Monday , October 23 2017
Home / Resources / Articles / Carbohydrate Timing Affects Glucose and Insulin Excursions

Carbohydrate Timing Affects Glucose and Insulin Excursions

Meal sequencing may decrease glucose levels and insulin utilization.

Post-prandial glucose is an important determinant of glycemic control and a risk factor for diabetes-related complications. Previous studies have shown that ingesting the carbohydrates after a protein meal can stimulate insulin and delay gastric emptying leading to a lower glucose absorption. A previous study with 8 subjects with T2DM showed that whey protein consumed before a carbohydrate meal can stimulate insulin and incretin hormone secretion and slow gastric emptying, leading to marked reduction in postprandial glycemia.(1) There is, however, limited data supporting the right sequence of protein-carbs and its impact on insulin excursion and glucose levels within the 2 hours of approximate digestion time.

A study approved by the Weill Cornell Medical College Institutional Review included 16 patients with type 2 diabetes on a stable dose of metformin. They were given isocaloric meals on 3 separate days, 1 week apart after 12 hours of overnight fasting and were also instructed to maintain their usual diet during that time. The relevant nutrition facts of the meals include: 65 g of carbohydrates, 55 g of protein and 9.6 g of fat. They randomized them into 3 different meal plans: Carbohydrate First (CF) followed by proteins and vegetables meal after 10 minutes of rest, Carbohydrate Last (CL) preceded by the protein and vegetables sources after 10 minutes, and the last group was labeled Sandwich (S) since they ate all the meal components at the same time.

The participants’ blood levels were drawn every 30 mins for 3 hours: glucose and insulin excursion levels were reported. The average duration of diabetes among the participants was 3.8±2.4 years and the mean HbA1c was 6.5%±0.7%. Baseline fasting glucose levels for the three meal sequences showed no differences. Following the CL meal order, glucose levels plateaued between 90 mins and 3 hours postprandially; meanwhile, there were fluctuations in glucose concentrations in the CF meal condition, but the glucose level was significantly lower than CL at the 180-minute mark.

Postprandial mean glucose concentrations were significantly decreased by 20.8%, 30.2%, and 23.1% at 30, 60, and 90 min and the insulin excursions (iAUC0–180) was 53.4% lower (p<0.001) following the CL meal order when compared with CF. CL meal pattern showed declined postprandial glucose levels compared with the S meal pattern: a reduction of 19.8%, 25.2%, and 15.3% at 30, 60, and 90 min, respectively. The insulin excursion differences between CL and S were not statistically significant. The GLP-1 response to the CL meal order was greater compared with CF (p=0.019) and similar to the S meal condition. The glucagon excursions were not significantly different between the three meal conditions.

This study showed that meal sequencing can have a significant impact in the post-prandial glycemic control. These results showed that consuming proteins and vegetables prior to carbohydrates drops the pp-glucose levels and insulin excursion, meaning that lower insulin is needed for controlling the carbs intake. The addition of a third order of nutrients such as the sandwich has intermediate effects compared to CL and CF. A reasonable explanation for the attenuated glycemic response observed with the CL meal pattern is delayed gastric emptying and consequently slower rates of carbohydrate absorption, a mechanism that would not be entirely mediated by GLP-1.

Limitations of this study include small sample size and generalization of more complex meals, which can have different combinations of micronutrients. An important strength of this article includes a solid prospective trial that has real life application and benefit for diabetes management. Further studies on this principle should include data on gastric emptying and rates of nutrient absorption with extended follow-up beyond 180 min. (2)

Practical Pearls:

  • Timing of the carbohydrate sources can have significant effect on postprandial glucose levels and insulin excursion.
  • Consumption of carbohydrates after proteins and vegetables can delay gastric emptying thus reduce the former’s absorption.
  • Post-prandial glucose level is an important determinant of glycemic control and risk of diabetes related comorbidities.

References:

Ma J, Stevens JE, Cukier K, et al. Effects of a protein preload on gastric emptying, glycemia, and gut hormones after a carbohydrate meal in diet-controlled type 2 diabetes. Diabetes Care 2009;32:1600–2.

Alpana P Shukla, Jeselin Andono, Samir H Touhamy. Carbohydrate-last meal pattern lowers prostprandial glucose and insulin excursion in type 2 diabetes. BMJ Open Diabetes Research and Care. Volume 5, Issue 1, 2017

 

Fabio Rodriguez, PharmD. candidate 2018, LECOM School of Pharmacy