Discover How Low Protein Diets Transform Diabetes Management: The Ultimate Guide

Diabetes mellitus is a widespread metabolic disorder characterized by elevated blood glucose levels. The prevalence of diabetes has been steadily increasing, with an estimated 537 million adults aged 20-79 living with diabetes globally in 2021, and a further rise expected. Disruptions in insulin action and secretion contribute to the characteristic hyperglycaemia. Cells become resistant to insulin’s actions, most notably insulin-resistant glucose uptake in skeletal muscle which results in elevated blood glucose levels. Initially, the pancreas may produce extra insulin to compensate for insulin resistance. However, over time, the pancreatic beta cells may fail, leading to decreased insulin production and exacerbating high blood glucose levels. Diet, physical activity and body weight are key modifiable factors for the development of diabetes. Various diets aimed at weight reduction and improving insulin sensitivity are advocated for patients with diabetes, among them high-protein diets. Already a century ago dietary protein intake was investigating in relation glycemic control, due to its glucogenic properties as well as its stimulation of insulin and glucagon secretion. In addition, high-protein diets are recommended for weight-loss and maintenance, which might benefit diabetes risk reduction. However, the impact of high-protein diets or high protein consumption on insulin sensitivity and - risk of - diabetes is not straightforward. This article explores the complex relationship between low protein diets and diabetes, considering both the potential benefits and risks.

The Role of Protein in Diabetes Management

Protein is an essential nutrient that is found in every cell in our bodies and in our blood stream. Our bodies use protein for growth, maintenance, energy, and chemical reactions - our muscles are made of protein; protein builds and maintains our bones, hair, nails, and skin; protein helps to support our immune system; and protein is used to make hormones, like insulin and glucagon. Protein is made up of building blocks called amino acids. There are 20 different types of amino acids; nine are considered essential because the body can't make them on its own. Each amino acid has a different, but vital, role to play in the body. The protein you eat is classified as either complete or incomplete based on whether it contains all nine essential amino acids. Proteins from eggs, meat, fish, poultry, cheese, and milk are complete proteins. They contain all of the essential amino acids. Most plant proteins, such as nuts, seeds, beans, and grains, are incomplete. They do not have all the essential amino acids. Soy protein is the exception; it is a plant protein that provides all nine essential amino acids. You should eat a variety of proteins every day to make sure you get all of the amino acids your body needs, particularly if you are a vegetarian. Like carbohydrate, protein provides energy for the body; each gram of protein contains four calories. However, protein is not the body's preferred energy source. The body likes to use protein primarily to repair body tissue. Protein is a nutrient that has a minimal impact on blood sugar levels and has the added benefits of helping satisfy hunger.

Understanding Low Protein Diets

A low-protein diet requires you to restrict the amount of protein you consume, typically so that it constitutes 4-8% of your daily calories. This translates to somewhere between 20-50 grams of protein per day, depending on how many calories you consume. For comparison, the average person is generally recommended to get at least 10-15% of their daily calories from protein. This amount may increase for athletes, older adults and those with certain health problems.

Potential Benefits of Low Protein Diets in Specific Conditions

The benefits of a low-protein diet mostly apply to people with specific health conditions or diseases, rather than those who are generally healthy. Excess protein is typically broken down by the liver, producing a waste product called urea, which is excreted by the kidneys. Decreasing protein intake can ease the workload of the liver and kidneys, which can be beneficial for people with liver disease or impaired kidney function. This helps improve protein metabolism and prevents a buildup of urea in the bloodstream. Having high levels of urea in the blood causes symptoms like fatigue, loss of appetite, weight loss and changes in mental status. It may also be associated with a higher risk of type 2 diabetes and death in those with heart failure. Reducing protein intake is also necessary for those with genetic disorders that affect protein metabolism, such as homocystinuria and phenylketonuria. These disorders impair the breakdown of specific amino acids, so reducing protein intake can help minimize symptoms.

