What You Need to Know About Protein Calorie Malnutrition

Amino Acids

Improper nutrition affects the human population on a global scale. Protein calorie malnutrition, in particular, is a dietary deficiency that has serious repercussions. In this article, we dive into how protein calorie malnutrition is a condition faced by the people of developing and developed countries. Here we go over helpful things to know about protein calorie malnutrition, its causes, complications, who’s at risk, and how to prevent it.

What Is Protein Calorie Malnutrition?

The World Health Organization defines several types of suboptimal nutrition for human functioning. (1) Undernutrition refers to the inadequate intake of energy to support physical needs and often results in weight loss and underdevelopment. Overnutrition is the excessive intake of energy that results in obesity and diet-related diseases. Both nutrient deficiency and nutrient excess can jeopardize normal organ system functions and can raise the risk for certain diseases. It’s important to note that types of malnutrition can overlap; for example, an individual with obesity can have nutrient deficiencies.

Protein calorie malnutrition, also referred to as protein energy malnutrition, describes insufficient protein intake or protein deficiency, and it can be an acute or chronic condition. Marasmus and kwashiorkor are two types of acute protein calorie malnutrition. In some specific cases that show elements of both, doctors may diagnose a patient with marasmic kwashiorkor.

Marasmus develops from an extreme deficiency in energy intake and protein. Nutritional marasmus leads to a loss of muscle and loss of subcutaneous fat, and individuals with marasmus become severely underweight. (2)

Individuals develop kwashiorkor as a result of consuming a restrictive diet based mainly on carbohydrates. Kwashiorkor presents with specific symptoms: (3)

  • Under pigmented hair
  • Hair loss
  • Swelling and fluid retention in limbs
  • Stunted growth
  • Behavioral and mental changes
  • Skin irritation, rashes, and peeling
  • Swollen abdomen
  • Enlarged liver
  • Muscle wasting

Chronic protein calorie malnutrition, though it doesn’t meet the diagnostic criteria for marasmus or kwashiorkor, is still very detrimental. Chronic protein calorie malnutrition causes muscle wasting and impacts growth, cognitive function, physical function, and healing.

We Need Essential Amino Acids

Essential amino acids are the critical compounds that we get from dietary protein. When we consume food, our body breaks down protein into amino acids, which we can then use as raw material to build the proteins that we need. Altogether, there are 20 amino acids that are biochemically necessary for humans. Our bodies are unable to produce nine of these amino acids, which means we must get them from the foods we eat. These nine essential amino acids are histidine, methionine, lysine, leucine, isoleucine, phenylalanine, valine, threonine, and tryptophan.

Nearly All Biological Functions Require Amino Acids

Nearly everything in our body requires amino acids to function. Amino acids are used in the production of neurotransmitters that we require to regulate our emotions and sleep schedule. The liver uses amino acids to regulate metabolic processes that promote healthy insulin function and cholesterol processing. Muscle tissue, including the heart muscle, requires amino acids to rebuild and repair after daily use. The immune system utilizes amino acids to modulate stress response, fight off infections, and heal after an injury. Essential amino acids are an integral part of our everyday functioning. (4)

Essential Amino Acids and Growth

Essential amino acids are crucial for growth and development. During infancy and early childhood, humans are growing and developing at an extremely rapid rate. Within the first 12 months of life, a baby gains up to 3.5 grams of protein mass each day! (5) Without optimal ratios of essential amino acids, this rate of protein synthesis would be unsustainable, which results in stunted growth. In a compelling study assessing 313 Malawi children, findings showed that stunted children had lower blood levels of all nine essential amino acids. (6)

Protein Quality vs. Quantity

In widespread common knowledge of nutritional recommendations, the importance of essential amino acids tends to be overlooked. Recommended protein intake focuses mainly on the total amount of protein consumed throughout the course of the day, and not on the consumption of a comprehensive profile of all essential amino acids. Consuming a smaller amount of protein that provides optimal ratios of all essential amino acids is much healthier than consuming a large quantity of protein that lacks certain essential amino acids.

Protein Digestibility-Corrected Amino Acid Score

The protein digestibility-corrected amino acid score (PDCAAS) is used to assess a food’s completeness of essential amino acid composition and to evaluate how well a protein source can be utilized by humans. Scoring typically ranges from zero (worst protein score) to 100% (best protein score). (7)

The importance of evaluating protein quality over protein intake is proven in scientific literature. In a study conducted at the Friedman School of Nutrition Science and Policy at Tufts University in Boston, Massachusetts, researchers assessed data from 116 countries evaluating stunted growth, protein malnutrition, protein consumption, and adjusted protein quality with PDCAAS. (8) Results revealed that protein quality is a better predictor of risk for protein malnutrition than protein quantity. (8)

Research also shows that the intake of high-quality proteins containing all essential amino acids early in life predicts a healthier weight and height at 10 years of age. (9)

Protein Calorie Malnutrition in the Developing World

The World Health Organization estimates that of the global population of children under 5 years old, 69 million suffer from wasting muscle and fat tissue and 155 million suffer from stunted growth. Estimates also show that 462 million adults worldwide are underweight. (10) Populations in developing countries are at higher risk for severe forms of protein calorie malnutrition and face the greatest risk of mortality from undernutrition.

