A 12-week randomized clinical trial published in BMC Nutrition found that a low-fat vegan diet significantly reduced daily insulin use and insulin costs in adults with type 1 diabetes, compared to a conventional portion-controlled diet.
The study was conducted by researchers from the Physicians Committee for Responsible Medicine, University of Michigan, University of Utah and George Washington University School of Medicine & Health Sciences.
The trial included 58 adults with type 1 diabetes. Participants were randomly assigned to either a low-fat vegan diet or a portion-controlled diet for 12 weeks. The vegan diet emphasized plant-based foods, with about 75% of calories from carbohydrates, 15% from protein and 10% from fat, while minimizing added fats. The portion-controlled group followed individualized meal plans that reduced calorie intake for overweight participants and emphasized consistent carbohydrate intake.
By the end of the study, those following the vegan diet reduced their total daily insulin dose by 28%, or 12.1 units per day. In contrast, the portion-controlled group saw no significant change. The between-group treatment effect was −10.7 units per day.
Insulin costs also declined sharply in the vegan group. Using Federal Supply Schedule pharmaceutical pricing and expressed in 2024 dollars, researchers found a 27% reduction in daily insulin costs, equating to $1.08 per day. The portion-controlled group experienced no meaningful change in insulin expenses.
Importantly, these reductions occurred without an increase in hypoglycemic or hyperglycemic events. Hemoglobin A1c levels fell in both groups, by 0.8 percentage points in the vegan group and 0.6 percentage points in the portion-controlled group, with no significant difference between the two.
Participants in the vegan group also lost an average of 5.2 kilograms, compared to no significant weight change in the portion-controlled group. Researchers suggest that reductions in liver and muscle fat may have improved insulin sensitivity, helping explain the lower insulin requirements.
The study concludes by stating “This study has demonstrated that a low-fat vegan diet, without limits on calories or carbohydrate intake, significantly reduced insulin use and insulin costs in people with type 1 diabetes. The study suggests the potential health and financial benefits of a low-fat vegan diet in type 1 diabetes management. Larger trials with longer follow-up are needed to confirm these findings.”
