Association of diet with glycated hemoglobin during intensive treatment of type 1 diabetes in the diabetes control and complications trial

Background: Persons with type 1 diabetes have received widely varying dietary advice based on putative effects on glycemic control. Objective: The objective was to determine whether diet composition was associated with subsequent glycated hemoglobin (Hb A _1c) concentrations during intensive therapy for type 1 diabetes. Design: We examined associations between quantiles of dietary intake and Hb A _1c adjusted for age and sex in 532 intensively treated participants in the Diabetes Control and Complications Trial (DCCT) who had complete dietary data through 5 y of follow-up. Multivariate macronutrient density linear regression models tested the association of Hb A _1c at year 5 with macronutrient composition and were adjusted for age, sex, exercise, triglyceride concentration, body mass index (BMI), baseline Hb A _1c, and concurrent insulin dose. Results: Higher insulin dose, lower carbohydrate intake, and higher saturated, monounsaturated, and total fat intakes were associated with higher Hb A _1c concentrations at year 5. In age- and sex-adjusted multivariate macronutrient models, substitution of fat for carbohydrate was associated with higher Hb A _1c concentrations (P = 0.01); this relation remained significant after adjustment for exercise level, serum triglycerides, and BMI (P = 0.02) but was no longer significant (P = 0.1) after adjustment for baseline Hb A _1c and concurrent insulin dose. Conclusion: Among intensively treated patients with type 1 diabetes, diets higher in fat and saturated fat and lower in carbohydrate are associated with worse glycemic control, independent of exercise and BMI.