Calcium has been hypothesized to reduce the risk of colon cancer, and in a randomized trial, calcium supplementation was associated with reduction in the risk of recurrent colorectal adenomas (Grau et al. 2003). High calcium intake or calcium supplementation may reduce the risk colorectal cancer.
Accumulating evidence shows that calcium supplementation regulates the growth pattern of colonic epithelium in the individual at high risk for colon cancer (Wargovich et al. 1992). An inverse association between dietary calcium intake and colorectal cancer risk was found in a study of 61,463 women (an average 11.3 years of follow-up). Women with the highest calcium intake (median 914 mg/day) had a reduced risk of colorectal cancer compared with women with the lowest intake (median 486 mg/day). Furthermore, the inverse association was found to be strongest in relation to distal cancers and among older women (Terry et al. 2002).
Calcium supplementation reduces colonic cell proliferation, in part, by decreasing the level of diacylglycerol (DAG). A high luminal level of DAG, a key factor in cell growth control, enhances colonic cell proliferation. Bacterial DAG production is increased by bile acids and phospholipids, both of which may be precipitated by calcium. Calcium was shown to alter fecal lipid composition and to reduce cell proliferation. Oral elemental calcium therapy, 2.4 or 3.6 g/day, for three months markedly reduced fecal DAG concentration and output without enhancing DAG production (Steinbach et al. 1994).
Twenty-two individuals with a history of resected adenocarcinoma of the colon, but free of cancer, were supplemented with 2000 or 3000 mg of calcium for 16 weeks. Calcium supplementation significantly decreased the primary bile acids concentration resulting in a healthier bile acid profile suggesting a protective effect of calcium on colon cancer (Lupton et al. 1996).
In high-risk individuals, the use of multivitamins has been shown to reduce the risk of adenoma formation (Whelan 1999). A reduced risk of colon cancer is associated with the use of vitamin C (Howe et al. 1992). Vitamins C, E, and A showed protection against the risk of developing colorectal cancer (Newberne et al. 1999). Low levels of selenium correlated with the presence of adenomas (benign tumors), whereas increased levels were associated with reduced risk of adenomas (Russo et al. 1997).