The word diabetes is associated with sugar and carbs. To diagnose, treat and manage diabetes we focus on sugars, carbs and glucose levels. However, in regards to food, protein is the neglected child who serves equal attention (Bell et al., 2015). Protein can affect your blood glucose just as much. It only does it very differently than carbohydrates do.

In this post we will take a look at the impact of protein on your glucose values. We'll see this nutrient can both raise and lower glucose spikes, depending on different factors such as time of the day, type and amount. If you only want to have some practical examples of how to deal with protein you can scroll to the bottom.

Gluconeogenesis: Protein's Path to Glucose

While carbohydrates can cause your glucose levels to spike quickly, protein breakdown operates differently. Your body breaks it down into amino acids, which can be used to repair and build tissues and support body functions. However, here is the catch: if you eat more protein can also be converted to glucose through the process called "gluconeogenesis" (Nuttall & Gannon, 2004).

The word "gluconeogenesis", means "creating new glucose" (Nuttall & Gannon, 2004). This process primarily occurs in the liver, where amino acids are transformed into glucose molecules that enter your bloodstream. This glucose does not show up immediately. It builds slowly and usually takes hours, sometimes causing blood glucose levels to rise at unexpected moments hours later.

Interestingly, for people with type 2 diabetes, this process becomes even more significant. Normally, insulin helps in regulating glucose levels by signaling the liver to slow down or stop glucose production from protein (Rizza, 2019). However, due to insulin resistance in type 2 Diabetes, the liver does not properly respond to insulin. As a result, it keeps producing glucose through gluconeogenesis and this can lead to hyperglycemia (Roden, 2018).

The role of quantity

The recommended dietary allowance (RDA) suggests about 0.8 grams per kilogram of body weight (Levine et al., 2014). That usually means around 50--60 grams daily for the average adult.

There are different reasons to push well past this RDA:

• Fitness enthusiasts, athletes and bodybuilders looking to maximize muscle growth
• Keto or low-carb dieters replacing carbs with protein
• People with diabetes that are trying to stabilize their glucose levels

Type 1

In healthy people this will not lead so easily to hyperglycemia after eating (>10 mmol/L 2 hours after eating) or during fasting. But what if you have diabetes? A recent study in Australia by Paterson et al. shows that "75 grams or more of protein alone significantly increases postprandial glycaemia" in people with type 1 diabetes mellitus using insulin therapy. The effect is however very different over time. In the first 6--120 minutes there are lower glucose levels after eating protein than when eating glucose. However later on glucose levels rise about 1 to 4 mmol/L depending of the amount of protein. Keep this in mind as we will later get back to how to configure your loop for these situations.

Figure 1: Different amounts of protein taken in a protein shake 4 h after the evening meal in a group of 27 participants with type 1 diabetes (CHO = carbohydrates).

Source. Vigouiliook 2015 Effect of Replacing Animal Protein with Plant Protein on Glycemic Control in Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Type 2

In the case of type 2 diabetes, increasing the protein content in diet at the expense of carbohydrate can decrease the glucose levels over longer periods of time (at least 5-week period). The decrease has been shown to be similar to that of medication. Keep in mind that "eating more protein" doesnt count. It's reducing the calories from carbs and compensating it with protein that helps over longer periods of time to decrease glucose excustions and Hba1c.

Figure 2: The decrease in HbA1c in study of 12 participants with type 2 diabetes.

Source Nutell et al. 2004. Metabolic response of people with type 2 diabetes to a high protein diet.

The role of quality

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How your blood glucose responds to the kind or type of food you are eating, and not just protein. It is not only about quantity but also the quality of the food you consume. Let's say you are getting protein from soy, eggs, yoghurt and lentils. That is very different from getting it through red meat, protein shakes, bars, and powders.

Let's take a look at the source of the protein. Studies have shown that different protein sources affect blood glucose in markedly different ways (Chen et al., 2023). A study by Tian et al in2017 for instance showed that "animal protein could increase the risk of T2DM in both males and females, and plant protein decreases the risk of T2DM in females". A study from the Utrecht similaryly showed that "Diets high in animal protein are associated with an increased diabetes risk." (Sluijs 2009). In table 1 you can see a summary of the Tian et al study results.

Table 1: The increased risk of type 2 diabetes in regards to protein and protein source. Numbers are based on evaluation of 483,174 participants from eleven studies.

Source: Tian et al. Dietary Protein Consumption and the Risk of Type 2 Diabetes: A Systematic Review and Meta-Analysis of Cohort Studies 2017

Next to the source of food, there is also a big difference between processed and unprocessed foods.

Whole Foods offers:

• Balanced nutrition mainly includes fiber, vitamins, and minerals
• Natural satiety
• Slower digestion, minimizing glucose spikes (Chen et al., 2023)

On the other hand, ultra-processed protein sources may contain:

• Added sugars, sweeteners, and preservatives
• Low fiber content
• Ingredients that affect absorption

We could not find any studies correlating eating specifically proteins derived from whole foods with diabetes but there are large epidemiological studies that show an association between processed foods and diabetes in general. Below you can see a graph from study from Shutong et al. from the John Hopkins university from 2024. The study included 13,172 participants over a median follow up time of 21 years and found that "each additional serving of ultra-processed food consumed daily was associated with a 2% higher risk of diabetes". So, again, it is not just the quantity --- but also the quality. If you are on a high-protein diet, eat more whole foods and not the processed forms.

