Unexpected results from Ca/vit D study

Two major studies published in the February 16 issue of the New England Journal of Medicine on the role of calcium and vitamin D supplementation in the health of post-menopausal women showed disappointing outcomes inconsistent with the large body of scientific evidence and the prevailing wisdom about the beneficial effects of these two nutrients, says the US Council for Responsible Nutrition. The studies, one assessing calcium and vitamin D supplementation on the risk of fractures, and the other on these nutrients' effects on the likelihood of colorectal cancer, are part of the Women's Health Initiative, sponsored by the National Institutes of Health and the National Heart, Lung and Blood Institute .

"These are well-designed, solid studies, and we applaud the researchers, NIH and NHLBI for undertaking this important work of conducting large scale, randomized, double-blind, placebo-controlled trials such as WHI," said John Hathcock, vice president, scientific and international affairs, at the CRN. "As the findings from the various arms of the WHI are presented, we're seeing surprising results in a number of areas, including those from these two studies. Without discounting the value or importance of the studies, we think it is important for consumers not to over-interpret the results, as the authors themselves have noted limitations," he added.

The authors explain in the discussion of the hip fracture trial that the 400 IU of vitamin D per day used in the study may not have been enough to demonstrate the positive results on hip fracture risk previously shown to be effective. The majority of other studies reporting a benefit from calcium and vitamin D supplementation involved a vitamin D dose of 600 IU or higher. In addition, the study notes that subjects may have been too young to detect a beneficial effect on hip fracture. Authors of the study on colon cancer noted that the latency period of 10-20 years for colorectal cancer could have played a role in the null results given the study averaged seven years.