Context: Animal studies have suggested that dietary magnesium may play a role in the prevention of colorectal cancer, but data in humans are lacking.
Objective: To evaluate the hypothesis that a high magnesium intake reduces the risk of colorectal cancer in women.
Design, setting, and participants: The Swedish Mammography Cohort, a population-based prospective cohort of 61,433 women aged 40 to 75 years without previous diagnosis of cancer at baseline from 1987 to 1990.
Main outcome measure: Incident invasive colorectal cancer.
Results: During a mean of 14.8 years (911 042 person-years) of follow-up, 805 incident colorectal cancer cases were diagnosed. After adjustment for potential confounders, we observed an inverse association of magnesium intake with the risk of colorectal cancer (P for trend = .006). Compared with women in the lowest quintile of magnesium intake, the multivariate rate ratio (RR) was 0.59 (95% confidence interval [CI], 0.40-0.87) for those in the highest quintile. The inverse association was observed for both colon (RR, 0.66; 95% CI, 0.41-1.07) and rectal cancer (RR, 0.45; 95% CI, 0.22-0.89).
Conclusion: This population-based prospective study suggests that a high magnesium intake may reduce the occurrence of colorectal cancer in women.