Observational Studies: Protein Intake and Diabetes Risk

Observational studies have identified a high protein intake as a risk factor for type 2 diabetes mellitus, and elevated circulating branched-chain amino acids (BCAA) levels are among the strongest predictors of future cardiometabolic risk. Besides calorie intake, fiber and carbohydrate consumption, also protein intake has been investigated in relation to diabetes risk in large scale observational studies. Within the setting of EPIC-InterAct, a large scale pan-European type 2 diabetes case-cohort, we were able to study the association between protein intake and risk of type 2 diabetes. After adjustment for important diabetes risk factors and dietary factors, the incidence of type 2 diabetes was higher in those with high intake of total protein and animal protein, not plant protein. Associations were stronger in women, more specifically obese women. A meta-analysis of several large population studies, including the large Nurses’ Health Studies and the Melbourne collaborative cohort study confirmed these observations: higher intakes of total and animal protein were both associated with increased risks of T2D, whereas higher plant protein intake tended to be associated with lower risk of T2D. High (animal) protein intake is in ‘free-living’ conditions in general related to a higher (saturated) fat intake, a lower fiber and vitamin intake, increased BMI and lower physical activity levels. These are known diabetes risk factors and could contribute to the positive association between protein intake and diabetes risk. In particular the BCAA attracted attention, as several studies identified high plasma levels of BCAA predicting diabetes risk, and decreased levels were associated with improvement in insulin resistance. BCAA, which include leucine, isoleucine and valine, are all essential amino acids with a relative high presence in various protein sources, in particular those from animal origin. BCAA have, next to protein synthesis, multiple important roles in human metabolism and several metabolic diseases. Although acute infusion of BCAA can introduce insulin resistance, plasma BCAA levels are not simply a consequence of a high (animal) protein intake. Elevated circulating BCAA levels can have multiple origins, including increased appearance in plasma due to food intake, protein breakdown and gut microbial synthesis, and/or alteration in disappearance due to protein synthesis, excretion and BCAA catabolism. With the latter, a dysfunctional-repressed-BCAA catabolism has been proposed as playing a large role. Thus the relationship between BCAA, insulin resistance and type 2 diabetes is much more complex, and characterised as a “two-way street”, with diabetes, obesity and insulin resistance contributing to elevated BCAA levels and vice versa. Several strategies are considered to lower BCAA levels and/or boost BCAA catabolism, which includes diet and exercise interventions, next to pharmaceutical approaches. Thus, observational data clearly identified a high (animal) protein intake under ‘free living’ non-restricted conditions to be associated with an increased risk of developing diabetes, with elevated circulating BCAA levels as biomarkers of disease risk.

Read also: Protein Coffee Smoothie Recipe

Protein Intake for Weight Loss and Maintenance

Protein intake is recommended to support weight-loss and weight maintenance, in particular to preserve lean mass when on calorie restriction. It is estimated that high protein intake (e.g., >1.0 g/kgBW/day) compared to normal protein intake (0.8 g/kgBW/day) can prevent a loss of 0.5-1.0 kg lean mass with moderate weight-loss. Adequate protein intake stimulates muscle protein synthesis and hence supports lean mass. In addition, dietary protein is more satiating than fat or carbohydrate, and dietary protein stimulates thermogenesis, both also facilitating weight loss and maintenance. As body weight, and body weight-loss, is a key factor in insulin resistance and glucose homeostasis, high-protein diets may improve cardiometabolic risk factors.

Impact of High Protein Diets on Cardiometabolic Risk Factors

A recent systematic review and meta- analysis of 54 randomised controlled trials in populations without diabetes confirmed the impact of high protein diets (i.e., 20-45 Energy%) versus low-protein diets (i.e., 10-23E%) on weight-loss and fat mass loss. But also systolic blood pressure, total cholesterol, triacylglycerol and fasting insulin levels, a marker of insulin resistance, were lower on HP diets. No significant differences were seen for glucose, HbA1c and insulin resistance as estimated by HOMA-IR, although fewer studies assessed these effects. In patients with diabetes, a high-protein, low carbohydrate weight-maintaining diet improved fasting plasma and 24-h glucose and HbA1c level. Although protein is known for its effect on insulin (and glucagon) secretion by the pancreas, the low glucose availability is probably the key in the impact of this diet. In a moderate weight-loss trial in obese women, a high-protein (1.2 g/kg/day) regular carbohydrate diet compared to a low protein (0.8 g/kg/day) diet reduced the WL-induced decline in lean tissue mass, but it also prevented the WL-induced improvements in muscle insulin signalling and insulin-stimulated glucose uptake.

