The Effects of Protein Deficiency

The Importance of Amino Acids


Verywell / Alexandra Shytsman

Protein deficiency is a generalized term that can refer to several different conditions. In a clinical setting, protein deficiency is called protein-energy undernutrition (PEU) or protein-energy malnutrition (PEM). It occurs when there is a deficiency in all macronutrients. PEU is not common in the United States, but it is prevalent in Africa and south-central Asia.

There are also genetic conditions—including protein C deficiency and protein S deficiency—that cause problems with proper blood clotting. But when many people discuss protein deficiency in casual conversation, they are usually not referring to a clinical or life-threatening diagnosis, but rather a lack of protein in their day-to-day diet.

Some people may use the term "protein deficiency" when they are simply referring to a lower-than-recommended intake of dietary protein. However, most Americans consume enough protein to meet generalized nutrition guidelines.

Protein and Amino Acids

Low protein intake can have health implications because it deprives your body of amino acids. When digested, protein breaks down into amino acids that help your body to build and grow. While recommended dietary guidelines provide "protein" requirements, our bodies actually need amino acids.

There are 20 total amino acids comprised of nine essential amino acids and 11 non-essential amino acids. Essential amino acids are "essential" in that they must be consumed through the diet because our bodies cannot make them. The nine essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Unlike carbohydrate and fat, there is no mechanism to store excess amino acids that are consumed in the diet. So a continuous supply of amino acids is needed. If you don't get enough protein—or amino acids—your health may be compromised to some degree.

Lack of Protein vs. Protein Deficiency

The extent to which an amino acid or protein shortage affects you may depend on the degree of deficiency. A shortage or lack of protein is different from a true protein deficiency as defined in clinical settings.

What Is Protein Deficiency?

True protein deficiency is effectively non-existent in the United States and other developed countries, says David L. Katz, MD, MPH, FACPM, FACP, founder, and director of the True Health Initiative. But the condition does exist in underdeveloped countries, and it is the leading cause of death among children under the age of 5 worldwide.

There are two types of primary protein malnutrition:

  • Kwashiorkor: This is considered the "wet form" of protein-energy undernutrition (PEU) because edema (swelling) is involved. Other symptoms include muscle atrophy and maintenance or gain of body fat. Kwashiorkor usually occurs in children.
  • Marasmus: This condition occurs when there is a deficiency in all macro and micronutrients. Considered the "dry form" of PEU, it is the more common form of protein deficiency. It causes severe weight loss and depletion of fat and muscle.

Secondary protein deficiency can also be caused by certain medical conditions such as wasting disorders (including AIDS, cancer, or COPD), some gastrointestinal conditions, and illnesses that increase metabolic demands such as infections, trauma, or surgery. Fasting or an eating disorder such as anorexia nervosa can also cause protein deficiency.

What Is Lack of Protein?

Since America is far from starving, true protein deficiency is almost impossible. But according to a study published in the Annals of the New York Academy of Sciences, approximately one billion people worldwide have inadequate protein intake.

Inadequate protein intake would mean we are eating less protein than your body needs, according to Caroline Passerrello, MS, RDN, LDN, spokesperson for the Academy of Nutrition and Dietetics. Since your body requires a sufficient amount of protein, not getting enough may have health implications.

Current USDA dietary guidelines recommend that adults should consume between 10% and 35% of daily calories from protein. But some researchers even believe that current protein recommendations may be too low and should be reconsidered.

Some studies suggest that most Americans consume about 14% to 16% of their daily calories from protein.

Effects of Inadequate Protein

Inadequate protein intake can occur when you’re not eating enough protein to maintain normal body function. Protein is especially important as we age. Approximately one-third of adults over age 50 are failing to meet the recommended daily allowance (RDA) for protein intake according to research.

But older individuals are not the only ones at risk. People following a restrictive diet can also become protein deficient. Additionally, some athletes in weight class sports like boxing, wrestling, and bodybuilding may use self-starvation methods to get lean, leaving them nutrient-deficient.


When protein is lacking in your diet, especially for long periods of time, it can cause deficiencies and potentially lead to adverse effects. Passerrello indicates that inadequate protein can lead to the following conditions:

  • Infections: Your immune system functions best with adequate protein intake. Without a healthy immune system, your risk of infection is increased and the ability to fight off infection is decreased.
  • Muscle wasting: Protein is essential for muscle growth, strength, and repair. Insufficient protein in your diet reduces lean body mass, muscle strength, and function. Not consuming enough protein can also cause muscle cramping, weakness, and soreness. Your body will take protein from muscle tissue and use it as energy to support other vital body functions when protein is low. This eventually causes muscle wasting or atrophy as a direct result of chronic, low dietary protein.
  • Poor wound healing: Wound healing is dependent on good nutrition, including protein intake. Protein deficiency has shown to contribute to low wound healing rates and reduced collagen formation, according to research. Without adequate protein, the wound healing process is said to be greatly compromised.

Studies have also shown that inadequate protein intake has been associated with other conditions including negative adaptations to exercise, reduced bone and calcium homeostasis, electrolyte imbalance, and enzyme production.

This is why adequate protein intake is essential for you to maintain proper body function. Going a step further, understanding the role of protein and ensuring adequate intake in your diet is important.

How to Get Enough Protein

In order to maintain a steady flow of amino acids, adequate protein intake is essential. This doesn’t mean more is better, nor does it mean eating extra protein only builds muscle and not body fat, according to Dr. Katz. What is recommended is eating enough protein to support your body cells, structure, and function. This requirement will be different for each person based on factors like age, sex, and physical activity levels.

Smart Protein Sources

Protein is available in a wide variety of animal and plant foods. Choosing nutritious protein sources is also recommended for optimal health and fitness. Passerrello recommends the following:

  • Aim for meals to have approximately 20 grams of protein and snacks to have about 10 grams of protein. (For reference, 3 ounces of cooked chicken breast has about 21 grams of protein.)
  • Eat higher protein grains like quinoa.
  • Select bean-based noodles instead of wheat-based pasta.

6 Tips for Getting More Protein in Your Diet

The following protein selection tips from the USDA may also be helpful:

  • Avoid fresh chicken, turkey, and pork that have been enhanced with a salt-containing solution.
  • Choose lean or low-fat meat and poultry.
  • Choose unsalted nuts and seeds to keep sodium intake.
  • Select seafood high in omega-3 fatty acids including salmon, trout, sardines, and anchovies.

In general, 1 ounce of meat, poultry, or fish; 1/4 cup cooked beans; one egg; 1 tablespoon of peanut butter; or 1/2 ounce of nuts or seeds can be considered a 1 ounce-equivalent from the Protein Foods Group.

Plant-Based Diets

Eating a plant-based diet has become more popular. Several studies have indicated plant-based diets provide numerous health benefits. One of the most common myths of vegetarian or plant-based eating is that you’re unable to get enough protein in your diet. But according to the Academy of Nutrition and Dietetics, plant-based or vegetarian diets can be nutritionally sound and adequate for all individuals, including athletes.

The following is a great list of plant-based protein sources to include in your diet:

  • Almonds
  • Black beans
  • Lentils
  • Oats
  • Pumpkin seeds
  • Quinoa
  • Tofu

A Word From Verywell

Protein is essential for all cells and body tissue and when in short supply can impair body function. While true protein deficiency is rare in the United States, it exists for some at marginal levels, and some people will benefit from increasing their protein intake. Thankfully, adding protein to your diet is simple and can be achieved by incorporating a wide variety of foods from either plant or animal sources.

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Article Sources
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