The relationship between meal carbohydrate quantity and the insulin to carbohydrate ratio required to maintain glycaemia is non-linear in young people with type 1 diabetes: A randomized crossover trial

OBJECTIVE: To determine if the relationship between meal carbohydrate quantity and the insulin to carbohydrate ratio (ICR) required to maintain glycaemia is linear in people with type 1 diabetes.

METHODS: We used an open labelled randomized four-arm cross-over study design. Participants (N=31) aged 12-27 years, HbA1c ≤ 64 mmol/mol (8.0%) received insulin doses based on the individual's ICR and the study breakfast carbohydrate quantity and then consumed four breakfasts containing 20, 50, 100 and 150 grams of carbohydrate over four consecutive days in randomized order. The breakfast fat and protein percentages were standardized. Postprandial glycaemia was assessed by 5hrs continuous glucose monitoring. The primary outcome was percent time in range (TIR) and secondary outcomes included hypoglycaemia, glucose excursion and incremental area under the curve. Statistical analysis included linear mixed modelling and Wilcoxon signed rank tests.

RESULTS: The 20g carbohydrate breakfast had the largest proportion of TIR (0.74 ± 0.29 p<0.04). Hypoglycaemia was more frequent in the 50g (n = 13, 42%) and 100g (n = 15, 50%) breakfasts compared to the 20g (n = 6, 20%) and 150g (n = 7, 26%) breakfasts (P < 0.029). The 150g breakfast glucose excursion pattern was different to the smaller breakfasts with the lowest glucose excursion 0-2hrs and the highest excursion from 3.5hrs to 5hrs.

CONCLUSIONS: A non-linear relationship between insulin requirement and breakfast carbohydrate content was observed, suggesting that strenghtened ICRs are needed for meals with ≤20g and ≥150g of carbohydrate. Meals with ≥150g of carbohydrate may benefit from dual wave bolusing.