The Role of Protein Source

Next, to total protein intake also protein source could play a role. In a randomised cross-over trial we compared two weight-maintenance high-protein diets (22En%) with different protein sources. Substituting 30 grams of protein daily from meat products with soy products in postmenopausal abdominally obese women led to improvements in various cardiometabolic risk factor, including insulin sensitivity as measured with an frequently sampled intravenous glucose tolerance test (FSIGT). Whether the protein itself explains these findings or the isoflavones associated with soy protein could not be concluded. From a systematic review on the effects of plant protein versus animal protein in healthy humans and those with a metabolic impairment, it was concluded that there is some evidence that the intake of plant protein, in particular soy protein associated with isoflavones, may prevent the onset of cardiometabolic risk factors like hypercholesterolemia and hypertension, but an effect on glucose homeostasis could not be concluded. From studies with individuals with diabetes, it was concluded that replacing sources of animal with plant protein leads to modest improvements in glycaemic control. Again, an important note is that changing plant-protein intake is in general part of changes in plant-based foods consumption with subsequent changes in other nutrients and dietary factors, like fiber, fat, micronutrients and energy. Altogether, in controlled intervention studies, high-protein (energy restricted) diets improve body weight and composition as well as multiple cardiometabolic risk factors including insulin resistance and glycaemic control. High plant protein intake, as part of a plant-based diet, may have stronger effects compared to animal protein, as part of an animal-based diet, but mainly on lipids, not on glucose homeostasis. With other dietary factors than plant protein, like fat, fiber and micronutrient intake explaining the beneficial effect on in particular LDL cholesterol.

Protein, Amino Acids, and Insulin Secretion

Protein and AA are known to stimulate insulin and glucagon secretion from the pancreas. Insulin stimulates peripheral glucose uptake, in particular in muscle tissue, and hence can lower glucose levels. Indeed, when co-ingested with glucose protein and AA can stimulate insulin secretion, and can attenuate the glucose response, although these effects are relatively small in young healthy adults. The metabolic effects differ per AA, with isoleucine and phenylalanine resulting in the largest attenuation of glucose levels while leucine had the largest impact on insulin secretion when co-ingested with glucose. In type 2 diabetes, where insulin secretion after carbohydrate ingestion is severely impaired, amino acid and protein co-ingestion were shown to substantially increase plasma insulin responses, and can assist in acute metabolic control. Whether this acute stimulatory effect of AA on insulin is conserved over time, as well as whether this is desirable knowing the effect of chronic hyperinsulinemia on worsening of insulin resistance, needs to be established. Next to stimulation of insulin secretion, AA are also known to induce a rise in glucagon and to attenuate the glucose lowering effect of glucagon response, with again a different effect for different AA. Glucagon has multiple metabolic effects. Glucagon opposes insulin and stimulates gluconeogenesis and hepatic glucose output, resulting in maintenance or elevation of plasma glucose levels and availability for peripheral tissues. Elevated fasting glucagon levels (hyperglucagonemia) are present in obese individuals with (pre-)diabetes and are predictive of future diabetes development. The effect of protein and AA on glucagon secretion and circulating glucagon could be one of the mechanism underlying the observation of an increased diabetes risk associated with a high (animal) protein consumption. But glucagon also stimulates insulin secretion which in the prandial state could assist in glycaemic control. In addition glucagon activated hepatic lipolysis which lower hepatic lipids, a condition known to be associated with insulin resistance. Both insulin and glucagon responses are modulated by incretin responses, i.e., gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Nutrients as well as mixed meals trigger incretins, but the endogenous incretins do not seem to play a major role in the hyper glucagon secretion seen after a mixed meal in type 2 diabetes.

