Magnesium intake and colorectal tumor risk: a case-control study and meta-analysis

Background: Dietary magnesium might be related to colorectal tumor risk through the pivotal roles of magnesium in cellular metabolism, insulin resistance, and systemic inflammation. Objective: We evaluated the hypothesis of whether higher dietary magnesium intake is associated with reduced colorectal tumor risk. Design: A case-control study on colorectal adenomas (768 cases; 709 polyp-free control subjects) and a meta-analysis of colorectal adenomas (3 case-control studies) and carcinomas (6 prospective cohort studies) were conducted. Dietary magnesium was estimated from food-frequency questionnaires in the case-control study and most studies in the meta-analyses. Data analysis comprised multiple logistic regression analysis (case-control study) and fixed- and random-effects meta-analyses. Results: The case-control study showed a nonsignificant inverse association between dietary magnesium intake and risk of colorectal adenomas (OR for every 100-mg/d increase: 0.81; 95% Cl: 0.62, 1.06). However, inverse associations were observed only in subjects with BMI (in kg/m(2)) >= 25, in subjects aged >= 55 y, and for advanced adenomas. Associations did not vary by the calcium-to-magnesium intake ratio. In the meta-analysis, every 100-mg/d increase in magnesium intake was associated with 13% lower risk of colorectal adenomas (OR: 0.87; 95% Cl: 0.75, 1.00) and 12% lower risk of colorectal cancer (RR: 0.88; 95% CI: 0.81, 0.97). Conclusions: Our findings support the hypothesis that higher intakes of dietary magnesium are associated with lower risk of colorectal tumors. The consumption of magnesium-rich foods may be a new avenue to explore further in the search for cancer-prevention strategies. Am J Clin Nutr 2012;96:622-31.