A study of 492,810 men and women has found a protective effect for calcium against digestive system cancers in both men and women.
In the February 23, 2009 issue of the American Medical Association journal Archives of Internal Medicine, Yikyung Park, Sc.D., of the National Cancer Institute and colleagues evaluated data from 293,907 men and 198,903 women who participated in the National Institutes of Health-AARP Diet and Health Study. The participants' intake of calcium from food and supplements was determined from responses to dietary questionnaires completed upon enrollment. Forty-nine percent of the men and 57 percent of the women used multivitamins that contain calcium, and 14 percent of the men and 41 percent of the women used individual calcium supplements.
Over the seven year average follow-up period, 36,965 cancers occurred among the male participants and 16,605 in the women. Although calcium intake was not associated with the combined risk of all cancers in men, for women, cancer risk declined with an intake of up to 1,296 milligrams per day, after which there appeared to be no further reduction. Women at this level of calcium intake experienced a 7 percent lower risk of all cancers compared with those whose intake was 494 milligrams or less. Cancers of the digestive system, including esophagus, stomach, pancreas, liver, and colorectal cancer, were reduced in both men and women whose calcium intake was high. For men whose total calcium intake was among the highest 20 percent at 1530 milligrams or more, there was a 21 percent lower risk of colorectal cancer compared with men whose intake was lowest at 526 milligrams, and for women whose intake was in the top one-fifth at 1881 milligrams per day, the risk was 28 percent lower. No signficant association with prostate or other nondigestive system cancers was observed.
"Dairy food, which is relatively high in potentially anticarcinogenic nutrients such as calcium, vitamin D and conjugated linoleic acid, has been postulated to protect against the development of colorectal and breast cancer," the authors explain. “The binding of calcium to bile and fatty acids in the gastrointestinal tract has been hypothesized to reduce damage to large-bowel mucosa.”
"Our findings suggest that calcium intake consistent with current recommendations is associated with a lower risk of total cancer in women and cancers of the digestive system, especially colorectal cancer, in both men and women," they conclude.