Without a doubt, protein calorie malnutrition contributes significantly to these numbers. This can be supported by the fact that hundreds of millions of people in sub-Saharan Africa alone rely on maize and cassava as their main sources of food. (11) Maize and cassava have PDCAAS scores of 52 and 57, far from the optimal level needed for the sufficient intake of essential amino acids. (12)

Moreover, research suggests that children growing up in poorer conditions with more susceptibility to infection may have even higher essential amino acid requirements than an average child. Research teams from Canada and India collaborated to evaluate lysine needs among Indian children with intestinal parasites. (13) Results showed that children with a parasitic infection required 20% more lysine than children without a parasitic infection. (13)

Protein Calorie Malnutrition in the United States: It Exists in the Developed World

At one point, protein calorie malnutrition was considered a thing of the past in wealthy, industrialized nations like the United States. Malnutrition is further masked by our country’s obesity epidemic. However, sections of the population are at higher risk for protein calorie malnutrition. This is compounded by the fact that recommended protein intake has historically focused solely on the amount of protein consumed, which casts aside the importance of protein quality.

Protein Malnutrition Among Elderly Adults

Older adults often experience protein deficiency and malnutrition, especially during hospital stays. Statistics show that the rate of malnutrition among hospitalized older adults can be as high as 50%. (14) As humans age, cellular processes that were once efficient begin to slow down. Maintaining muscle mass becomes a concerted effort that requires the combination of consistent activity and proper nutrition.

The biological reality of aging combined with a chronic illness contributes to the large proportion of hospitalized elderly patients with protein malnutrition.

The following are examples of conditions that add to the risk of malnutrition for older adults: (15)

  • Liver cirrhosis and liver damage
  • Psychiatric conditions and cognitive decline
  • Gastrointestinal diseases and infections
  • Kidney disease
  • Heart disease
  • Metabolic syndrome and diabetes
  • Medications that alter appetite

Older adults who live with a chronic illness and protein deficiency are very prone to developing cachexia, which describes the deterioration of muscle. Low muscle mass inhibits healing time and recovery from illnesses which can lead to severe frailty, risk of falling, and lower quality of life.

Protein Calorie Malnutrition in American Children

Malnutrition in American children is a bigger issue than you might guess. Though children in wealthier, developed nations may have fewer externally obvious symptoms of undernutrition, they still experience severe health outcomes that impact their growth and development.

Even though kwashiorkor is rare in the United States, there are documented cases of children with kwashiorkor as a result of severe protein calorie malnutrition.

In other cases, the consequences of protein deficiency are so varied and interconnected across human organ systems that it can be challenging to identify protein calorie malnutrition.

What Are the Risk Factors for Protein Deficiency in Children?

Several factors put American children at risk for protein malnutrition.

1. Conditions that Impact Food Intake and Absorption

Children with chronic illnesses often face appetite suppression or nutrient malabsorption. Gastrointestinal illnesses like Crohn’s disease, celiac disease, or intestinal viral infections result in decreased food intake and nutrient absorption. Other chronic illnesses like cystic fibrosis or congenital heart disease are contributing factors as well. (16)

Hospital stays due to illness or injury exacerbate pediatric malnutrition. Estimates suggest that up to a quarter of hospitalized pediatric patients face protein calorie malnutrition. (17)

Additionally, children who are picky eaters or have food aversions may be at a higher risk for protein deficiency. For example, if a child has strong aversions to foods except starchy foods consisting of simple carbohydrates – such as white bread, pasta, and french fries – he or she is not getting enough of the foods that contain essential amino acids.

2. Strict Diets Without Adequate Protein

With the rising popularity of plant-based diets, the risk of amino acid deficiency is becoming increasingly relevant.

In general, meat and dairy products that have a higher PDCAAS score and provide a complete supply of essential amino acids, in comparison to plant-based products. In many cases, a single animal-based source of protein will provide all necessary amino acids. For example, eggs, milk, and whey protein all have a PDCAAS score of 100. Beef comes in close to that with a score of 92. (18)

In contrast, the main plant-based source of protein with a PDCAAS score of 100 is soy protein. Other plant-based protein sources typically have much lower PDCAAS scores; for example, black beans are scored at 75 and peanuts are scored at 52. (18)

Plant-based diets can be extremely healthy and lower the risk for cardiovascular disease, metabolic syndrome, and a host of other illnesses. Vegan diets can also supply plenty of essential amino acids necessary for growth and development. However, it is critical to eat a varied diet and combine several plant sources of protein throughout your day. Protein malnutrition is imminent when a child subsists on foods like chips, crackers, pasta, and almond milk; though this diet is vegan, it provides nowhere near the necessary ratios of essential amino acids to sustain growth.

A wealth of research backs up the necessity to carefully plan plant-based diets to ensure adequate protein intake.

