Background
Effective glucose management is essential to prevent complications in type 1 diabetes. While nutrition therapy is crucial, the optimal diet remains uncertain. Our systematic review and meta-analysis synthesized evidence from randomized controlled trials (RCTs) on the impact of various diets on glucose management in type 1 diabetes.
Methods
We systematically searched Medline, Embase, and Cochrane Library up to 11 November 2024 for RCTs on dietary patterns and glucose control outcomes in type 1 diabetes, including HbA1c, time in range (TIR), coefficient of variation (CV), hypoglycemia, insulin dose, and anthropometric characteristics. Two reviewers independently extracted data and assessed the risk of bias using the RoB-2 tool. We estimated summary mean differences (MD) with 95% CIs using random-effects models. The certainty of the evidence was evaluated using GRADE. The study protocol was registered in PROSPERO (CRD42023479252).
Findings
Out of 5287 studies, 35 RCTs involving children, adolescents, and adults with type 1 diabetes were eligible. Higher-fiber diets (≥35 g/day, 5 RCTs) reduced HbA1c (MD -0.46%, 95% CI -0.93 to 0.00, I(2) 65%) and hypoglycemia (MD -0.81 episodes/month, 95% CI -1.34 to -0.28, I(2) 0%), with moderate and low certainty of evidence, respectively. Carbohydrate-restricted diets (≤45% energy, 20 RCTs) improved TIR (MD 3.84%, 95% CI 2.24-5.44, I(2) 0%), CV (MD -3.24%, 95% CI -5.51 to -0.97, I(2) 53%), and insulin needs (MD -5.63 U/day, 95% CI -9.51 to -1.74, I(2) 70%), but not HbA1c, with low to moderate certainty of evidence. Higher-protein, low-glycemic index, gluten-free, Mediterranean, vegan, and intermittent fasting diets showed no effects on glucose management (1-6 RCTs), although certainty of evidence was low.
Interpretation
Maintaining a high-fiber diet while restricting other carbohydrates may improve glycemic control in individuals with type 1 diabetes. Further investigation is needed into long-term effects and other diets.
Funding
Swedish Research Council, Swedish Diabetes Foundation, and the Strategic Research Programme in Diabetes at Karolinska Institutet.