WHI Study Shows Unexpected Outcomes for Calcium and Vitamin D

WASHINGTON, D.C., February 15, 2006 – 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. The studies, one assessing calcium and vitamin D supplementation on the risk of fractures, and the other on these nutrients’ effects on the risk of colorectal cancer, are part of the Women’s Health Initiative (WHI), sponsored by the National Institutes of Health (NIH) and the National Heart, Lung and Blood Institute (NHLBI).

“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, Ph.D., vice president, scientific and international affairs, Council for Responsible Nutrition (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 of the studies that may account for the unexpected results.”

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 to 20 years for colorectal cancer could have played a role in the null results, given that the study duration averaged only seven years. The authors note that they will assess the longer-term effect of calcium and vitamin D supplementation in an ongoing follow-up.

Dr. Hathcock also pointed to some promising news from the fracture risk study, stating that “the study showed that calcium with vitamin D supplementation resulted in a modest but significant improvement in hip bone density in postmenopausal women and it’s very possible that if the study continued for a longer duration there would have been a significant reduction in fracture risk.” Noting the consistency of that point with other research, Dr. Hathcock continued, “Giving women an edge by building bone density earlier on helps bolster bones against the possible onset of osteoporosis later. Calcium and vitamin D supplementation can effectively increase bone density to help preserve women’s bone health for the long term.”

CRN is encouraged to hear that NIH will continue to look at the effects of supplementation over an extended period of time, given that vitamins and minerals are most appropriately taken consistently over the long term in conjunction with other healthy lifestyle choices.

The Council for Responsible Nutrition (CRN), founded in 1973, is a Washington, D.C.-based trade association representing dietary supplement industry ingredient suppliers and manufacturers. CRN members adhere to a strong code of ethics, comply with dosage limits and manufacture dietary supplements to high quality standards under good manufacturing practices.

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