the team looked at 2,700 people taking part in a larger survey. They had filled out questionnaires in 2000 and got CT scans — a type of souped-up x-ray — in 2000 and again in 2010.
These CT scans can show whether calcium-heavy deposits are building up in the arteries.
Those who ate more than 1,400 milligrams of calcium a day were 27 percent less likely to have this buildup than the others, the team found.
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But when they looked at the source of calcium, they found those who took supplements were more likely to develop the blockages.
The Council for Responsible Nutrition, a lobby group for the supplement industry, said in a statement that the findings showed calcium supplements are safe. It did not explain why it came to that conclusion.
Federal data show that about half of Americans take calcium supplements.
In 2012, the U.S. Preventive Services Task Force issued new recommendations saying there's not enough evidence to support the use of calcium or vitamin D supplements, and recommending against it in some cases.
Women over 50 are advised to get 1,200 mg of calcium a day and women under 50 are advised to get 1,000 mg a day. Men are advised to get 1,000 mg a day although men over 70 are supposed to get 1,200 mg.
Dairy products are rich in calcium but so are leafy green vegetables, fortified milks such as soymilk and some juices and breakfast cereals.
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No better than a placebo?
Another study released Tuesday in the Journal of the American Medical Association showed that just over 50 percent of Americans take vitamins or supplements of some sort.
Most are doing it on their own, Elizabeth Kantor of Memorial Sloan Kettering Cancer Center in New York, and colleagues found.
“Although often used with an intention of improving or maintaining health, it was estimated that in 2007- 2010 only 23 percent of all supplement products were used at the recommendation of a health care provider,” they wrote.
“Why would consumers continue to use supplements after high-quality trials found many of these products to be no more effective than placebos?” Dr. Pieter Cohen of Harvard Medical School asked in a commentary.
“One factor may simply be that consumers are not aware of these negative results, and so continue to use the products they have been using for years,” he said.
But some may not believe medical science, while others may be swayed by the heavy advertising of the $32 billion supplement industry, which is only lightly regulated, Cohen said.