What Is Protein Deficiency


Protein is a highly available food source in high-income countries, whereas it is not as available in the diets of those in low-income and some middle-income regions. However, protein deficiency is prevalent within all regions. The effects of protein deficiency reduce the quality of life and even cause mortality. Therefore, protein deficiency should be taken into consideration very precisely. The symptoms should be considered very serious, and treatment options should be applied. Moreover, the sufficiency of plant-based diets is a controversial issue because the fieldwork based on tackling protein malnutrition showed a positive outcome in diet plans based on animal-sourced protein diets. 

What is protein deficiency?

Protein deficiency is simply the lack of adequate protein levels in our body. Consuming an appropriate amount of protein is highly critical for maintaining health, healthy growth, development and normal function from birth to old age.1 Moreover, the importance of proteins is further explained by the studies in which they have removed essential proteins from people's diets.2 Those studies confirmed a lack of balance, low appetite, and extreme fatigue in humans. Furthermore, protein deficiency can cause nervous system defects, metabolic problems, organ failure, and even death.3

Role of proteins in our body

Protein is the main building block of tissues of humans and animals.2 The proteins are converted into small units known as amino acids(AA). To be able to get the benefits of the proteins in our body, they require to be converted into AAs first. Amino acids are the fuel for nitrogen, hydrocarbon skeletons, and sulfur. Only, AAs can provide those resources, and other nutrients cannot replace proteins in that case.

In general, we can divide the roles of proteins into 4 main categories:

Biochemical Function: In that case, proteins play a role as enzymes. Enzymes carry out reactions in our body, such as metabolic reactions for digestion or energy creation. Enzymes are also important in our cellular system for energy production and a fully functioning body. 

Structural Roles: They form the foundation of cells and tissues by being used as structural elements. 

Kinetic Functions: Proteins have roles associated with movement. For example, motor proteins are the carrier proteins that transport molecules inside of the cell or from inside/outside the cell. Moreover, they have actions in skeletal muscles that help the body move.

Channel Proteins: They are located on the cell membrane, which is a thin layer surrounding the cells and serves as a channel for the movement of particles in and out of the cell.

Our body requires proteins to create DNA molecules, our intestine requires proteins for energy to carry out digestion, and our immune system requires proteins for ATP formation, which is the energy unit of the body that protects us.2 Therefore, they are highly critical components of our body. 

Which amino acids does our body require?

There are 20 amino acids used by our body, and they can be divided into 3 main groups. The first one is the “non-essential” amino acids, which can be either taken by the food or produced naturally within the body. The second one is the “conditionally essential” amino acids, which are produced in the body as long as there is no starving or metabolic disorder. The final one is the “essential” group, which is vital for making molecules and hormones and is required to be taken as the nutritional protein because they are not produced naturally in the body.3

Non-Essential Amino Acids:

  • Alanine
  • Asparagine
  • Aspartic acid 
  • Glutamic acid 
  • Serine

Conditionally Essential Amino Acids:

  • Arginine
  • Cysteine 
  • Glutamine
  • Glycine
  • Proline
  • Tyrosine

Essential Amino Acids:

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

What are the causes of protein deficiency?

The insufficient amount of protein intake is the principal factor of protein deficiency. However, there can be other reasons responsible for the protein deficiency. 

In low-income countries, children cannot take enough protein-rich diets. Elderly people and cancer patients have increased protein catabolism and decreased protein intake. People with metabolic defects cannot digest proteins into amino acids. On the other hand, there are health conditions which prevent absorption of proteins into the body tool.

What are the signs and symptoms of protein deficiency?


Nails can change colour into black or white tones. They can also be soft, dry, weak, and easily breakable. Moreover, another condition is observed on the nails as paired, narrow white transverse bands.4 These are all the signs of protein deficiency.


Kwashiorkor is a condition associated with skeletal and mental development, muscular wasting, fatty liver and oedema. This condition is severe and occurs in children with protein deficiency. The symptoms appear with Kwashiorkor and are related to protein deficiency.4


Feeling weakness due to reduced muscles as well as weight loss.5

Impaired mental health 

In the young population, cognitive impairment is a sign of protein deficiency.5 In the general population, protein deficiency symptoms involve sadness, stress and surliness. 

Weakened immune system

Proteins are utilized to create antibodies, which are the fighter molecules of the pathogens. Therefore, in case of protein deficiency, antibodies cannot be produced, and infections increase as a sign of a protein-deficient body.

What are the results of protein malnutrition on our health?

