Longitudinal associations of nutritional factors with glycated hemoglobin in youth with type 1 diabetes: the SEARCH Nutrition Ancillary Study

Background: Improved glycated hemoglobin (Hb A(1c)) delays the progression of microvascular and macrovascular complications in individuals with type 1 diabetes (T1D). We previously showed that higher baseline intakes of n-3 (omega-3) fatty acids and leucine are associated with preserved beta cell function 2 y later in youth with T1D. Objective: In the current study, we extend this work to explore the longitudinal associations of nutritional factors with Hb A(1c) in youth with T1D. Design: We included 908 T1D youth with baseline and follow-up Hb Ale measurements. Nutritional factors assessed at baseline were as follows: breastfeeding status and timing of complimentary food introduction; intakes of leucine, carbohydrates, protein, fat, and fiber estimated from a food-frequency questionnaire (FFQ); and plasma biomarkers for vitamins D and E, eicosapentaenoic acid (EPA), and docosahexaenoic acid. We fit linear regression models adjusted for baseline Hb Ale, sociodemographic variables, diabetes-related variables, time between baseline and follow-up visits, saturated fat, physical activity, and for NVQ-derived nutrients, total calories. The vitamin D model was further adjusted for season and body mass index z score. Results: The mean +/- SD age and diabetes duration at baseline was 10.8 +/- 3.9 y and 10.1 +/- 5.8 mo, respectively. A total of 9.3% of participants had poor Hb Ale (value >= 9.5%) at baseline, which increased to 18.3% during follow-up (P < 0.0001). Intakes of EPA (beta = -0.045, P = 0.046), leucine (beta = -0.031, P = 0.0004), and protein (beta = -0.003, P = 0.0002) were significantly negatively associated with follow-up Hb A(1c) after adjustment for confounders. Intake of carbohydrates was significantly positively (beta = 0.001, P = 0.003) associated with follow-up Hb A(1c) after adjustment for confounders. Conclusions: Several nutritional factors may be associated with Hb Ale during early stages of disease progression in youth recently diagnosed with T1D. In addition to the overall role of major macronutrients such as carbohydrates and protein, leucine and n-3 fatty acid intakes, such as of EPA, may be important for long-term glycemic control.