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Dietary magnesium lowers colorectal cancer risk

STOCKHOLM, SWEDEN. Colorectal cancer was diagnosed in an estimated 1 million people worldwide in 2002, accounting for more than 9 per cent of all new cancer cases. Researchers from the Karolinska Institutet have investigated whether magnesium intake affects colorectal cancer risk, through its role in cell activity and possible protective effect against oxidative stress. Previously, animal studies of magnesium supplementation have shown good results in reducing the incidence of colon cancer.

This prospective study was based on 61,433 women aged 40 to 75 years from the population-based Swedish Mammography Cohort. Women with previously diagnosed cancer were not included. During the follow-up of nearly 15 years there were 805 cases of colorectal cancer among the women – 547 colon cancer, 252 rectal cancer, and six of both types. Women with higher magnesium intakes tended to have lower intakes of energy and saturated fat and higher intakes of fiber and certain vitamins. Analysis showed that women with a magnesium intake at or above 255 mg/day had a 41 per cent lower risk of developing colorectal cancer than did women with an intake below 209 mg/day. Following adjustment for a variety of other dietary variables, the reduction in colorectal cancer risk remained similar at 39 per cent, and stood at 40 per cent once family history and several behavioural variables were taken into account. For each type of cancer individually, magnesium intake was inversely associated with both colon (34 per cent lower risk) and rectal cancer (55 per cent lower risk).

The researchers believed that a dose-response, linear association was occurring, and based on this assumption, they calculated that risk is reduced by 22 per cent for every 50 mg per day increase in magnesium (one banana or one serving of spinach or oatmeal). The authors conclude that the link needs confirmation through other large reliable studies, but these results add weight to the potential benefits of increasing consumption of foods with a substantial magnesium intake. They highlight the importance of fruits and vegetables, whole grain foods, and beans, and encourage well-designed studies of magnesium supplementation.
Larsson, S C, Bergkvist, L, Wolk, A. Magnesium Intake in Relation to Risk of Colorectal Cancer in Women. Journal of the American Medical Association, Vol. 293, January 2005, pp86-89

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