Calcium is not only vital for maintaining strong bones, it also appears to reduce the risk of colorectal cancer, too, according to a new U.S. study of nearly half a million older men and women.

In the study, researchers analyzed data from 492,810 adults aged between 50 and 71 - 293,907 men and 198,903 women - who participated in the National Institutes of Health-AARP Diet and Health Study. Participants reported how much and how often they consumed different foods, including dairy products rich in calcium. They also were asked whether or not they were taking dietary supplements. The medical records for cases of cancer were checked among all the volunteers.

After monitoring their progress for an average of seven years, the investigators found that total calcium intake was not associated with a lower risk of cancer in general in men, but women who were taking up to 1,300 mg of calcium each day had a lower risk of cancer overall. In particular, there were nearly 37,000 cancer cases developed in men and 16,600 in women.

The one fifth of men who took calcium mostly through food and supplements - approximately 1,530 milligrams per day - were 16 per cent less likely to develop cancers of the digestive system compared to those who took the least (526 mg). For women, those in the top fifth of calcium consumption (1,881 mg per day) had a 23 per cent lower risk compared to women in the lowest fifth of intake (494 milligrams).

Why calcium should influence cancer risk differently in women and in men is not clear, said Yikyung Park, Sc.D., a staff scientist at the National Cancer Institute, and a lead author of the study. "One can speculate that hormonal or metabolic factors contribute to this difference," she added.

According to Dr. Park, "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. Calcium has been shown to reduce abnormal growths and induce normal growth of cells in the gastrointestinal system and breast. Additionally, it binds to bile and fatty acids, potentially reducing damage to the mucous membrane in the large intestine.

The research was conducted because calcium has been hypothesized to play different roles in different types of cancer, but testing has not been complete yet, it is inconsistent and limited, Park said.

"In conclusion, 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," the authors wrote.

The U.S. Institute of Medicine recommends 1,200 milligrams of a daily calcium intake for all adults over the age of 50 and older. This is the exact amount which can be found in three cups of dairy products per day, that are considered as a main source of calcium. Other nondairy sources of calcium include beans, sardines, broccoli, spinach, and other green, leafy vegetables.

Tags: Colorectal - Colon Cancer, Nutrition, Vitamins

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