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

- We assessed effect of dietary nitrate/nitrite exposure and the occurrence of type 2 diabetes.
- Dietary nitrate was not related to risk of type 2 diabetes.
- Total and animal-based nitrite increased risk of type 2 diabetes in subjects with lower vitamin C intakes.

BackgroundThere is no epidemiological study on the association between dietary nitrate (NO3) and nitrite (NO2) and intakes and the risk of type 2 diabetes (T2D).ObjectiveThe aim of this study was therefore to examine the potential effect of dietary NO3 and NO2 on the occurrence of T2D.DesignThis 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 NO3 and NO2 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 NO3 and NO2 intakes. Since significant interaction (P = 0.024) was found between NO2 and vitamin C intakes in the multivariable model, stratified analyses were done for < and ≥ median vitamin C intakes.ResultsMedian (inter quartile range; IQR) daily intake of NO3 and NO2 were 410 mg/d (343-499) and 8.77 mg/d (7.53-10.2). An increased risk of T2D was observed among participants who had higher intake of total and animal-based NO2 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 NO3 in overall, and plant- and animal sources as well, with the risk of T2D. Plant-derived NO2 was also unrelated to incidence of T2D.ConclusionOur findings indicated that higher intakes of total and animal-based NO2 may be an independent dietary risk factor for development of T2D in subjects with lower vitamin C intakes.