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Influence of Dietary Protein on Postprandial Glycemic Control

Consider protein intake in addition to counting carbohydrates when calculating insulin doses.

Even though HbA1c might be at goal, the postprandial hyperglycemia might play an important role in the development of complications in type-1 diabetes. Despite accurate carbohydrate counting and insulin administration, postprandial glycemic excursions are a significant problem for patients with type 1 diabetes. Based on current recommendations, carbohydrates are the major nutrients influencing the rise in glycemic index. However, some studies have shown that protein and fat may also contribute to postprandial glucose excursions. Protein-rich meals may lead to late and sustained rise in postprandial glucose resulting in increased insulin requirement in type 1 diabetes patients. Although algorithms for insulin dosing with protein have been suggested, previous studies have shown an increase in hypoglycemia with their use.

A study conducted by Megan A. Paterson, of the Hunter Medical Research Institute and the School of Medicine and Public Health at the University of Newcastle, Australia, and colleagues, was to determine the postprandial glucose dose-response curves to varying amounts of protein, independent of carbohydrate and fat. This was a randomized cross-over multi-centered trial that was conducted in two centers in Newcastle, Australia. The inclusion criteria were ages 7-40 years, HbA1c < 8.5%, Type 1 diabetes for more than 12 months and using either insulin pump therapy or multiple daily insulin injections (>4 injections) for more than 6 months, and a healthy BMI (18.50- 24.99) for adults and ­< 91st percentile for children and adolescents. The exclusion criteria were medical comorbidities and complications of diabetes.

27 participants were recruited who consumed six 150 mL whey isolate protein drinks [0g (control), 12.5, 25, 50, 75, and 100g) and two 150 mL glucose drinks (10 and 20g) without insulin, 4 hours after evening meals, for 8 days. Participants were randomized using an eight by eight Latin square design. The meals were standardized for protein, fat, and carbohydrates. Additionally participants fasted for 5 hours after the evening meal, and their activity too was standardized. Glucose was monitored for 300 minutes daily to assess postprandial glycemia.

The data collected showed that the 25, 75, and 100 gram protein drinks resulted in significantly lowering mean glucose responses between 60-120 minutes [(95% CI -1.57 to -0.54), (95% CI -1.63 to -0.57), (95% CI -1.74 to -0.71), P < 0.001)] when compared to control. During the 180-240 minutes time interval, 75 and 100 gram protein drinks showed higher mean glucose excursions [(95% CI 0.01-1.41, P = 0.045) and (95% CI 0.40-1.73, P = 0.002)]. The glycemic impact during the 240-300 minutes time interval was sustained for the 75 and 100-gram protein drinks with significantly higher excursions than control [(95% CI 0.93–2.36) and (95% CI 1.04–2.41) (both P < 0.001)]. In comparison to the 20 g glucose drink, the 75 and 100-gram protein drinks resulted in an ongoing rise in glucose levels post the 300 minutes study period.

Time to peak glucose levels was 60 minutes with 20 grams of glucose, and 90 minutes with 75 and 100 grams of protein. However, the 75 and 100 grams of protein’s glycemic excursions were the same as that of the 20 grams of glucose in 180 minutes. The glycemic excursions continued post the 300-minute study period in 75 and 100-gram protein drinks, however the 100 gram drink was statistically significantly longer when compared to the control (P = 0.021). The 12.5, 25, 50 or 75 gram protein or the 10 and 20 gram glucose group’s time to peak glucose levels over 300 minutes were not significantly different (all P >0.05).

This study demonstrated that > 75 grams of protein consumed could lead to a significantly higher postprandial glucose excursions between 3 to 5 hours, when compared to just drinking water (control). It also demonstrated that 75 and 100 grams of protein might produce late glycemic response similar to that from 10 and 20 grams of glucose. However, the glycemic response from proteins are delayed and sustained. The findings support recommendations for insulin dosing for meals high in protein content.

Practice Pearls:

  • Postprandial glucose dose-response curves were determined using varying amounts of protein and compared to the control (water).
  • 75 and 100 grams of protein resulted in delayed and sustained glycemic excursions compared to the control.
  • When calculating insulin doses, the amount of protein must be considered in meals containing high protein content.

Paterson MA, Smart CEM, Lopez PE, et al. Influence of dietary protein on postprandial blood glucose levels in individuals with Type 1 diabetes mellitus using intensive insulin therapy. Diabetic Medicine. 2015;1-7. Published Jan. 6, 2016

Researched and prepared by Sabair Pradhan, Doctor of Pharmacy Candidate USF College of Pharmacy, reviewed by Dave Joffe, BSPharm, CDE