Vitamin D, Calcium, and Colorectal cancer.





Related Monographs

Consumer Data: Calcium Vitamin D
Professional Data: Calcium Vitamin D


Vitamin D is known as the "sunshine" vitamin because it is formed in the body by the action of the sun's ultraviolet rays on the skin. The fat-soluble vitamin is converted in the kidneys to the hormone calcitrol, which is actually the most active form of vitamin D. The effects of this hormone are targeted at the intestines and bones.

Vitamin D works synergistically with calcium in the body. Calcium is the most abundant mineral in the human body. Average healthy males have about two and a half to three pounds of calcium while females have about two pounds. Approximately 99 percent of calcium is present in the bones and teeth, which leaves only about one percent in cells and body fluids. While the most important function of calcium involves the maintenance of skeletal health, the small percentage of calcium outside the bones is used to maintain a variety of vital body functions.

A recent study published in the New England Journal of Medicine stated that previous studies have shown that a high intake vitamin D and calcium has been linked to a lower risk of colorectal cancer. However, randomized-trial data is lacking on supplementation and primary prevention. This study involved 36,282 postmenopausal women. Over 18,000 received 500mg of elemental calcium carbonate and 200 IU of vitamin D3 twice daily and 18,106 received a matching placebo for 7 years. After reviewing the data, invasive colorectal cancer incidence did not differ significantly between the two groups. The authors concluded that, “Daily supplementation of calcium with vitamin D for seven years had no effect on the incidence of colorectal cancer among postmenopausal women. The long latency associated with the development of colorectal cancer, along with the seven-year duration of the trial, may have contributed to this null finding.”1


1. Wactawski-Wende J, et al. Calcium plus Vitamin D Supplementation and the Risk of Colorectal Cancer. NEJM. Feb 2006. 354(7):684-96.