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What is the influence of dietary protein on post meal blood glucose?

Does protein effect blood sugar after a meal? Is there additional math we need to do for improved control after meals?

At present, those of us who use intensive insulin therapy understand how proper mealtime insulin dosing requires appropriate carbohydrate counting. This is based on the thought that carbohydrate is the main nutrient that influences our post meal blood sugar values. However, studies have demonstrated that protein and fat may also play a role in what happens to our post meal blood sugar.

The impact of dietary protein on blood sugar has long been a topic of debate. Early research hypothesized that 100 g of ingested protein produced 50–80 g glucose. Later research showed, it was only ~ 10 g of glucose that showed up in the circulation following consumption of 50 g of protein (this is a serving of cooked meat about the size of a full outstretched woman’s hand). This equates to ~ 1 g of glucose produced from every 5 g of protein consumed. The results of the study below are consistent with this and, indicate consumption of ~ 75g and 100 g of protein ALONE may produce late rises in blood glucose which is similar to that from 15 and 20 g of glucose. This is relevant, given that 20 g of consumed glucose causes significant post meal excursions when insulin is NOT given. However, because the impact from protein (usually not covered by insulin) is delayed and sustained it shows a good reason we need consider dosing for protein dependent on portion consumed.

Protein-rich meals may result in delaying the rise in blood glucose and produce a sustained high blood glucose.

This indicates a need for more insulin for such meals or snacks as well as a new way to think about dosing insulin to offset the slow and extended rise. There are some algorithms to calculate additional insulin for protein, but, when studied these seem to show an increase in post meal low blood glucose.

The effect of protein has been studied only as a component of mixed meals (with carbohydrate, fat and protein present). Until recently, there have been no published studies of the impact of ONLY protein in people with Type 1 diabetes. The objective of the study discussed below was to determine if there is an effect from protein alone. The study evaluated the post meal blood glucose dose-responsive curves to varying amounts of protein, independent of carbohydrate and fat.

(The study was conducted across two centers in Newcastle, Australia by M. A. Paterson1,2, C. E. M. Smart1,3, P. E. Lopez1,2, P. McElduff1, J. Attia1, C. Morbey 4 and B. R. King2,3)

The study  looked at participants with Type 1 diabetes mellitus who were 7–40 years old. The participants consumed six 150 ml whey isolate protein drinks

[0 g (control), 12.5g protein, 25g protein, 50g protein, 75g protein and 100g protein] as well as two 150 ml glucose drinks (10g carb and 20g carb) without insulin, in randomized order over 8 days, 4 h after the evening meal. Continuous glucose monitoring was used to assess post meal glucose excursions. The glucose beverage was used as a control to allow for evaluation of glucose excursion following consumption of carbs without bolus insulin for comparison to the data produced by a protein only “meal”, again without bolus insulin.

Results Data were collected from the 27 participants. The protein consumption of 12.5g and 50 g did not result in significant post meal glucose excursions compared with the control (water) through the 5hr study period (P > 0.05). However, when protein loads of 75g and 100g were consumed it showed lower glucose excursions than the control (water) in the 60–120 min post meal time, but HIGHER excursions in the 3hr to 5hr time period. In comparison with higher intake of 20g glucose, the larger protein loads resulted in a similar rise. There was a significant delay in the rise in blood glucose and sustained high blood glucose, starting at 3 hours post meal and continuing to 5 hours post meal. There was a statistically significant increase in the odds of glucose levels exceeding 180mg/dl (10 mmol/l) following 12.5, 50, 75, and 100g protein as well as the 20g of glucose in the 3hr to 5hr time frame. As expected, 20 g of glucose produced the earliest peak compared with other test drinks. A post meal blood sugar check rose within the first 30 min, peaked by 1hr and was sustained for 5hrs. By contrast, following consumption of 75g and 100 g protein, post meal blood glucose decreased from 0 to 90 min and did not begin to increase until between 90 and 100 min, when it became significantly higher than the control and reached the peak excursion observed from 20 g glucose close to 3hrs.


Conclusions Consuming 75g or more of protein without intake of carbs or fat is shown to significantly increase post meal glucose from 3 to 5 h in people with Type 1 diabetes mellitus using intensive insulin therapy. The effect on blood glucose resulting from high protein intake alone differs significantly from the increase from glucose in terms of time to highest blood glucose after the meal and length of time for the high blood sugar to extend post meal. This research supports recommendations for insulin dosing for large amounts of protein. (Australian New Zealand Clinical Trials Registry No.: ACTRN12513000215729)
The Bottom Line

Further research as well as dosing parameters would be most beneficial as we learn more and more about how food truly effects our control. This study truly supports the suggestion that insulin for protein-rich meals or protein only meals (think Fogo de Chão) could be dosed using an extended or dual-wave type bolus for those using insulin pump therapy. Lower post meal glucose excursions have previously been demonstrated using this bolus function. Further studies are needed to help define the amount of additional insulin required for protein-rich meals and importantly, how to effectively deliver these doses. There are so many different ideas about diet and so many ways people choose to eat (Paleo, Vegan, Raw, Low Carb High Fat, Mediterranean, etc.). It would be most beneficial for our educating bodies to come together and fine tune recommendations, based on research, to aid those of us with diabetes in appropriate dosing no matter what meal we choose to eat.


If you would like to learn more about managing blood sugar with high protein and/or high fat intake please call our office to set up a visit with Jennifer Smith RD, LD, CDE – Director of Lifestyle and Nutrition. 610-642-6055.

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