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Calcium May Help Prevent Colorectal Cancer

Calcium, whether taken as a supplement or in your diet, can help prevent colon cancer.

In a study involving more than 45,000 American women followed for about 8.5 years, researchers show that calcium can cut women's risk of colorectal cancer. The best results came from combining a calcium-rich diet with supplements. The results appear in the January 2005 issue of Cancer, Epidemiology, Biomarkers & Prevention.

At the start of the study, the women who were free of colorectal cancer were about 62 years old. They filled out a 62-item food survey, describing their diets for the previous year. The women also reported calcium intake from multivitamins and cancer-specific supplements.

During the study, 482 women developed colon or rectal cancer. Colon cancer is the third most common cancer found in men and women in the U.S. Nearly 105,000 people will be diagnosed with colon cancer this year in America, predicts the American Cancer Society. Routine screening is the best way to find colorectal cancer early so treatment can result in cure of the disease.

Some studies have suggested that vitamins might lower the risk of getting colorectal cancer, while others suggest that getting calcium in your diet helps reduce your risk of the disease.
The researchers didn't only want to see if calcium affected colon cancer. They also were curious about whether the source of calcium made a difference. Were calcium-rich foods or supplements more helpful? To find out, the women were grouped by their calcium intake from food and supplements.

Calcium's Effects

Calcium intake slashed colorectal cancer risk, whether the women got their calcium from foods or pills.

Women who ate the most calcium-rich foods (greater than 830 mg/day) were 26% less likely to have colorectal cancer, compared to women whose diets contained the least amount of calcium (less than 412 mg calcium per day). The best results were seen in women who got the most calcium from food and also took the highest level of supplements (consuming more than 412 mg/day from diet plus 800 mg/day from supplements). Their colorectal cancer risk was 46% lower than those who skimped on calcium from either source (those receiving less than 412 mg/day from diet and less than 800 mg/day from supplements).

Women who ate a lot of calcium-rich foods but didn't get as much calcium from supplements had intermediate results. Their risk of colorectal cancer was reduced by only 18%.

Regardless of the source, calcium was the key. The researchers aren't sure how it lowered colorectal cancer risk, but they ruled out other influences. For instance, vitamin D -- which often accompanies dairy products -- didn't explain the results.

Some studies have shown that calcium also cuts men's colorectal cancer risk, says Dr. Flood in a news release. However, he also says other research suggests that fat in dairy products could increase prostate cancer risk.


Flood, A. Cancer Epidemiology, Biomarkers & Prevention, January 2005; vol 14: pp 126-132.

American Cancer Society: "Overview -- Colon and Rectal Cancer: How Many People Get Colorectal Cancer?" News release, University of Minnesota.

Key concepts: calcium, colorectal cancer