Excerpt from Malnutrition

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Background

The World Health Organization defines malnutrition as "the cellular imbalance between supply of nutrients and energy and the body's demand for them to ensure growth, maintenance, and specific functions." Malnutrition is globally the most important risk factor for illness and death, contributing to more than half of deaths in children worldwide. Protein-energy malnutrition (PEM), first described in the 1920s, is observed most frequently in developing countries but has been described with increasing frequency in hospitalized and chronically ill children in the United States.

Kwashiorkor and marasmus are 2 forms of PEM that have been described. The distinction between the 2 forms of PEM is based on the presence (kwashiorkor) or absence (marasmus) of edema. 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 exist, some studies suggest that marasmus represents an adaptation to starvation whereas kwashiorkor represents a dysadaptation to starvation.

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 childbearing women throughout the world include deficiencies of iron, iodine, zinc, and vitamin A and are estimated to affect as many as two 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, while deficiencies of vitamin 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 in these individuals.

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 a variety of 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.

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 mental retardation of different causes. There have not been definite studies to show that these changes are causal rather than coincidental.

Other pathologic changes include fatty degeneration of the liver and heart, atrophy of the small bowel, and decreased intravascular volume leading to secondary hyperaldosteronism.

Frequency

United States

Fewer than 1% of all children in the United States have chronic malnutrition.

Incidence of malnutrition is less than 10%, even in the highest risk group (children in shelters for the homeless).

Some studies indicate that poor growth secondary to inadequate nutrition occurs in as many as 10% of children in rural areas.

Studies of hospitalized children suggest that as many as one fourth of patients had some form of acute PEM and 27% had chronic PEM.

International

The World Health Organization estimates that by the year 2015, the prevalence of malnutrition will have decreased to 17.6% globally, with 113.4 million children younger than 5 years affected as measured by low weight for age. The overwhelming majority of these children, 112.8 million, will live in developing countries with 70% of these children in Asia, particularly the southcentral region, and 26% in Africa. An additional 165 million (29.0%) children will have stunted length/height secondary to poor nutrition.

Currently, more than half of young children in South Asia have PEM, which is 6.5 times the prevalence in the western hemisphere.

In sub-Saharan Africa, 30% of children have PEM.

Despite marked improvements globally in the prevalence of malnutrition, rates of undernutrition and stunting have continued to rise in Africa, where rates of undernutrition and stunting have risen from 24% to 26.8% and 47.3% to 48.%, respectively since 1990, with the worst increases occurring in the eastern region of Africa.

Mortality/Morbidity

Malnutrition is directly responsible for 300,000 deaths per year in children younger than 5 years in developing countries and contributes indirectly to over half the deaths in childhood worldwide.

• 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.
• 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 or 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 will have worse outcomes.
• Although death from malnutrition in the United States is rare, in developing countries, more than 50% of the 10 million deaths each year are either directly or indirectly secondary to malnutrition in children younger than 5 years.

Age

• 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. During adolescence, self-imposed dietary restrictions contribute to the incidence of nutritional deficiencies.

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