THE QUESTION Although calcium has proven benefits, might too much of it cause problems, particularly for the heart?
THIS STUDY analyzed data on 61,433 women, most in their mid-50s at the start of the study. Over roughly the next two decades, calcium consumption from both dietary sources and supplements was calculated periodically. In that time, 11,944 of the women died, including 3,862 from cardiovascular disease, 1,932 from ischemic heart disease (also called coronary artery disease) and 1,100 from a stroke. Women who took in the most calcium — more than 1,400 milligrams daily — were more than twice as likely to have died from heart disease and about 50 percent more likely to have died from cardiovascular disease as women whose daily calcium consumption was in the 600- to 999-mg range. Taking calcium supplements did not seem to affect the results except among those with the highest calcium intake; for the women in that group, those whose calcium came from dietary sources plus supplements had a higher death rate than those who did not take supplements. Daily calcium consumption of 600 to 1,400 mg did not increase the death rate, but women whose calcium intake was low — less than 600 mg a day — also had a somewhat higher death rate. No link was found between calcium consumption and death from a stroke.
WHO MAY BE AFFECTED? Middle-age and older women, who are encouraged to take 1,200 milligrams of calcium daily. Calcium is found naturally in milk, cheese, yogurt, broccoli, salmon and almonds, among other foods, and is often added to cereals and fruit juices. Known for its role in building and strengthening bones and teeth, calcium also helps muscles contract, helps nerves function properly and helps regulate heart rhythm and blood pressure. Some believe that excess calcium can accumulate in the arteries over time.
CAVEATS Data on calcium consumption came from the women’s responses on questionnaires. Whether the findings apply to men was not tested.
FIND THIS STUDY Feb. 13 online issue of BMJ.
The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.