Background
The World Health Organization (WHO) defines malnutrition as "deficiencies, excesses or imbalances in a person's intake of energy and/or nutrients." [1] The term covers three broad groups of conditions:
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Undernutrition - Includes wasting, stunting, and underweight
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Micronutrient-related malnutrition - Includes micronutrient deficiencies or excesses
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Overweight, obesity, and diet-related noncommunicable diseases, such as heart disease and type 2 diabetes mellitus
The American Society for Parenteral and Enteral Nutrition (ASPEN) workgroup defines pediatric malnutrition (undernutrition) as "an imbalance between nutrient requirement and intake, resulting in cumulative deficits of energy, protein, or micronutrients that may negatively affect growth, development, and other relevant outcomes." [2]
Women and young children are the most adversely affected groups. From 10% to 20% of women of reproductive age in sub-Saharan Africa and South Asia are underweight, which contributes to the number of low birth weight infants born annually. [3, 4, 5]
Globally, malnutrition is an important risk factor for illness and death, contributing to nearly half of deaths worldwide in children aged younger than 5 years. [1, 6] Protein-energy malnutrition (PEM) is observed most frequently in developing countries but has been described with increasing frequency in hospitalized and chronically ill children in the United States. [7, 8]
Consensus guidelines address malnutrition irrespective of etiology. ASPEN identified two alternative ways to diagnose malnutrition: body mass index (BMI) and unintentional weight loss. Among the various guidelines, the Subjective Global Assessment (SGA) is a highly validated tool that includes medical history and a physical assessment. [9] The main classification of malnutrition is either illness based (severe or moderate) or non–illness based (severe to moderate). [10]
The effect of changing environmental conditions in increasing malnutrition is multifactorial. Poor environmental conditions may increase insect and protozoal infections and also contribute to environmental deficiencies in micronutrients. Overpopulation, more commonly seen in developing countries, can reduce food production, leading to inadequate food intake or intake of foods of poor nutritional quality. Conversely, the effects of malnutrition on individuals can create and maintain poverty, which can further hamper economic and social development. [6]
Kwashiorkor and marasmus are two forms of PEM that have been described, but there has been a paradigm shift in diagnosing pediatric malnutrition. The schema for defining malnutrition incorporates the concepts of chronicity, etiology, and pathogenesis of malnutrition; its relationship with inflammation; and its impact on functional outcomes. [2]
The distinction between the two forms of PEM is based on the presence of edema (kwashiorkor) or absence of edema (marasmus). Marasmus involves inadequate intake of protein and calories, whereas a child with kwashiorkor has fair-to-normal calorie intake with inadequate protein intake. Although significant clinical differences between kwashiorkor and marasmus are noted, some studies suggest that marasmus represents an adaptation to starvation, whereas kwashiorkor represents a dysadaptation to starvation. See the image below.
This infant presented with symptoms indicative of Kwashiorkor, a dietary protein deficiency. Note the angular stomatitis indicative of an accompanying Vitamin B deficiency as well. Image courtesy of the Centers for Disease Control and Prevention.
In addition to PEM, children may be affected by micronutrient deficiencies, which also have a detrimental effect on growth and development. The most common and clinically significant micronutrient deficiencies in children and child-bearing women throughout the world include deficiencies of iron, iodine, zinc, and vitamin A, which are estimated to affect as many as 2 billion people. Although fortification programs have helped diminish deficiencies of iodine and vitamin A in individuals in the United States, these deficiencies remain a significant cause of morbidity in developing countries, whereas deficiencies of vitamins C, B, and D have improved in recent years. Micronutrient deficiencies and protein and calorie deficiencies must be addressed for optimal growth and development to be attained.
Etiology
Inadequate food intake is the most common cause of malnutrition worldwide. In developing countries, inadequate food intake is secondary to insufficient or inappropriate food supplies or early cessation of breastfeeding. In some areas, cultural and religious food customs may play a role. Inadequate sanitation further endangers children by increasing the risk of infectious diseases that increase nutritional losses and alters metabolic demands.
In developed countries, inadequate food intake is a less common cause of malnutrition. Instead, diseases and, in particular, chronic illnesses play an important role in the etiology of malnutrition. Children with chronic illness are at risk for nutritional problems for several reasons, including the following:
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Children with chronic illnesses frequently have anorexia, which leads to inadequate food intake
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Increased inflammatory burden and increased metabolic demands can increase caloric need
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Any chronic illness that involves the liver or small bowel affects nutrition adversely by impairing digestive and absorptive functions
Chronic illnesses that commonly are associated with nutritional deficiencies include the following:
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Cystic fibrosis
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Chronic renal failure
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Childhood malignancies
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Congenital heart disease
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Neuromuscular diseases
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Chronic inflammatory bowel diseases
In addition, the following conditions place children at significant risk for the development of nutritional deficiencies:
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Prematurity
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Developmental delay
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In utero toxin exposure (ie, fetal alcohol exposure)
Children with multiple food allergies present a special nutritional challenge because of severe dietary restrictions. Patients with active allergic symptoms may have increased calorie and protein needs.
Guidelines from the American Academy of Pediatrics recommend that the evaluation of children with malnutrition should include assessment of their juice intake. Excessive juice consumption may be associated with malnutrition (overnutrition and undernutrition). [11]
Pathophysiology
Malnutrition affects virtually every organ system. Dietary protein is needed to provide amino acids for synthesis of body proteins and other compounds that have various functional roles. Energy is essential for all biochemical and physiologic functions in the body. Furthermore, micronutrients are essential in many metabolic functions in the body as components and cofactors in enzymatic processes. (See the images below.)
