Zinc (Zn) is contained mainly in bones, teeth, hair, skin, liver, muscle, leukocytes, and testes. Zinc is a component of several hundred enzymes, including many nicotinamide adenine dinucleotide (NADH) dehydrogenases, RNA and DNA polymerases, and DNA transcription factors as well as alkaline phosphatase, superoxide dismutase, and carbonic anhydrase.
A diet high in fiber and phytate (eg, in whole-grain bread) reduces zinc absorption.
(See also Overview of Mineral Deficiency and Toxicity.)
Dietary deficiency is unlikely in healthy persons. Secondary zinc deficiency can develop in the following:
Maternal zinc deficiency may cause fetal malformations and low birth weight.
Zinc deficiency in children causes impaired growth, impaired taste (hypogeusia), delayed sexual maturation, and hypogonadism. In children or adults, manifestations also include alopecia, impaired immunity, anorexia, dermatitis, night blindness, anemia, lethargy, and impaired wound healing.
Zinc deficiency should be suspected in undernourished patients with typical symptoms or signs. However, because many of the symptoms and signs are nonspecific, clinical diagnosis of mild zinc deficiency is difficult. Laboratory diagnosis is also difficult. Low albumin levels, common in zinc deficiency, make serum zinc levels difficult to interpret; diagnosis usually requires the combination of low levels of zinc in serum and increased urinary zinc excretion. If available, isotope studies can measure zinc status more accurately.
Treatment of zinc deficiency consists of elemental zinc 15 to 120 mg orally once/day until symptoms and signs resolve.
Acrodermatitis enteropathica (a rare, once fatal autosomal recessive disorder) causes malabsorption of zinc. Psoriasiform dermatitis develops around the eyes, nose, and mouth; on the buttocks and perineum; and in an acral distribution. The disorder also causes hair loss, paronychia, impaired immunity, recurrent infection, impaired growth, and diarrhea. Symptoms and signs usually develop after infants are weaned from breast milk. In such cases, doctors suspect acrodermatitis enteropathica. If this diagnosis is correct, zinc sulfate 30 to 150 mg/day orally usually results in complete remission.