A small trial suggests a low-fat vegan diet could help adults with type 1 diabetes reduce the amount of insulin they need without cutting calories or carbohydrates.
Researchers randomised 58 adults to either a low-fat vegan diet or a conventional portion-controlled plan for 12 weeks.
Those in the vegan group ate only plant foods and kept added fats low (roughly 75% of energy from carbohydrate, 15% from protein, and 10% from fat; no animal products).
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Both groups met weekly with dietitians.
By the end of the study, the vegan group cut their total daily insulin by an average of 12.1 units about a 28% reduction while the portion-controlled group saw no meaningful change.
Importantly, there was no increase in hypoglycaemia or hyperglycaemia, and HbA1c improved in both groups (−0.8 percentage points on the vegan diet vs −0.6 on the portion-controlled plan; between-group difference not significant).
Participants on the vegan diet also lost around 5.2 kg on average over 12 weeks.
Weight loss and lower fat intake likely improved insulin sensitivity, which may explain the lower insulin requirements.
Earlier analyses of the same trial reported improvements in blood lipids and kidney markers in the vegan group as well.
The researchers also modelled insulin spend using US pricing and found a 27% drop in daily insulin cost for the vegan group.
That cost figure won’t translate directly to the UK, but using less insulin and simplifying dosing could still matter for people and services. As ever, bigger and longer studies are needed.
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What this means in practice
This isn’t a cure for type 1, and nobody should change insulin doses or make major diet shifts without speaking to their diabetes team first.
But it does add to the evidence that, for some people with type 1, a carefully planned low-fat plant-based approach supported by a clinician and dietitian may improve insulin sensitivity and reduce day-to-day insulin needs while maintaining good glucose control.
If you’re considering it, remember vitamin B12 supplementation is essential on a vegan diet.
Sources: BMC Nutrition secondary analysis (2025) and the original 12-week randomised trial (2024).
