Protein Malnutrition: Its Clinical Features and Epidemiology (Part 2)

 by: 

lim ju boo BSc, MD, Postgrad Dip Nutrition, MSc, PhD (Med), FRSPH, FRSM 

The Quality of Dietary Protein and the Persistence of Nutritional Deficiency Diseases:

When considering the role of protein in human nutrition, it is crucial to recognize that not just the quantity, but also the quality of protein in our diet profoundly influences health outcomes. Protein quality is determined by its biological value, a measure of how efficiently the body can utilize a protein source based on its amino acid composition.

The Quality of Dietary Protein and the Persistence of Nutritional Deficiency Diseases:

When discussing protein in the context of human nutrition, it is essential to recognize that not only the quantity, but also the quality of protein in the diet plays a critical role in health and development. The biological value (BV) of a protein reflects how efficiently the body can utilize it, which depends largely on its amino acid composition.

For instance, gelatin, although technically a protein, is considered an incomplete protein because it lacks the essential amino acid tryptophan and is significantly deficient in isoleucine, threonine, and methionine. These amino acids are among the most limiting in gelatin, meaning they are present in very low quantities relative to the body’s needs for protein synthesis. As a result, gelatin has a biological value of zero, and a diet based solely on gelatin cannot maintain a positive nitrogen balance or support growth, particularly in children, whose demands for protein are especially high.

As such, a diet consisting solely of gelatin would lead to a zero nitrogen balance, rendering it inadequate for maintaining body protein levels or supporting growth, especially in children whose anabolic needs are high.

Similarly, children consuming a diet primarily based on maize (corn) may still suffer from protein deficiency diseases, despite seemingly adequate caloric intake. This is because lysine, an essential amino acid, is deficient in maize. As a limiting amino acid, its low availability restricts the body’s ability to synthesize complete proteins, leading to conditions such as kwashiorkor.

Kwashiorkor and Marasmus: 

Two Faces of Protein-Energy Malnutrition

Despite medical advancements and global nutrition efforts, kwashiorkor and marasmus continue to afflict vulnerable populations, especially in developing countries and food-insecure regions. These conditions predominantly affect infants and young children, often with devastating consequences if left untreated.

Kwashiorkor:

Kwashiorkor is characterized by protein deficiency despite adequate or high caloric intake, typically from carbohydrates such as cassava, rice, or maize. It usually manifests in children aged 3 to 5 years and presents with distinctive features including:

1. Edema (swelling due to fluid retention)
2. Dermatitis and skin lesions
3. Hair discoloration and thinning
4. Hepatomegaly (enlarged liver with fatty infiltration)
5. Lethargy and irritability

Kwashiorkor is prevalent in regions where protein-rich foods are scarce, including:

1. The Democratic Republic of Congo (DRC)

2. Malawi, Zambia, and Haiti

3. Rural and impoverished communities across sub-Saharan Africa

Marasmus:

In contrast, marasmus results from a severe deficiency in both protein and total caloric intake. It is essentially a state of starvation and affects individuals of all ages, though it is most commonly seen in infants and young children. Clinical features include:

1. Severe wasting and emaciation

2. Stunted growth

3. Loss of subcutaneous fat
4. Extreme thinness with visible bones
5. Increased susceptibility to infections

Marasmus is frequently reported in regions afflicted by drought, famine, conflict, and chronic poverty, including:

Somalia, Niger, Cameroon, Pakistan, Sudan, and parts of the Horn of Africa

Malnutrition in Malaysia: A Hidden Concern

Although Malaysia is considered a relatively developed nation, undernutrition and malnutrition remain public health concerns, especially among children under the age of five. While kwashiorkor and marasmus are not widespread, isolated cases continue to be reported, primarily among disadvantaged or rural populations.

