Zinc: an essential micronutrient.

Zinc is an essential micronutrient for human metabolism that catalyzes more than 100 enzymes, facilitates protein folding, and helps regulate gene expression. Patients with malnutrition, alcoholism, inflammatory bowel disease, and malabsorption syndromes are at an increased risk of zinc deficiency. Symptoms of zinc deficiency are nonspecific, including growth retardation, diarrhea, alopecia, glossitis, nail dystrophy, decreased immunity, and hypogonadism in males. In developing countries, zinc supplementation may be effective for the prevention of upper respiratory infection and diarrhea, and as an adjunct treatment for diarrhea in malnourished children. Zinc in combination with antioxidants may be modestly effective in slowing the progression of intermediate and advanced age-related macular degeneration. Zinc is an effective treatment for Wilson disease. Current data do not support zinc supplementation as effective for upper respiratory infection, wound healing, or human immunodeficiency virus. Zinc is well tolerated at recommended dosages. Adverse effects of long-term high-dose zinc use include suppressed immunity, decreased high-density lipoprotein cholesterol levels, anemia, copper deficiency, and possible genitourinary complications.