Calcium Supplementation as Prophylaxis against Colon Cancer?

Dietary factors are major determinants of colorectal cancer risk. Especially a diet high in fat and low in fiber is recognized to be a risk factor. Dietary calcium has been suggested to be protective against colorectal cancer through the binding of intraluminal fatty acids and bile acids. Because of their cell-damaging properties these substances may stimulate colorectal epithelial cell proliferation and so promote colorectal cancer development. In this article data from in vitro, animal and human studies on the intraluminal effects of calcium, on its effects on colorectal epithelium and on the association between calcium intake and colorectal cancer are reviewed. It is concluded that at present it should be advised to bring dietary calcium intake into agreement with general dietary guidelines, but that high expectations of extra calcium as an effective mode of colon cancer prevention should not be encouraged.