A growing body of studies is reporting protective effects of calcium-rich dairyfoods for colorectal cancer, a condition that accounts for nine per cent of all new cancer cases and kills half a million people every year worldwide.
"Our findings support the hypothesis of a protective role for calcium in colorectal cancer risk in both men and women, as a protective role for intakes of vitamin D, milk, and dairy products in men and in women who did not use supplemental calcium," wrote lead author Song-yi Park from the University of Hawaii.
Last year, researchers from Sweden reported that a diet rich in dairy products could cut the risk of colorectal cancer by half, but the authors did not attempt to measure the impact of vitamin D status, and called for future studies to look into the effects of this vitamin.
The new study, published in the current issue of the American Journal of Epidemiology addresses this need and not only supports the observation that calcium and dairy protect against colorectal cancer, but reports that vitamin D may have a protective effect, particularly in men.
The Multiethnic Cohort Study based in Hawaii and Los Angeles recruited 85,903 men and 105,108 women (average age 60, average BMI 26 kg per sq. m) and calculated nutritional intake from the diet and supplements using a food frequency questionnaire with over 180 food items.
During the follow-up period of 7.3 years 2,110 incident cases of colorectal cancer (1,138 in men and 972 in women) were documented by the researchers. After adjusting the results for potential confounding factors such as age, smoking habits, BMI, fibre intake, Park and co-workers divided calcium, vitamin D and calcium intake into five groups (quintiles).
The researchers report that the highest intake (at least 611 mg per 1,000 kcal per day) of total calcium intake (from foods and supplements) was associated with a 30 and 36 per cent reduction in colorectal cancer risk in men and women, respectively. Compared to the lowest intake (less than 288 mg per 1,000 kcal per day).