The consequences of the protein deficiency can be as serious as causing death. Therefore, it should be seriously taken into consideration. To provide examples of the underlying health conditions coming with protein insufficiency, cardiovascular problems, hypertension, cardiac failure, anaemia (lack of enough blood) and reduced oxygen transport.2 These all arise due to organ failure, organ system failure and lack of tissue repair as proteins are used as energy, building units, enzymes and molecules for the full functioning of the body, as mentioned above.

Moreover, the neurotransmitter production is also altered, and this has a serious effect on the nervous system, which results in emotional disorders.2

The libido is also lowered by protein deficiency, and even embryonic miscarriage is monitored during pregnancy.2

How to diagnose protein deficiency?

There are guidelines which can be applied to diagnose all types of malnutrition including protein deficiency too. These can be divided into 5 main categories:6

  • History and Examination
  • Disease Status
  • Functional Assessment
  • Laboratory Tests
  • Fluid Balance
  • History and Examination

This will be the main evaluation of the person's specific condition. Questions regarding weight loss, appetite, gastrointestinal symptoms, fever, and medical and drug history can be directed to the person. Weight should be scaled, and Body Mass Index, which is the calculation of the weight against height to determine whether the person is at ideal weight or not, should also be done. 

  • Disease Status

For this case, measurements are carried out for temperature, pulse rate and blood pressure. The presence of wounds should also be evaluated since protein malnutrition prevents tissue repairs and blood clots. 

  • Functional Assessment

Aberrations in mental and physical functions are determined by functional assessments. Mental scoring systems such as POMPs can be used to determine the level of mood, and physical examination of muscles can also be measured by hand dynamometer device. 

  • Laboratory Tests

Laboratory tests are carried out using the blood serum to check inflammation, full blood count, albumin and C-reactive protein levels. Those tests also give insights into the disease status.

  • Fluid Balance

This is for dehydration and oedema analysis. The levels of creatinine, urea, and electrolyte in blood serum will give indicators about the current condition.

How to Prevent and Treat Protein Deficiency? 

First of all, a well-balanced diet is required to prevent protein deficiency. A protein-rich diet should be strictly followed. In situations where the body does not store or digest the protein due to medical conditions, additional supplements to help maintain protein levels should be taken. In developing countries where children are prone to protein malnutrition, more actions are demanded to increase funding, and establish and expand feeding programmes to prevent inequalities for those children in need.

Globally, there are some food groups, such as corn beans and animal-based products, such as milk, which have been applied to children and successfully helped improve their protein deficiency condition. Meat increased growth and cognitive behaviour, whereas animal protein supplements developed the upper arm muscles of Kenyan children.2

In another study, it has been indicated that the diet of the elderly population should contain 65%< to prevent protein deficiency.2

After putting these together, it can be suggested that plant-based diets without animal-sourced products will not be enough to prevent protein deficiency and its side effects. 


Not having adequate amounts of protein can be highly life-threatening and everyone should be aware of its importance. The symptoms are very important in the prevention of severe side effects of protein deficiency. The recognition of the situation and precautionary measures can prevent growth defects in children and give them a healthier future with longer life expectancy. For this aim, more actions, funding, and humanitarian projects are required, especially for low-income and developing countries.  


  1. Carbone JW, Pasiakos SM. Dietary Protein and Muscle Mass: Translating Science to Application and Health Benefit. Nutrients [Internet]. 2019 May 22;11(5):1136. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6566799/ 
  2. Wu G. Dietary protein intake and human health. Food & Function [Internet]. 2016;7(3):1251–65. Available from: https://pubs.rsc.org/en/content/articlelanding/2016/FO/C5FO01530H 
  3. LaPelusa A, Kaushik R. Physiology, Proteins [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555990/ 
  4. Sheth P. Nails in nutritional deficiencies [Internet]. Indian Journal of Dermatology, Venereology and Leprology. 2012. Available from: https://ijdvl.com/nails-in-nutritional-deficiencies/
  5. Khan A. Health complications caused by protein deficiency. Journal of Food Science and Nutrition [Internet]. 2017;01(01). Available from: https://www.alliedacademies.org/articles/health-complication-caused-by-protein-deficiency.pdf 
  6. Barendregt K, Soeters PB, Allison SP, Kondrup J. Basic concepts in nutrition: Diagnosis of malnutrition – Screening and assessment. e-SPEN, the European e-Journal of Clinical Nutrition and Metabolism. 2008 Jun;3(3):e121–5.
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Selun Ilseven

Masters of Cancer Research and Precision Oncology- MSc, University of Glasgow, Scotland.

Selun, with a robust foundation in genetics, cancer research, and precision oncology, she combines her extensive scientific knowledge with years of expertise in science writing, communication, and managing scientific societies.

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