Magnesium intake and risk of colorectal cancer: a meta-analysis of prospective studies.

Epidemiologic studies have suggested that magnesium intake may be associated with a decreased risk of colorectal cancer (CRC), but the findings have been inconsistent. We aimed to assess this association by conducting a meta-analysis of prospective studies. We performed a literature search on PubMed database through July 2012 to identify prospective studies of magnesium intake in relation to CRC risk. Reference lists of the retrieved articles were also reviewed. A random-effects model was used to compute the summary risk estimates. Eight prospective studies containing 338,979 participants and 8000 CRC cases met the inclusion criteria. The summary relative risk (RR) for the highest vs lowest category of magnesium intake for CRC was 0.89 (95% CI, 0.79-1.00), with little evidence of heterogeneity. Restricting the analysis to six studies that have adjusted for calcium intake yielded a similar result. For colon and rectal cancer, the pooled RR was 0.81 (95% CI, 0.70-0.93) and 0.94 (95% CI, 0.72-1.24), respectively. In the dose-response analyses, the summary RRs for an increment of magnesium intake of 50 mg/day for colorectal, colon and rectal cancer were, respectively, 0.95 (95% CI, 0.89-1.00), 0.93 (95% CI, 0.88-0.99) and 0.93 (95% CI, 0.83-1.04), and there was some evidence of heterogeneity; omitting one study that substantially contributed to the heterogeneity yielded generally similar results, but with low heterogeneity. We detected no indication of publication bias. On the basis of the findings of this meta-analysis, a higher magnesium intake seems to be associated with a modest reduction in the risk of CRC, in particular, colon cancer.