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Dietary calcium and magnesium, major food sources, and risk of type 2 diabetes in U.S. black women. van Dam RM, Hu FB, Rosenberg L, Krishnan S, Palmer JR. Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115, USA. rvandam@hsph.harvard.edu

OBJECTIVE: Inverse associations between magnesium and calcium intakes and risk of type 2 diabetes have been reported for studies in predominantly white populations. We examined magnesium, calcium, and major food sources in relation to type 2 diabetes in African-American women.

RESEARCH DESIGN AND METHODS: This is a prospective cohort study including 41,186 participants of the Black Women's Health Study without a history of diabetes who completed validated food frequency questionnaires at baseline. During 8 years of follow-up (1995-2003), we documented 1,964 newly diagnosed cases of type 2 diabetes.

RESULTS: The multivariate-adjusted hazard ratio of type 2 diabetes for the highest compared with the lowest quintile of intake was 0.69 (95% CI 0.59-0.81; P trend <0.0001) for dietary magnesium and 0.86 (0.74-1.00; P trend = 0.01) for dietary calcium. After mutual adjustment, the association for calcium disappeared (hazard ratio 1.04 [95% CI 0.88-1.24]; P trend = 0.88), whereas the association for magnesium remained. Daily consumption of low-fat dairy (0.87 [0.76-1.00]; P trend = 0.04) and whole grains (0.69 [0.60-0.79]; P trend <0.0001) were associated with a lower risk of type 2 diabetes compared with a consumption less than once a week. After mutual adjustment, the hazard ratio was 0.81 (0.68-0.97; P trend = 0.02) for magnesium and 0.73 (0.63-0.85; P trend <0.0001) for whole grains.

CONCLUSIONS: These findings indicate that a diet high in magnesium-rich foods, particularly whole grains, is associated with a substantially lower risk of type 2 diabetes in U.S. black women.

PMID: 17003299