Vitamin C intake modify the impact of dietary nitrite on the incidence of type 2 diabetes: A 6-year follow-up in Tehran Lipid and Glucose Study

Abstract

© 2016 Background There is no epidemiological study on the association between dietary nitrate (NO 3 ) and nitrite (NO 2 ) and intakes and the risk of type 2 diabetes (T2D). Objective The aim of this study was therefore to examine the potential effect of dietary NO 3 and NO 2 on the occurrence of T2D. Design This longitudinal study was conducted within the framework of the Tehran Lipid and Glucose Study (TLGS) on 2139 T2D-free adults, aged 20–70 years, followed for a median of 5.8 y. Dietary intakes of NO 3 and NO 2 were estimated using a 168-food items validate semi-quantitative food frequency questionnaire, at baseline. Multivariate Hazard Ratios (HR) and 95% confidence intervals (CI), adjusted for diabetes risk score (DRS), and dietary intakes of fat, fiber and vitamin C, were calculated for residual energy-adjusted NO 3 and NO 2 intakes. Since significant interaction (P = 0.024) was found between NO 2 and vitamin C intakes in the multivariable model, stratified analyses were done for < and ≥ median vitamin C intakes. Results Median (inter quartile range; IQR) daily intake of NO 3 and NO 2 were 410 mg/d (343–499) and 8.77 mg/d (7.53–10.2). An increased r isk of T2D was observed among participants who had higher intake of total and animal-based NO 2 in participants who had low vitamin C intake (HR = 2.43, 95% CI = 1.45–4.05, HR = 1.88, 95% CI = 1.12–3.15, respectively). We found no significant association between NO 3 in overall, and plant- and animal sources as well, with the risk of T2D. Plant-derived NO 2 was also unrelated to incidence of T2D. Conclusion Our findings indicated that higher intakes of total and animal-based NO 2 may be an independent dietary risk factor for development of T2D in subjects with lower vitamin C intakes.