The International Agency for Research on
Cancer (IARC) released a report,
Vitamin D and
Cancer, on November 25, 2008. The report focused on the current state of knowledge and level of evidence of a causal association between
vitamin D status and
cancer risk. Although presenting and evaluating evidence for the beneficial role of UVB and
vitamin D in reducing the risk of
cancer, it discounted or omitted important evidence in support of the efficacy of
vitamin D. The report largely dismissed or ignored ecological studies on the grounds that confounding factors might have affected the findings. The report accepted a preventive role of
vitamin D in
colorectal cancer but not for
breast cancer.The only randomized controlled trial (RCT) on
cancer incidence that used a sufficiently high dose of
vitamin D (1,100 IU/day) and
calcium (1,400-1,500 mg/day) found a 77% reduction in the risk of all-
cancer incidence in postmenopausal women who received both, of which approximately 35% reduction in risk was attributed to
vitamin D alone. Unfairly, the report dismissed these findings on the basis of a flawed critique.The report called for RCTs of
vitamin D supplementation to settle the issue. Although RCTs theoretically would be beneficial, development of sound and effective public health policies does not necessarily depend on them, and the field of
vitamin D,
calcium and
chronic disease has reached the point where RCTs may not be ethical.The IARC report should therefore not form the basis for public health policy decisions.