Linear insulin-to-carbohydrate ratio may not fit all meal requirements
medwireNews: Using a linear insulin to carbohydrate ratio (ICR) to determine breakfast insulin requirements leads to significant differences in time in glycemic range (TIR) and hypoglycemia rates when meal carbohydrate quantities vary, shows a study in children and young adults.
Bruce King (John Hunter Children’s Hospital, Newcastle, New South Wales, Australia) and co-investigators say their results therefore “suggest that there is a non-linear relationship between breakfast [carbohydrate] content and insulin requirement to achieve postprandial glycaemic targets, consistent with other research.”
King and team found that when 31 individuals (mean age 16 years, 52% female) with type 1 diabetes were given a breakfast with 20 g of carbohydrate 15 minutes after an insulin bolus based on individualized ICRs, their proportion of TIR (3.9–10.0 mmol/L; 70–180 mg/dL) was 74% during the 5-hour postprandial period.
This was significantly higher than the 57%, 56%, and 63% of TIR recorded after breakfasts containing 50 g, 100 g, and 150 g of carbohydrate, respectively, and thus contradicted the researchers’ hypothesis that using a linear ICR would result in similar TIR.
Furthermore, hypoglycemia (blood glucose <4 mmol/L, or sensor glucose <3 mmol/L for ≥15 min) rates were significantly lower following the 20 g and 150 g breakfasts, at 20% and 26%, respectively, than after the 50 g and 100 g breakfasts, at a respective 42% and 50%.
This resulted in odds for hypoglycemia that were a significant three to four times higher after the 50 g and 100 g meals than after the smaller and larger ones.
Taken together, these findings suggest that “[t]he required insulin dose relative to the meal [carbohydrate] quantity was higher for the 20 and 150 g [carbohydrate] meals compared to the 50 and 100 g [carbohydrate] meals,” King and co-authors write in Diabetic Medicine.
The researchers also observed differences in prostprandial glucose excursion patterns according to carbohydrate content. The 50 g and 100 g meals resulted in the highest initial mean excursions, while the 150 g meal had the lowest initial excursion, all before 100 minutes.
The 150 g meal also elicited a second, higher peak, at around 200 minutes that was sustained for the remainder of the postprandial period. King and team suggest this may be a result of delayed gastric emptying with the 150 g carbohydrate breakfast.
The authors believe their findings show that “[w]hen a linear ICR is optimized for a specific [carbohydrate] quantity, then it is only effective for a limited [carbohydrate] range around that quantity.”
Therefore: “Meals containing >100 g [carbohydrate] may require an increased meal insulin dose and extension of insulin action via a dual wave bolus or split bolusing to maintain normoglycaemia,” they add.
King et al also note that the breakfasts they used each contained the same ratios of carbohydrate, fat and protein meaning their findings “may not translate to meals with other macronutrient compositions.”
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