WHI data support existing RDA for calcium, vitamin D: results fall short of hip fracture benefit.(Gynecology)

BETHESDA, MD. -- The current recommended dietary allowance for calcium of 1,200 mg/day for people older than 50 was supported by the results of the calcium and vitamin D trial that was part of the Women's Health Initiative.

Although the trial's results failed to prove the study's primary hypothesis that a daily supplement of calcium and vitamin D would significantly cut the incidence of hip fractures in postmenopausal women aged 50-79, the trial produced enough positive results to support the existing recommended dietary allowance, Dr. Rebecca D. Jackson said at a conference on the Women's Health Initiative, sponsored by the Department of Health and Human Services.

The study has so far not produced any evidence that a calcium and vitamin D supplement has any effect on the incidence of invasive colorectal cancer, which was a secondary outcome.

A practical guide for physicians is that each glass of milk or dairy serving provides about 300 mg of calcium.

Therefore, if a postmenopausal woman eats three to four dairy servings a day, she is probably getting enough calcium. If not, a calcium supplement is a good idea, said Dr. Johnson, a professor of medicine at Ohio State University, Columbus, and a principal investigator of the WHI.

After the WHI's calcium and vitamin D study was designed, it was piggybacked onto the two other studies that had already begun, the hormone therapy and diet modification trials.

More than 36,000 women who were already enrolled in one or both of these ongoing WHI studies were randomized to get a daily supplement of 500 mg elemental calcium and 200 IU vitamin D or placebo, and the participants were followed for an average of 7 years.