Calcium: Good for More than Just Bones

Women may decrease their risk of developing colon and rectal cancer (colorectal cancer) by up to 45% by getting high amounts of calcium from diet and supplements, reports a study in Cancer Epidemiology, Biomarkers, and Prevention (2005;14:126–32).

Colorectal cancer is the second leading cause of cancer deaths in the United States. People with a close relative, such as a parent or sibling, with colorectal cancer and those with inflammatory conditions of the colon such as Crohn’s disease and ulcerative colitis are more likely to develop colorectal cancer. Smoking and physical inactivity are additional risk factors. Diets high in fat (particularly animal fat) and red and processed meats, and diets low in calcium, folic acid, fiber, and vitamins A, C, and E may increase the risk of colorectal cancer. Vegetables in the Brassica family such as broccoli, cabbage, and Brussels sprouts are thought to have a protective effect.

Several recent studies have shown calcium to decrease the risk of colorectal cancer. Although the mechanism is not fully understood, it may be related to calcium’s ability to bind bile acids the liver secretes into the intestinal tract. Although bile acids play an important role in normal digestion in the small intestine, their presence in the large intestine (colon) may contribute to colon cancer development. Once the bile acids are bound to calcium, however, they may be less harmful to the lining of the colon. Calcium may also act by directly inhibiting the growth of cancer cells.

The new study investigated the relationship between calcium intake and the risk of developing colorectal cancer in 45,354 women whose average age was 62. The women answered detailed questionnaires about the type and frequency of foods eaten and calcium intake from supplements. The participants were then followed for eight and a half years.

By the end of the study period, 482 women had developed colorectal cancer. The risk of developing cancer was 25% less among those women who consumed the greatest amount of calcium in their diets (average 985 mg per day) compared with the women who ate the least amount of calcium (average 337 mg per day). Women who took more than 800 mg per day of supplemental calcium also had a lower colorectal cancer risk than those women who took less calcium. Women with the highest total calcium intake from both diet and supplements had a 45% reduction in colorectal cancer risk compared with women with the lowest total calcium intake.

The results of this study suggest that both dietary and supplemental calcium decrease the risk of developing colorectal cancer. It appears that calcium from dietary sources may be most effective, as less dietary calcium provided the same risk reduction as higher amounts of supplemental calcium.

Kimberly Beauchamp, ND, received her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She is a co-founder and practicing physician at South County Naturopaths, Inc., in Wakefield, RI. Dr. Beauchamp teaches holistic medicine classes and provides consultations focusing on detoxification and whole-foods nutrition.

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