National health surveys and studies indicate notable rates of:

1. Stunting (low height for age)
Wasting (low weight for height)

2. Underweight (low weight for age)

These forms of undernutrition reflect broader socio-economic and nutritional challenges, including:

Poverty and food insecurity

Inadequate breastfeeding and poor weaning practices
Limited access to high-quality, protein-rich foods
Nutritional unawareness among caregivers

Despite various government and NGO interventions, persistent gaps in nutrition education, maternal health, and childhood feeding practices contribute to these outcomes.

Pellagra: The Niacin Deficiency Disease

Another nutritional disorder that continues to afflict certain populations is pellagra, a disease caused by a deficiency of niacin (vitamin B₃) or its metabolic precursor tryptophan. Pellagra is classically associated with the "three Ds": Dermatitis, Diarrhea, and Dementia, and, if left untreated, may lead to death.

Dietary Cause:

Pellagra typically arises in populations whose diet relies heavily on unprocessed maize, which is deficient in both niacin and tryptophan. Furthermore, niacin in maize is bound and not bioavailable unless the corn undergoes a process called nixtamalization (treatment with alkaline lime water), which is not common in many cultures.

Regions Still Affected:

Despite being largely eradicated in developed nations due to food fortification and diet diversification, pellagra remains a concern in parts of:

Sub-Saharan Africa (where maize is a staple and diets lack diversity), India, especially in regions reliant on jowar (Sorghum vulgare), China, particularly along river delta areas, refugee camps, where individuals may depend on food rations lacking sufficient niacin or protein

Historically, pellagra was a major public health issue in the American South during the early 20th century, but has since been controlled through the fortification of cereals and grains.

Conclusion

Malnutrition remains a complex and multifactorial global health challenge, influenced not only by food availability, but also by the nutritional quality of that food. Protein-energy malnutrition disorders such as kwashiorkor, marasmus, and pellagra illustrate the critical need for balanced diets that provide not only calories but also essential amino acids, vitamins, and minerals.

Even in countries like Malaysia, where food is generally available, issues like economic disparity, cultural dietary habits, and lack of nutrition education can result in hidden hunger and micronutrient deficiencies, especially among children. Addressing these problems requires comprehensive public health strategies, nutritional surveillance, and community-level interventions to ensure all individuals receive the nutrients necessary for optimal growth, development, and health.

References:

 1. Young, V. R., & Pellett, P. L. (1994). Plant proteins in relation to human protein and amino acid nutrition. American Journal of Clinical Nutrition, 59(5 Suppl), 1203S–1212S.

2. Gelatin amino acid composition: U.S. Department of Agriculture (USDA) FoodData Central.  

3. Müller, O., & Krawinkel, M. (2005). Malnutrition and health in developing countries. Canadian Medical Association Journal, 173(3), 279–286.

4. Black, R. E., et al. (2008). Maternal and child undernutrition: global and regional exposures and health consequences. The Lancet, 371(9608), 243–260.  

5. Institute for Public Health (2022). National Health and Morbidity Survey (NHMS 2022): Maternal and Child Health. Ministry of Health Malaysia.

6. Hegyi, J., Schwartz, R. A., & Hegyi, V. (2004). Pellagra: dermatitis, dementia, and diarrhea. International Journal of Dermatology, 43(1), 1–5.

7. World Health Organization (WHO). Micronutrient deficiencies: Niacin (Vitamin B3).  

8. Black, R. E., et al. (2008). Maternal and child undernutrition: global and regional exposures and health consequences. Lancet, 371(9608): 243–260.

9. Müller, O., & Krawinkel, M. (2005). Malnutrition and health in developing countries. CMAJ, 173(3): 279–286.

10. Hegyi, J., Schwartz, R. A., & Hegyi, V. (2004). Pellagra: dermatitis, dementia, and diarrhea. Int J Dermatol, 43(1): 1–5.

11. National Health and Morbidity Survey (NHMS 2022). Ministry of Health Malaysia.

12. World Health Organization (WHO). Micronutrient Deficiencies – Niacin.

13.  U.S. Department of Agriculture (USDA). FoodData Central – Gelatin (unflavored) amino acid composition.