Taking calcium supplements doubles the risk of heart attacks, according to a controversial new study by Swiss scientists.
University of Zurich researchers found that people who take the pills are 86 percent more likely to have a heart attack than those who do not, after studying data on 24,000 German men and women aged 35 to 64, over 11 years.
The risk more than doubled for people taking only calcium supplements, the researchers said.
Their findings, published in the journal Heart, could not show cause and effect, but advised that the supplements should be "taken with caution."
"It is now becoming clear that taking this micronutrient in one or two daily [doses] is not natural, in that it does not reproduce the same metabolic effects as calcium in food," the study authors wrote.
While dietary calcium is absorbed by the body slowly throughout the day, calcium supplements -- which are often prescribed to elderly people and postmenopausal women to prevent bone-thinning -- are more harmful because they cause calcium levels in the blood to soar, producing a "flooding" effect, the scientists said.
"We should return to seeing calcium as an important component of a balanced diet, and not as a low cost panacea to the universal problem of postmenopausal bone loss," the researchers concluded.
The participants in the Swiss study had taken part in the European Prospective Investigation into Cancer and Nutrition, which involved recording their diet and vitamin and supplement intake.
Dr. Taylor Wallace, senior director of scientific and regulatory affairs for the US Council for Responsible Nutrition, disputed the findings, which he pointed out contradicted with previous studies.
"Our advice is for consumers to be aware of how much calcium they get from their diet, supplement with calcium if needed, and check with their doctor or other healthcare practitioner to determine their own personal needs," Wallace said.