Branched-Chain Amino Acids (BCAAs) and Insulin Resistance

Elevated blood BCAA levels have bene identified as predictor of diabetes risk, and direct infusion of BCAA induces rapidly insulin resistance. Elevated BCAA levels are not just a simple reflection of a high protein intake. Next to food intake, also protein breakdown in tissue, a process which is inhibited by insulin, and gut microbial synthesis contribute to BCAA appearance and levels in the blood. Disappearance of BCAA on the other side is a consequence of protein synthesis, excretion and BCAA catabolism. All these processes together define the levels of BCAA in plasma, and in particular a dysfunctional or impaired breakdown of BCAA is thought to be an important factor in the elevated circulating BCAA levels in patients with (pre)diabetes. A direct effect could be the persistent activation of the mTOR pathway. The mTOR pathway is a nutrient-sensing pathway, which integrates nutrient sensing and insulin signalling to coordinate cell growth and metabolism and it could have a crucial role in understanding the association between BCAA and insulin action. BCAA and other nutrients activate mTOR, which is well-known for its role in dietary protein stimulated (muscle) protein synthesis. Indirectly, BCAA, but in particular its potential toxic metabolites, may result in an impaired mitochondrial function, with reduced oxidation of lipid substrates resulting in accumulation of lipid in (muscle) cells. Lipid accumulation in muscle tissue is associated with insulin resistance, as lipid intermediates can interfere with insulin signalling, known as ‘lipotoxicity’, resulting in a reduced insulin stimulated glucose uptake and impaired glucose homeostasis.

Guidelines and Recommendations

Several national bodies have in recent years released guidelines or statements for those with diabetes are at risk for developing diabetes (‘prediabetes’), including the American Diabetes association, ADA, Diabetes Canada, Diabetes UK as well as the Dutch diabetes Federation, NDF. General consensus is that diabetes can be delayed or prevented by a healthy diet and increased physical activity, accompanied by weight loss. Dietary protein intake is not a key target in nutritional guidelines for patients with diabetes across the different countries. According to Nutrition Therapy guidelines of Canada Diabetes Association, there is no evidence that the usual protein intake for most individuals (1 to 1.5 g per kg body weight per day), representing 15 to 20% of total energy intake, needs to be modified for people with diabetes. This level of intake, that is generally observed in western countries, can already considered to be high-protein compared to the 0.8 g/kg BW recommendation of the FAO, although experts recommend an intake of ~1.2 gram/kg BW for older adults. Importantly, this intake in grams per kg per day should be maintained or increased with energy-reduced diets to maintain lean mass during weight-loss.

Risks of Low Protein Diets

Protein is an essential nutrient crucial to growth and development. Your body uses it to form the foundation of your muscles, skin and bones, produce important enzymes and hormones, and build and repair tissues. Studies show that a protein deficiency can have detrimental effects on health, including impaired immune function, muscle loss and decreased growth in children. Other possible symptoms of a protein deficiency include swelling, anemia, fatty liver disease, hair loss and reduced bone density. Besides the possible health risks involved, decreasing your protein intake can be very challenging. Not only does following a low-protein diet take a bit of creativity, it also requires careful planning to ensure you meet your other nutritional needs. This is because high-protein foods supply a good number of calories and key micronutrients. For example, beef is rich in B vitamins, iron and zinc, while beans are a good source of magnesium, phosphorus and potassium. When following a low-protein diet, it’s important to ensure you’re getting these nutrients from other sources to prevent nutrient deficiencies. However, because of its potential dangers and health risks, a low-protein diet is not advisable unless you have an underlying health condition and are under direct medical supervision.

Dietary Considerations for Low Protein Diets

On a low-protein diet, your meals should be focused on the low-protein components of meals, such as grains, vegetables or fruits. You can still include meat and plant-based proteins in your diet, but you should use them as side dishes and consume them only in small amounts. You may also need to bump up your intake of healthy fats, which can provide extra calories to help you meet your daily needs.

