<strong>Methyl donor nutrient intake and incidence of type 2 diabetes mellitus: results from 3 large US cohorts</strong>

Objective: We examined whether intake of methyl donor nutrients, including vitamins B2, B6, and B12, and folate, from foods and/or supplements is associated with type 2 diabetes risk.

Design and Methods: We included 203,644 women and men from the Nurses' Health Study (1984-2016), Nurses' Health Study 2 (1991-2017), and Health Professionals Follow-Up Study (1986-2016). Dietary data were collected every 2-4 years using semi-quantitative food frequency questionnaires. Cox proportional hazards models with time-varying covariates were used to evaluate associations between each nutrient and type 2 diabetes risk. Cohort-specific hazard ratios were combined using inverse variance-weighted fixed effects meta-analyses.

Results: During 4,900,181 person-years of follow-up, we documented 19,475 incident type 2 diabetes cases. In multivariable-adjusted meta-analyses, participants in the highest quintile of total vitamin B2 and B6 intakes had lower risk of diabetes compared with those in the lowest quintile [HR(95% CI): 0.93(0.89, 0.98) for B2; 0.93(0.89, 0.97) for B6]. When stratified by source, significant associations remained for B2 from food, but not from supplements. Neither association for B6 from food or supplements attained significance. No association was observed between total B12 intake and diabetes. However, B12 from food was marginally associated with a higher diabetes risk [HR(95% CI): 1.05(1.00-1.11)], but not after additional adjustment for red meat intake [HR(95% CI): 1.04(0.99-1.10)]. No evidence of association was observed between intakes of folate and diabetes.

Conclusions: Our study suggests that higher intake of vitamin B2 and B6, especially B2 from food sources, may be associated with a modestly lower type 2 diabetes risk.