Manganese intake from foods and beverages is associated with a reduced risk of type 2 diabetes

Background: Despite the hypoglycemic and antioxidant effects of manganese, only one recent Chinese study has investigated the association between dietary manganese intake and type 2 diabetes.

Methods: We recruited 19,862 Japanese men and women in the Japan Collaborative Cohort Study. The participants completed a food frequency questionnaire at the baseline survey (1988 = 1990) and a diabetes history at both baseline and 5-year surveys. We calculated the odds ratios (95 % CIs) of the 5-year cumulative incidence of self-reported physician-diagnosed type 2 diabetes according to quartiles of dietary manganese intake.

Results: Within the 5-year period, we confirmed 530 new cases of type 2 diabetes (263 in men and 267 in women) with a 5-year cumulative incidence of 2.7 % (3.6 % in men and 2.1 % in women). Higher manganese intake was inversely associated with the women's but not the men's cumulative risk of type 2 diabetes over the 5-year period. In a full model adjusted for the participants' characteristics, diabetes risk factors and a wide range of dietary variables, the multivariable odds ratios (95 %CIs) of type 2 diabetes across the increasing quartiles of manganese intake (Q1 to Q4) were 1.00, 0.97 (0.65, 1.43), 1.04 (0.67, 1.61) and 1.10 (0.64, 1.92), p-trend = 0.66 among men and 1.00, 0.74 (0.51, 1.06), 0.62 (0.41, 0.94) and 0.53 (0.31, 0.88), p-trend = 0.01 among women. The association was observed mainly for those with low iron intake in women, particularly premenopausal women.

Conclusion: Strong inverse associations between dietary manganese intake and risk of type 2 diabetes were observed in women but not men.