In addition to the impairment of physical growth and of cognitive and other physiologic functions, immune response changes occur early in the course of significant malnutrition in a child. These immune response changes correlate with poor outcomes and mimic the changes observed in children with acquired immune deficiency syndrome (AIDS). Loss of delayed hypersensitivity, fewer T lymphocytes, impaired lymphocyte response, impaired phagocytosis secondary to decreased complement and certain cytokines, and decreased secretory immunoglobulin A (IgA) are some changes that may occur. These immune changes predispose children to severe and chronic infections, most commonly, infectious diarrhea, which further compromises nutrition causing anorexia, decreased nutrient absorption, increased metabolic needs, and direct nutrient losses.
Early studies of malnourished children showed changes in the developing brain, including a slowed rate of growth of the brain, lower brain weight, thinner cerebral cortex, decreased number of neurons, insufficient myelinization, and changes in the dendritic spines. More recently, neuroimaging studies have found severe alterations in the dendritic spine apparatus of cortical neurons in infants with severe protein-calorie malnutrition. These changes are similar to those described in patients with intellectual disability of different causes. There have not been definite studies to show that these changes are causal rather than coincidental. [12]
Fat stores can decrease to as low as 5% of the total body weight and can be macroscopically undetectable. The remaining fat is usually stored in the liver, giving a paradoxical appearance of a fatty liver. Although this is often observed in kwashiorkor, it also occurs to a lesser extent in marasmus. Other pathologic changes include fatty degeneration of the heart, atrophy of the small bowel, and decreased intravascular volume leading to secondary hyperaldosteronism.
Epidemiology
United States statistics
According to the Global Nutrition Report, 3.4% of US children aged younger than 5 years are affected by chronic undernutrition, as indicated by low height for age (stunting). Additionally, 0.1% of children younger than 5 years are affected by acute undernutrition, as indicated by low weight for height (wasting). [13]
International statistics
The World Health Organization estimated that in 2024 about 150.2 million children aged younger than 5 years worldwide were affected by chronic undernutrition, as indicated by stunting. The overwhelming majority of these children live in developing countries. An additional 42.8 million children had acute undernutrition, as indicated by wasting. [1]
In 2022, the prevalence of stunting among children younger than 5 years in South Asia was 30.7%. The prevalence of wasting was 14.1%, which is the highest of any global subregion. In sub-Saharan Africa, the prevalence of stunting among children younger than 5 years was 32.5%, and the prevalence of wasting was 6.2%. Sub-Saharan Africa is the only global subregion where the number of children with stunting is increasing, reaching 62 million in 2022. [14]
Children are most vulnerable to the effects of malnutrition in infancy and early childhood. Premature infants have special nutritional needs that are not met with traditional feeding recommendations; they require fortified human milk or specially designed preterm formula until later in infancy.
Children are susceptible to malnutrition for differing reasons. No sexual predilection is observed, although in some parts of the world, cultural practices place girls at a disadvantage for protein-energy malnutrition. During adolescence, self-imposed dietary restrictions contribute to the incidence of nutritional deficiencies.
Paradoxically, a massive global epidemic of obesity, especially in countries in rapid economic transition, is simultaneously emerging in children and adolescents. The concurrent manifestation of both undernutrition and overweight/obesity has been termed the double burden of malnutrition (DBM). The greatest concentration of the DBM is found in sub-Saharan Africa, South Asia, and East Asia and the Pacific region. [15]
Prognosis
Children who have chronic malnutrition, especially those with intrauterine growth retardation and with onset at an early age, do not achieve their full growth potential or regain cognitive deficits. Although malnutrition is rare in the United States and other industrialized countries, nearly 50% of childhood mortality in developing countries is either directly or indirectly secondary to malnutrition.
Morbidity/mortality
The adverse effects of malnutrition include physical and developmental manifestations. Poor weight gain and slowing of linear growth occur. Impairment of immunologic functions in these children mimics those observed in children with AIDS, predisposing them to opportunistic and other typical childhood infections.
In developing countries, poor perinatal conditions account for 23% of deaths in children younger than 5 years. Malnourished women are at high risk of giving birth to low birth weight infants. Many low birth weight infants (15-20% of all births worldwide) [16] face severe short-term and long-term health consequences, such as growth failure in infancy and childhood, which increases risk of morbidity and early death. [6]
Children who are chronically malnourished exhibit behavioral changes, including irritability, apathy and decreased social responsiveness, anxiety, and attention deficits. In addition, infants and young children who have malnutrition frequently demonstrate developmental delay in achievement of motor skills and delayed mental development, and they may have permanent cognitive deficits.
The degree of delay and deficit depends on the severity and duration of nutritional compromise and the age at which malnutrition occurs. In general, nutritional insults at younger ages have worse outcomes. Dose-dependent relationships between impaired growth and poor school performance and decreased intellectual achievement have been shown. [17, 18]
A meta-analysis identified the following independent factors associated with mortality in children hospitalized for complicated severe acute malnutrition [19] :
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HIV infection
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Diarrhea
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Pneumonia
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Shock
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Lack of appetite
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Lower weight-for-height z score
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Hormonal adaptation to the stress of malnutrition: The evolution of marasmus.
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A classic example of a weight chart for a severely malnourished child.
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This infant presented with symptoms indicative of a dietary protein deficiency, including edema and ridging of the toenails. Image courtesy of the Centers for Disease Control and Prevention.
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This infant presented with symptoms indicative of Kwashiorkor, a dietary protein deficiency. Note the angular stomatitis indicative of an accompanying Vitamin B deficiency as well. Image courtesy of the Centers for Disease Control and Prevention.
