Vitamin D and colorectal cancer:
Bischoff-Ferrari, HA et al made several strong points favoring a role of optimal levels of vitamin D in prevention of colorectal cancer. After reviewing studies, the authors stated that colon cancer incidence increases with further distances from the equator and a lower risk of colon cancer or colon adenomas occurs with higher 25-hydroxyvitamin D levels. Bischoff-Ferrari, HA et al stated that most vitamin D supplementation trials have resulted in inverse relationship of vitamin D supplements to colorectal cancer, and optimal 25-hydroxyvitamin D levels correlated with reduced colon mucosa proliferation. The author’s review of research also concluded that colon cancer cells also became less aggressive after exposed to vitamin D3 or 25-hydroxyvitamin D in vitro. The authors found the optimal level of vitamin D for all the health factors examined to start at 75 nmol/L (30 ng/mL), and the best was between 90 and 100 nmol/L (36-40 ng/mL). Based on this literature review, the authors suggest that the current intake of vitamin D for adults (200 to 600 IU) is insufficient to achieve optimal health outcomes. Among adults an intake of 1000 IU daily or greater is needed to achieve the optimal level of vitamin D. (23)