Healthy Low-Protein Foods to Include:

Fruits: Apples, bananas, pears, peaches, berries, grapefruit, etc.
Vegetables: Tomatoes, asparagus, peppers, broccoli, leafy greens, etc.
Grains: Rice, oats, bread, pasta, barley, etc.
Healthy fats: Includes avocados, olive oil and coconut oil

High-Protein Foods to Limit or Avoid:

Meats like chicken, turkey, beef and pork
Fish and shellfish
Eggs
Legumes, including beans, peas and lentils
Dairy products like milk, cheese and yogurt
Soy products like tofu, tempeh and natto
Nuts like walnuts, almonds and pistachios
Seeds like chia seeds, flaxseeds and hemp seeds

Low Protein Diet and Mortality in Type 2 Diabetes

In the pooled analysis of two Japanese cohorts, low protein intake was associated with increased mortality in patients with type 2 diabetes mellitus. Significant associations between protein intake and mortality were found, especially in patients aged > 75 years or < 65 years, those with ≥HbA1c 7.5%, or SBP ≥ 135 mmHg, and remained after adjustment for covariates, including albuminuria and renal function. In our study, the association between reduced protein intake and mortality varied with age. When total energy and exercise were corrected, the mortality rate increased as the protein intake decreased in the group with patients aged > 75 years.

Low Protein Diets in Patients with Chronic Kidney Disease

Low-protein diets (LPDs) are often considered as contraindicated in diabetic patients, and are seldom studied. In patients with type 2 diabetes, higher proteinuria was associated with mortality and initiation of dialysis. The definitions of “diabetic nephropathy” and of “proteinuric CKD diabetic patients” identify a younger subset of the diabetic population, with lower comorbidity and higher prevalence of severely reduced kidney function. As a reflection of these differences, patient survival was lower in the older scarcely proteinuric cohort. The time to RRT was shorter in patients with diabetic nephropathy or proteinuria at start of the diet over 1 g/day. Diabetes is more often observed in the context of vascular disease and metabolic syndrome, and is not in keeping with recent observations suggesting that diabetic patients have different CKD progression as compared to non-diabetic patients, or different response to the diet.

Protein Intake and Physical Limitations

A new study conducted by The Ohio State University and Abbott showed that half of the adults surveyed living with diabetes did not consume the daily recommended intake of protein, which is associated with lower diet quality, increased carbohydrate intake, and greater physical limitations. The study highlights protein intake as an essential and often overlooked consideration in meeting the nutritional needs of people living with diabetes and its importance in supporting strength and mobility. Patients with diabetes who did not meet the recommended daily intake of protein had greater physical limitations, which together may suggest an increased risk of muscle loss.

Sample Menu for a Low-Protein Diet

Here’s a three-day sample menu to get you started.

Day 1

Breakfast: 1 boiled egg with 2 cinnamon pancakes.
Snack: 1 medium apple with 1 tbsp (16 grams) peanut butter.
Lunch: 1 cup (140 grams) cooked spaghetti with vegetable Bolognese and 1/2 cup (67 grams) roasted asparagus.
Snack: 1 cup (76 grams) strawberries with 1 ounce (28 grams) dark chocolate.
Dinner: Tortilla wrap with 1 ounce (28 grams) canned tuna and 1/2 avocado. Garnish with tomatoes, lettuce and onions.
Snack: 1 cup (148 grams) frozen blueberries.

Day 2

Breakfast: 1 cup (28 grams) cereal with 1/2 cup (119 ml) almond milk and 1 large orange.
Snack: 1 medium banana.
Lunch: Sandwich with 1 ounce (28 grams) deli meat and 1/2 cup (55 grams) green beans. Garnish with lettuce, tomatoes and mayonnaise.
Snack: 5 crackers with 1 ounce (28 grams) cheddar cheese.
Dinner: 2 ounces (57 grams) grilled chicken with 1/2 cup (90 grams) cooked white rice and 1/2 cup (78 grams) steamed broccoli.
Snack: 1 cup (245 grams) coconut yogurt with 1/2 cup (72 grams) blackberries.

Day 3

Breakfast: 2 slices toast with 1 ounce (28 grams) cream cheese and 1 medium apple.
Snack: 1 cup (151 grams) frozen grapes.
Lunch: Cauliflower burger and 1 small baked sweet potato topped with 1 tablespoon (14 grams) olive oil.
Snack: 1/2 cup (70 grams) baby carrots with 2 tablespoons (30 grams) guacamole.
Dinner: Greek salad with 2 cups (60 grams) spinach and 1 ounce (28 grams) feta cheese. Add cucumbers, tomatoes, olives and onions to taste, top with 1 tbsp (14 grams) olive oil. Serve with 1 slice pita bread.
Snack: 3 cups air-popped popcorn.

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