Calcium, Phosphorus, Dairy May Ward Off Colon Cancer

NEW YORK (Reuters Health) - New research supports the hypothesis that calcium, dairy products and phosphorus exert a protective effect with regard to the progression of precancerous adenomas (polyps) to colorectal cancer.

"A protective effect of calcium and/or dairy products on colorectal cancer has been reported in epidemiological studies but the findings are considered inconsistent," Dr. François Clavel-Chapelon, of Institut Gustave Roussy, France, and colleagues point out in the International Journal of Cancer. "In particular, it is unclear whether they act at a particular step of the adenoma-carcinoma sequence."

The researchers prospectively examined the association between intakes of dietary calcium, phosphorus, vitamin D, and dairy products and the risk of precancerous adenomatous polyps and colorectal cancer in women enrolled in a French study.

Included in the study of risk factors for adenoma were 516 adenoma cases, including 175 high-risk adenomas, and 4804 polyp-free subjects. Included in the colorectal cancer study were 172 cases and 67,312 cancer-free subjects.

A self-administered questionnaire completed at baseline was used to assess diet. Patients were followed-up for a median 3.7 years in the adenoma study and 6.9 years in the cancer study.

Increasing intake of total dietary calcium was significantly associated with a decreased risk of adenoma. Increasing calcium intake was also associated with a trend toward a decreased risk of colorectal cancer.

Increasing consumption of phosphorus and dairy products also decreased the risk of adenoma

No protective effect against colorectal cancer was observed for any dairy product, except for high milk consumption, but this did not reach statistical significance.

No effect was observed for vitamin D but this may be explained by the low dietary intake of vitamin D in the population, as most dairy products available in France during the dietary assessment period were not vitamin-enriched.

"Our findings support the hypothesis that intakes of total dietary calcium and phosphorus reduce the risk of colorectal tumour at all stages of the adenoma-carcinoma sequence," the investigators conclude, "while dietary vitamin D does not appear to be associated with colorectal tumour risk."

SOURCE: International Journal of Cancer October 20, 2005.