Commenting on the randomized, double blind, placebo-controlled trials, John Hathcock, PhD, vice president, scientific and international affairs, Council for Responsible Nutrition (CRN), Washington, D.C., said, 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 explained that in the hip fracture trial, 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 the subjects may have been too young to detect a beneficial effect on hip fracture.
Authors of the study on colon cancer also 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 will assess the longer-term effect of calcium and vitamin D supplementation in an ongoing follow-up.
Dr. Hathcock 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 its 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 womens bone health for the long term.