Infants are particularly vulnerable to protein deficiencies from plant-based diets. A compelling study conducted by a research team at the Department of Human Nutrition at Wageningen Agricultural University in The Netherlands evaluated the protein and nutrient intake of infants following the breastfeeding period. (19) Findings showed that infants on a plant-based diet consumed 20% less than the recommended daily amount of protein. (19) In the United States, cases of kwashiorkor have been documented as a result of replacing milk with plant-based milk alternatives like rice milk. (20)

To support healthy growth and development for children of all ages, vegan diets must be planned accordingly to meet essential amino acid needs. This may require consuming a larger volume of varied plant-based proteins. Research estimates that in order to provide optimal levels of amino acids from plant-based sources, babies need up to 35% higher protein intake, young children need up to 30% higher intake, and children older than 6 need up to 20% high protein intake. (21)

3. Socioeconomic Status and Food Access

Food access and risk for malnutrition are strongly correlated with low socioeconomic status. Approximately 40% of impoverished children face food insecurity in the United States. (22) Food insecurity means that there is limited access to adequate amounts of nutritious foods and unfortunately, it is common among low-income families.

Statistics show that of impoverished children between the ages of 2-6 years old, approximately a third met body mass index (BMI) criteria for categorization as underweight. (2) On top of that, startling statistics show that more than half of American infants are born into low-income families, are at risk for nutrient deficiencies, and rely on support from the Special Supplemental Nutrition Program for Women, Infants, and Children supported by the U.S. Department of Agriculture. (23)

Protein Malnutrition Raises the Risk for Deficiencies in Other Nutrients

If you aren’t eating the right foods to get enough essential amino acids, it’s likely that you are also not getting the foods that also contain essential vitamins, minerals, and antioxidants. This is particularly true on a vegan or vegetarian diet. A healthy plant-based diet that provides plenty of essential amino acids is carefully-planned and varied, with lots of vegetables, fruits, whole grains, nuts, seeds, and legumes.

How to Address Protein-Calorie Malnutrition

1. Raising Awareness

The importance of protein quality over quantity is slowly becoming more mainstream. Starting conversations and discussions with others – including health care providers, physicians, and dietitians- will help address the disconnect between protein intake and protein quality. Increased awareness of which foods contain high-quality protein will help us all make the best food choices possible to ensure the optimal dietary intake of essential amino acids.

2. Supplementing

Incorporating essential amino supplements into your regimen is especially critical when following a vegan or vegetarian diet. While it’s still important to eat a varied diet rich in fruits, vegetables, whole grains, and legumes, taking a high-quality amino acid supplement makes it easier to ensure that you’re getting the essential amino acids you need. As a result, you’ll be relieved of worries around meticulously planning plant-based meals for you or your children with complementary foods that contain all of the necessary amino acids.

3. Supporting Food Programs

Many nonprofit groups across the United States work to provide healthy, nutrient-dense, high-protein foods to those at risk for food insecurity and malnutrition. Many programs also offer nutritional support and nutrition education. Areas of limited access to nutritious foods are referred to as food deserts and can be found in urban, suburban, and rural areas. Making a small donation can go a long way in helping nutrition programs make a difference. When donating to food banks, stick to items like whole grain pasta, canned beans, and canned vegetables instead of sugary processed foods. These small changes can go a long way in fighting protein deficiency and supporting the overall health of fellow citizens. (24)

Are You at Risk for Protein Calorie Malnutrition?

If you think you or a loved one may have protein calorie malnutrition, a health care provider will analyze and integrate information from your medical record, a physical examination, and a nutritional assessment. These will help determine if you have a nutritional deficiency that is negatively impacting your health.


The significance of protein quality is gaining momentum and support as a critical key to addressing the global malnutrition crisis. Adequate amounts of essential amino acids are indispensable to growth, development, and healthy functioning for children and adults around the world.

What Is Protein Calorie Malnutrition?


1. https://www.who.int/news-room/fact-sheets/detail/malnutrition

2. https://emedicine.medscape.com/article/1104623-overview#a6

3. https://www.ncbi.nlm.nih.gov/books/NBK507876/

4. https://www.ncbi.nlm.nih.gov/pubmed/16960159

5. https://www.ncbi.nlm.nih.gov/books/NBK234922/

6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4856740/

7. https://www.ncbi.nlm.nih.gov/pubmed/10867064

8. https://www.ncbi.nlm.nih.gov/pubmed/23107551/

9. https://www.ncbi.nlm.nih.gov/pubmed/26598853

10. https://www.who.int/news-room/fact-sheets/detail/malnutrition

11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5114156/


13. https://www.ncbi.nlm.nih.gov/pubmed/25761501/

14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3396084/

15. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3396084/

16. https://www.ncbi.nlm.nih.gov/pubmed/23528324

17. https://hosppeds.aappublications.org/content/6/1/37.long

18. https://www.ncbi.nlm.nih.gov/pmc/articncbi.nlm.nih.gov/pmc/articles/PMC3905294les/PMC3905294/

19. https://www.ncbi.nlm.nih.gov/pubmed/2544417

20. https://www.ncbi.nlm.nih.gov/pubmed/11346341

21. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2912628/

22. https://pediatrics.aappublications.org/content/pediatrics/137/4/e20160340.full.pdf

23. https://www.fns.usda.gov/wic/about-wic-wic-glance

24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6214863/

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