Colon cancer and dietary fat, phosphate, and calcium: a hypothesis.

Increased dietary fat was suggested to promote colon cancer by increasing the levels of free ionized fatty acids and bile acids in the colon contents. In the presence of calcium ions the irritating and toxic effects of the free acids on colon epithelial cells could be reduced by being converted to insoluble calcium soaps. The level of supplementary dietary calcium to supply adequate calcium and thus reduce the potential toxicity of dietary fat was considered.