Postmenopausal women who took calcium and vitamin D supplements gained slightly less weight than those who did not and appeared better able to manage their weight over a seven-year period, Oakland researchers reported in a study published Monday.

"Postmenopausal women should be taking calcium anyway to prevent bone loss and weight gain prevention appears to be an added benefit," said Dr. Bette Caan, of Kaiser Permanente Division of Research in Oakland and lead author of the study.

The benefits were slight, but statistically significant, according to the study, published in the Archives of Internal Medicine. More than 36,000 women ages 50 to 79 were randomly assigned to receive either a daily dose of 1,000 milligrams of calcium plus 400 international units of vitamin D or a placebo. The women already were enrolled in the Women's Health Initiative clinical trial, a large, broad-based ongoing study of a variety of women's health concerns.

The women were weighed once a year over seven years.

After three years, the researchers noted that women who were taking the calcium supplement were better at preventing weight gain typically seen at middle-age than those taking a placebo.

"The group as a whole wasn't gaining weight but was maintaining their weight," Caan said.

At the end of the study, women who took the supplements weighed on average 0.28 pounds less than those who got the placebo.

"The benefits were greatest for those women who were not taking the recommended amount of calcium before the trial," Caan said.

Only about 40% of the women met the federal recommended daily intake of 1,200 milligrams of calcium before enrolling in the study.

Among the women not previously taking the recommended amount of calcium and assigned to receive the supplements, they weighed an average of 0.42 pounds less than those not receiving supplements by the end of the study.

After three years, the women previously not taking calcium had an 11 percent lower risk of gaining weight and a higher likelihood of maintaining a stable weight, within 2.2 pounds, than women taking a placebo.

The role of calcium in weight loss and maintenance remains controversial.

Some previous studies have suggested that calcium increases metabolism in fat cells and may decrease fatty acid absorption. And the dairy industry has touted calcium as an ally in the battle to lose weight and keep it off.

This study was funded by the National Institutes of Health.

Women should not see calcium pills as a weight-loss strategy, Caan cautioned, noting that the best way to maintain a healthy weight is to exercise regularly and eat a balanced diet.

From the May 23, 2007, Prepared Foods e-Flash