A low-protein diet may be recommended for individuals with kidney-related disorders, such as chronic kidney disease (CKD) or phenylketonuria. This dietary approach involves reducing the intake of high-protein foods and emphasizing fruits, vegetables, and healthy fats. By making key changes, a person can develop a satisfying and diverse low protein diet plan that works for them.
Understanding the Need for a Low-Protein Diet
When the body digests protein, it produces a waste product called urea. In individuals with impaired kidney function, urea can accumulate in the blood, leading to fatigue and loss of appetite. A low-protein diet aims to reduce the workload on the kidneys, preventing the buildup of urea and alleviating these symptoms.
Protein is needed for growth, upkeep, and repair of all parts of your body. When your body digests it, a waste product called urea is produced. If the kidneys are not working well, urea can build up in the bloodstream and may cause loss of appetite and fatigue. Eating a low-protein diet will reduce the workload on the kidneys so that the remaining healthy part of the kidney does not have to work so hard.
Who Might Benefit from a Low-Protein Diet?
A doctor may recommend a low-protein diet for the following conditions:
Chronic Kidney Disease (CKD): By reducing protein intake, people with CKD who are not on dialysis can reduce stress on their kidneys and prevent the buildup of urea in the bloodstream. A 2018 review of 17 studies reports that very low protein intake may slow down the progression of advanced kidney failure.
Read also: Protein Coffee Smoothie Recipe
Diabetic Neuropathy: A 2019 article found that a low protein diet may improve diabetic neuropathy. However, 2018 research suggests that there is no significant association between a low protein diet and renal function improvement in people with diabetic neuropathy. More research is necessary.
Phenylketonuria (PKU): PKU is a rare disorder that occurs when the body does not produce the enzyme needed to break down an amino acid called phenylalanine. Amino acids are the building blocks of protein. The main treatment for PKU is a lifelong low protein diet.
Homocystinuria: Homocystinuria is an inherited disorder that affects the body’s ability to process methionine, another amino acid. A buildup of methionine causes problems with vision and bone health. A low protein diet can help treat the condition.
Authors of a 2016 review of research suggest that a low protein diet may also provide some benefits for people without kidney problems. They report that in middle-aged, but not older, adults, restricting protein intake may reduce the risk of:
- Cancer
- Diabetes
- Heart disease
Some 2018 research indicates that a diet low in protein and high in carbohydrates may help protect brain health and reduce cognitive decline. However, the scientists conducted this research only in mice and cannot be sure of the effects on humans.
Read also: Wound Healing: The Protein Connection
Foods to Include and Avoid
Low-Protein Foods
A person following a low protein diet can get most of their calories from the foods below, which are relatively low in protein.
The following are examples of low protein foods and drinks:
- Fruits such as apples and grapes
- Vegetables such as:
- Carrots
- Celery
- Mushrooms
- Onions
- Parsley
- Bell peppers
- Bouillon or broth
- Mustard
- Tomato juice
- Orange juice
Many other types of food and drinks are low in protein, and a person should use moderation when incorporating them into the diet. Some of these foods include:
- Sugar
- Tea and coffee, without dairy milk
- Sorbet
- Margarine
Moderate-Protein Foods
On a low protein diet, people should eat foods that contain moderate amounts of protein sparingly. Examples include:
- Bread
- Crackers
- Breakfast cereals
- Pasta
- Oats
- Corn
- Rice
Low protein versions of many of these products are available online or in grocery stores.
Read also: The ultimate guide to protein coffee benefits.
High-Protein Foods to Limit or Avoid
Protein is an essential nutrient, so even people on a low-protein diet need to consume a certain amount of protein to stay healthy. However, high protein foods should make up only a small part of the daily caloric intake.
Anyone on a low protein diet should limit or avoid the consumption of the following:
- Meat
- Poultry
- Fish
- Eggs
- Dairy, including milk, cream, and cheese
- Beans, peas, and lentils
- Soy foods, such as tofu and tempeh
- Seeds and nuts, such as sunflower seeds, peanuts, and almonds
Plant-based dairy alternatives often contain less protein. Some people cannot tolerate high levels of protein. If the body cannot process protein or its waste, these substances build up and cause symptoms ranging from nausea and vomiting to brain damage. For these people, following a low protein diet will reduce the risk of negative health effects.
Structuring a Low-Protein Meal Plan
When following a low protein diet, it can be helpful to think of vegetables and grains as the main components of a meal. A person should consider meat, pulses, and soy products to be side dishes or condiments.