The Role of Timing

Morning Protein: Setting the Stage for Metabolic Success

Research suggests that protein consumption early in the day may help stabilize blood glucose levels throughout the day. A high-protein breakfast (30-40g) has been shown to reduce postprandial glucose excursions at subsequent meals. This is because protein decreases the glycemic index of a meal but also has an effect on the meals eaten after that (Moghaddam 2006) ---a phenomenon also known as the "second-meal effect" (Norton et al., 2022). Starting your day with a protein rich meal can thus positively influence your glucose response in subsequent meals.

Figure 3: A graph of a research study that found that eating a high-protein breakfast, especially when paired with lunch, can help keep the glucose levels more stable, not just breakfast but also after lunch and dinner .

Source: Xiao et al. 2022: Effect of a High Protein Diet at Breakfast on Postprandial Glucose Level at Dinner Time in Healthy Adults.

Pre-Exercise Protein: Potential Glucose Level Stabilizer

Research published found that when participants consumed more than 10 grams of protein before moderate-intensity exercise, experienced less time below range (Muntis 2024). "Pre‐exercise protein intakes of 10‐19.9 g and >20 g were associated with an absolute reduction of -4.41% ( p = .04) and -4.83% ( p = .02) time below range during physical activity compared with those who did not consume protein before".

Adding a small protein-rich snack before a workout might be a simple way to reduce the risk of exercise-related hypoglycemia and keep energy levels more consistent. However, it is important to note that some protein-rich foods can cause gastrointestinal discomfort. High-protein meals may slow gastric emptying, which can lead to bloating, cramping, or nausea during exercise, particularly in endurance sports (Jeukendrup, 2017; Rehrer et al., 1992). To avoid this, it is best to opt for easily digestible protein sources like yogurt, protein smoothie, or a small serving of eggs and allow at least 1-2 hours for your food to digest before working out (Burke et al., 2011).

Bedtime Protein: Double-Edged Sword

Consuming protein before bed can be a balancing act. Consuming 20-30 grams of protein in the evening has been shown to help prevent overnight hypoglycemia (Bell et al., 2015). However, if you consume more than 50 grams of protein, it may lead to increasing glucose levels at night. A pattern known as the dawn phenomenon (Rizza, 2019). This happens because of the protein's delayed effect on glucose levels through gluconeogenesis, which can quietly raise glucose levels while you sleep.

Figure x: The "Dawn" period after mid night, a slow and steady rise in glucose levels while no food is being eaten. There can be an sharper or earlier peak in the night when eating protein before bed time due to glucoeneogenesis.Source Nauk et al. 2019 Twenty-Four Hour Fasting (Basal Rate) Tests to Achieve Custom-Tailored, Hour-by-Hour Basal Insulin Infusion Rates in Patients With Type 1 Diabetes Using Insulin Pumps (CSII)

Individual Variability: Your Response May Be Unique

Perhaps the most important thing to know is the relevance of proteins and your blood glucose falls to the individual. However, some Factors influencing this variability include:

• Insulin sensitivity
• Diabetes type and duration
• Gut microbiome composition
• Concurrent medications

Recommendations

1. Monitor and Learn Your Response

Use your glucose monitoring tools to identify your personal protein response. Try conducting simple self-experiments:

• Consume a carb-free, high-protein meal (e.g., eggs and cheese)
• Monitor glucose for 5+ hours afterward
• Document your unique response pattern

2. Take protein into account

Type 1

General rules:

• Eat a high protein breakfast. This will help stabilize your glucose levels throughout the day.
• If you eat a lot of protein, make sure to add carbs to the calculation to cover gluconeogenesis.

The book "Think like a pancreas" from Gary Scheiner provides some concrete advice. When using protein in the carb calculations in the bolus wizard of your loop you can do the following:

• With low carb meals, add 50% of the protein content of the meal as carbs.
• With large portions of protein add 20gr carbs to the calculations.

For example If we eat a sandwich of 18 grams of carbs. With that we eat 3 eggs. This is about 18 grams of protein in total. So this will be in total 27 grams of carbs (18 for the bread and 9 for the eggs).

Type 2

General rules:

• Eat a high protein breakfast. This will help stabilize your glucose levels throughout the day.
• When you focus on high protein diet, make sure to eat a lot of whole foods and not processed foods.
• If you are on a high protein diet, make sure to compensate by reducing the amount of carbs you eat.

References

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Bell, K. J., Smart, C. E., Steil, G. M., & Brand-Miller, J. C. (2015). Protein counting: An idea whose time has come? Pediatric Diabetes, 16(7), 485--492. https://doi.org/10.1111/pedi.12265

Burke, L. M., Hawley, J. A., Wong, S. H. S., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(sup1), S17--S27. https://doi.org/10.1080/02640414.2011.585473

Chen, Y., Li, L., Sun, Q., & Hu, F. B. (2023). Different sources of dietary protein and risk of type 2 diabetes: The importance of food sources of protein. American Journal of Clinical Nutrition, 118(2), 380--389.

Moghaddam, E., Vogt, J. A., & Wolever, T. M. (2006). The effects of fat and protein on glycemic responses in nondiabetic humans vary with waist circumference, fasting plasma insulin, and dietary fiber intake. The Journal of nutrition, 136(10), 2506-2511.

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