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Researchers studied more than 60,000 men and more than 60,000 women already participating in an American Cancer Society study of nutrition and cancer prevention. The participants were between 50 and 74 years of age when they enrolled in the study in 1992 and 1993. These findings were published in Cancer Causes and Control in 2003.
By 1997, 421 men and 262 women in the group had developed colorectal cancer. Researchers found that people who received calcium primarily from food did not have a lower risk of developing colon cancer than people who did not take supplements.
Total calcium intake (from diet and supplements) was associated with marginally lower colorectal cancer risk in men and women (RR = 0.87, 95% CI 0.67-1.12, highest vs lowest quintiles, p trend = 0.02). The association was strongest for calcium from supplements (RR = 0.69, 95% CI 0.49-0.96 for > or = 500 mg/day vs none). Total vitamin D intake (from diet and multivitamins) was also inversely associated with risk of colorectal cancer, particularly among men (RR = 0.71, 95% CI 0.51-0.98, p trend = 0.02). Dairy product intake was not related to overall risk.
Risk started to decrease with as little as 700 mg of total calcium a day and taking more than 1,200 mg a day did not seem to give any greater protection. The greatest reduction in risk was seen in people whose calcium came primarily from supplements rather than from diet.
McCullough ML, Robertson AS, Rodriguez C, Jacobs EJ, Chao A, Carolyn J, Calle EE, Willett WC, Thun MJ. Calcium, vitamin D, dairy products, and risk of colorectal cancer in the Cancer Prevention Study II Nutrition Cohort (United States). Cancer Causes and Control, 2003;14;1-12.
Epidemiology and Surveillance Research Department, American Cancer Society, 1599 Clifton Rd NE, Atlanta GA, 30309 USA.