Examples of satisfying low protein meals include:
- A sandwich with very thinly sliced meat and lots of vegetables, such as cucumber and lettuce
- Low protein rice with vegetables and a small portion of meat, tofu, or shellfish
- Low protein pasta with tomato paste and roasted vegetables
- A burrito, made with a low protein tortilla, vegetables, salsa, and homemade guacamole
- Vegetable curry with low protein rice
- Homemade vegetable soup
Low protein snacks include:
- Fresh fruit
- Raw vegetable sticks with salsa or homemade guacamole
- Homemade muffins, made with a low protein baking mix
- A fruit smoothie made with water or a low protein dairy alternative, such as rice milk
- Homemade fruit juice popsicles
Here are some other strategies for keeping protein levels low without compromising on flavor:
- Use unsweetened rice milk or another low protein milk substitute in recipes that call for dairy milk.
- Bulk up soups with small amounts of rice or pasta.
- Increase the vegetable content while decreasing the meat content in recipes. For example, diced mushrooms can be a good meat alternative when cooking spaghetti.
- Add a small amount of egg to salads to make them more filling.
- Top meals with a little Parmesan cheese to increase the flavor without adding too much protein.
- Make a meal more filling by adding some healthful fats.
- When grocery shopping, always check labels carefully for protein contents and ingredients.
Stretching Protein in Recipes
You can "extend" protein in recipes so that a small amount seems more satisfying.
- Sandwiches:
- Use thinly sliced meats - it looks like more.
- Fill out sandwiches with lettuce, alfalfa sprouts, cucumber, chopped celery, apple, parsley or water chestnuts.
- Soups:
- Use lower protein foods such as milk substitutes for cream soups, or rice or pasta to make soups more filling without using too much protein.
- Main Dishes:
- Think of vegetables and grains as the "main dish" and meat as the "side dish" or complement to your meal.
- Try kebabs, using small pieces of meat and more vegetables.
- Make fried rice with vegetables and less meat or shrimp.
- Toss together a chef's salad using crisp vegetables and small strips of meat and egg.
- When making casseroles, decrease the amount of meat; increase the starch, pasta or rice and use low sodium soups when the recipe calls for soup.
- Add low-protein pastas and breads to keep protein within limits.
- Use stronger-tasting cheeses such as sharp cheddar, parmesan or romano - you'll need much less to get the same amount of flavor.
Calorie Boosters
When you lower the amount of protein in your diet, you may also find the calories are lower. It is especially important to get enough calories to maintain a healthy weight at this time. In order to make up those extra calories, try some of these suggestions:
- Increase heart-healthy fats: polyunsaturated vegetable oils (made with corn, cottonseed, safflower, soybean or sunflower oils), olive oil, mayonnaise-type salad dressings.
- Use candy and sweeteners: hard candy, gum drops, jelly beans, marshmallows, honey, jam and jelly, and sugar (if you are diabetic, consult your dietitian).
- Use canned or frozen fruits in heavy syrup.
Potential Benefits of Protein Restriction in CKD
For several decades low protein diets have been proposed for participants with CKD with the aim of slowing the progression to end‐stage kidney disease (ESKD) and delaying the onset of renal replacement therapy. Protein-restricted diets are thought to have nutritional benefits in patients with CKD, particularly in correcting metabolic acidosis and reducing the adverse effects of phosphate and sodium retention.
Experimental studies in rats have shown that loss of nephrons leads to increased glomerular filtration in the remaining nephrons. The compensatory hyperfiltration results from increased plasma flow rates and increasing hydraulic pressure in the remaining nephrons. Eventually these haemodynamic changes lead to increased glomerular permeability with proteinuria and the development of progressive glomerulosclerosis. Long‐term studies in rats have demonstrated that compared with rats with CKD on a high protein diet, rats with CKD on a low protein diet had fewer sclerotic glomeruli and less proteinuria. These experimental data supported the view that protein restriction in people with CKD could protect glomeruli from progressive glomerulosclerosis, slow the deterioration in kidney function and delay the onset of ESKD.
A very low protein intake compared with a low protein intake probably made little or no difference to death. However it probably reduces the number who reach ESKD. In people with advanced kidney failure, a very low protein intake probably slows the progress to kidney failure.
Potential Risks and Considerations
As protein is vital for health, it is important to consult a doctor or dietitian before restricting protein consumption to below 10% of the daily calorie intake. Typically, people should only restrict their protein intake to this extent when a doctor advises them to do so.
Following a low protein diet requires careful planning. Otherwise, it could lead to nutritional deficiencies and other health issues, including muscle loss and poor immune function. Also, protein restriction is not suitable for everyone. For example, older adults may need extra protein, due to the muscle wastage associated with advancing age.
A person on a low protein diet may need to take certain supplements to stay healthy. Vitamin B12, for example, is only present in animal products and fortified foods. Discuss the use of supplements with a doctor or dietitian before beginning a low protein diet. The doctor may also recommend regular follow-up appointments when following a low protein diet.
Working with Healthcare Professionals
Anyone considering a low protein diet should consult their doctor first. The doctor can advise on how much protein to aim for based on individual circumstances. Ask your health care provider to refer you to a registered dietitian to help you with your diet for kidney disease. Some dietitians specialize in kidney diets. Your dietitian can also help you create a diet to fit your other health needs.