225955 Total magnesium intake and colorectal cancer incidence in men

Tuesday, November 9, 2010 : 9:35 AM - 9:50 AM

Melissa Y. Wei, MD, MPH , Department of Public Health and Preventive Medicine, Oregon Health & Science University School of Medicine, Portland, OR
Y. Liu , Dept of Epidemiology and Dept of Nutrition, Channing Laboratory, Harvard School of Public Health, Brigham and Women's Hospital & Harvard Med. School, Boston, MA
Edward L. Giovannucci, MD ScD MPH , Dept of Epidemiology and Dept of Nutrition, Channing Laboratory, Harvard School of Public Health, Brigham and Women's Hospital & Harvard Med. School, Boston, MA
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.

Learning Areas:
Chronic disease management and prevention
Clinical medicine applied in public health
Public health or related research

Learning Objectives:
1. Appreciate the biochemical and physiologic role of magnesium in the body and potential role in colorectal cancer prevention. 2. Analyze the role of magnesium with other key nutrients in colorectal cancer prevention, including calcium and vitamin D.

Keywords: Cancer Prevention, Nutrition

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: Fourth year medical student and MPH student in Epidemiology and Biostatistics. This study was conducted as part of my MPH thesis. Prior training: biology major with concentration in Nutrition at Cornell University. I have been conducting nutrition and chronic disease epidemiology research since 2002 and have published a few papers on colorectal cancer and adenoma.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.