16 Nutritional Deficiencies

Assessment of a pediatric patient’s nutritional status includes evaluation of the child’s current and past medical problems, dietary intake, growth parameters, physical examination, and often laboratory tests. Establishing normal growth and development, prevention, and early identification of nutritional deficiencies is the goal in assessing a patient’s nutritional status. When evaluating a patient for specific nutritional deficiencies, clinical findings as well as laboratory data may be helpful. Children with mild nutritional deficiencies often present with nonspecific signs and symptoms that are discussed in Chapter 17. However, when severe deficiencies are present, the presentation will be more pronounced, as described in this chapter. Serum albumin can be used to determine long-term nutritional status, and serum prealbumin provides assessment of the adequacy of short-term dietary intake (see section on malnutrition for further information). A complete blood count (CBC) with red blood cell (RBC) indices can be used to identify deficiencies of iron, folate, vitamin B₁₂, and anemia of chronic disease. Laboratory assessment of fat-soluble vitamins (A, E, and D) is more easily measured than are water-soluble vitamins.

Deficiencies

Iron

There has been a significant decrease in iron-deficiency anemia in the past 30 years as a direct result of universal screening guidelines as well as iron fortification of formulas and cereals. It is important for pediatricians to monitor their patients’ iron intake because primary prevention is necessary to prevent irreversible mental, motor, and behavioral effects.

The greatest risk factor for the development of iron-deficiency anemia is the early introduction of cow’s milk (before age 1 year) because of its low iron content and poor bioavailability. Nursing mothers should maintain an adequate source of their own dietary or supplemental iron. Breast milk has low iron content, but it is highly bioavailable. After 6 months of age, breastfed infants require iron-rich foods such as egg yolk, leafy green vegetables, proteins, or iron-fortified cereals. After the introduction of cow’s milk at age 1 year it is important to limit intake to no more than 16 to 24 oz/d to prevent iron deficiency.

All infants can be screened for iron-deficiency anemia between 9 and 12 months of age by assessing dietary iron intake and with laboratory data. Although a hemoglobin value determines anemia, a CBC with RBC indices helps to delineate iron-deficiency from other anemias. One may choose to use an empiric treatment of iron-fortified vitamins when mild iron-deficiency anemia is suspected. Determining serum iron levels and total iron binding capacity will support the use of elemental iron treatment.

Iodine

Iodine is an essential component of thyroid hormone that is crucial for growth and development. Iodine is absorbed through the intestines in the form of iodide and is then taken up by the thyroid gland for incorporation into thyroxin (T4) and triiodothyronine (T3). Before the iodization of salt in 1920, iodine deficiency was endemic in the United States, and it is still the most common preventable cause of mental retardation worldwide. A deficiency of iodine is the most common cause of goiter, an enlargement of the thyroid gland, which, if large enough, may produce symptoms such as hoarseness or dysphagia as a result of local compression. Iodine deficiency and subsequent thyroid hormone deficiency can manifest with symptoms of hypothyroidism, such as weight gain, fatigue, and constipation. The most severe consequence of iodine deficiency is congenital hypothyroidism (mental retardation, deaf-mutism, gait abnormalities, and short stature), which can be prevented by adequate iodine intake both during pregnancy and early infancy (Figure 16-1).

Figure 16-1 Congenital hypothyroidism.

Zinc

Zinc, an essential cofactor necessary for growth and development, is often available in adequate levels for full-term infants fed formula or who are breastfed by mothers who themselves have adequate zinc levels. Zinc deficiency is usually caused by intestinal loss from diarrhea or malabsorptive states but can also be caused by renal disease, malignancy, and skin conditions such as acrodermatitis enteropathica. The clinical diagnosis is supported by findings that include growth failure, dermatitis (an erythematous, scaly rash found on the face and perineal region), and impaired wound healing. Laboratory measurements of zinc are often unreliable because of fluctuations seen in various disease states.

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