Calcium supplements did not protect pregnant women from bone loss. This new study comes on the heels of a controversial analysis showing that calcium pills increased the risk of heart attacks among older people. Although the evidence that calcium supplementation strengthens bones is modest, tens of millions of women have been popping down calcium in the belief that it would protect them against osteoporosis without negative consequences. The recent analysis in the journal BMJ suggests that assumption may not be valid.
The latest challenge to calcium’s benefits comes from the Gambia. Researchers randomly assigned women to take either 1500 mg of calcium carbonate or a placebo daily during pregnancy. The supplements were continued up to delivery. These women normally had low levels of calcium in their diets, so the scientists expected that the supplements would protect them from bone loss. Pregnancy puts extra demands on calcium stores to help build new bones in the baby. Contrary to expectation, however, the women who got extra calcium had lower bone mineral content than those on placebo. The investigators speculate that calcium pills disrupted normal adaptation to pregnancy and nursing.
[American Journal of Clinical Nutrition, Aug, 2010]