Malnutrition refers to any condition caused by excess or deficient food energy, protein, or nutrient intake, or by an imbalance of nutrients. Nutrient or energy deficiencies are classified as forms of undernutrition; nutrient or energy excesses are forms of overnutrition. Malnutrition can take two forms: primary, due to a lack, excess, or imbalance of a nutrient or nutrients in the diet; and secondary, which occurs as a result of a disease or illness that affects dietary intake, nutrient needs, or metabolism. Historically, the most common nutrient-related problems among U.S. children are obesity, iron-deficiency anemia, and dental cavities. Protein-energy malnutrition (PEM), a problem in developing countries, is not common in the United States but can occur secondary to trauma, disease, psychological problems, or medical treatment. PEM occurs in two forms: marasmus, in which the deficiency is primarily in energy-providing foods, and kwashiorkor, characterized by inadequate protein in-take.
Inadequate maternal nutrition can affect fetal development. Although the body reserves of the mother are used to meet fetal growth needs, they cannot always insulate the fetus from dietary deficiencies. Inadequate nutrition can lead to a decrease in actual cell number and in cell size or growth. Cell number increases early in pregnancy; in the third trimester, size or growth of cells increases rapidly, along with number, and nutrient requirements are high. This active process continues after birth until one to two years of age. Restrictions that lead to decreased cell size can be reversed, but when the increase in cell number stops, it may be permanent.
See also: MARASMUS; MATURATION; MOTOR DEVELOPMENT; NUTRITION
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Nicole B. Knee