How might calcium help prevent cancer?
Although the exact mechanism by which calcium may help reduce the risk of colorectal cancer is unclear, researchers know that, at the biochemical level, calcium binds to bile acids and fatty acids in the gastrointestinal tract to form insoluble complexes known as calcium soaps. This reduces the ability of the acids (or their metabolites) to damage cells in the lining of the colon and stimulate cell proliferation to repair the damage. Calcium may also act directly to reduce cell proliferation in the lining of the colon or cause proliferating colon cells to undergo differentiation, which, in turn, leads to a reduction in cell proliferation. Calcium also may improve signaling within cells and cause cancer cells to differentiate and/or die (25, 26).
How does the body absorb calcium from foods and supplements?
Calcium is absorbed passively (no cellular energy required) in the intestines by diffusing through the spaces between cells. It is also absorbed actively (cellular energy required) through intestinal cells by binding to a transport protein known as calbindin. The production of calbindin is dependent on vitamin D (27).
Does NCI recommend the use of calcium supplements to prevent colorectal cancer?
No. Although substantial evidence suggests that calcium may provide some protection against colorectal cancer, the evidence of potential benefit from calcium supplements is limited and inconsistent. Therefore, NCI does not recommend the use of calcium supplements to reduce the risk of colorectal or any other type of cancer. Note: The information in this fact sheet is not to be used as the basis for making health claims about calcium-containing products.
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Source: National Cancer Institute.