Total magnesium intake and colorectal cancer incidence in men

Background: Prior studies suggest dietary magnesium may be inversely associated with colorectal cancer incidence. Further, this association may be modified by calcium intake, vitamin D status and insulin resistance.

Methods: This study prospectively examines a cohort of men enrolled in the Health Professionals Follow-up Study (n = 51,529, aged 40-75 at baseline in 1986) without previous diagnosis of cancer at baseline. Total, dietary and supplemental magnesium intake were assessed using a validated Semiquanititative Food Frequency Questionnaire. Incident site-specific colorectal cancer cases were confirmed through medical records and pathology reports. Age- and multivariate-adjusted models were analyzed based on updated person-time using Cox proportional hazards modeling.

Results: After 18 years (768,370 person-years) of follow-up, 1013 incident colorectal cancer cases were documented. The mean quintiles of energy-adjusted total magnesium intake at baseline were 257, 306, 343, 384 and 479 mg/day. Magnesium intake was representative of U.S. adults, of which 80% do not meet the Recommended Dietary Allowance. The hazards ratio (HR) of colorectal cancer for the highest versus lowest quintile of cumulative updated total magnesium intake was 0.768 (95% CI: 0.632-0.932, p-trend = 0.0032). After full multivariate-adjustment this association was no longer statistically significant: HR = 1.048 (95% CI: 0.823-1.334).

Conclusions: This study reports no primary association between total, dietary or supplemental magnesium intake with colorectal cancer incidence. Further analyses will include effect modification by calcium intake, vitamin D intake and status, and BMI, and have implications for dietary or supplemental magnesium as a potential public health intervention for colorectal cancer prevention.