ABSTRACT
Nearly 100 years ago, zinc was shown to be essential for microorganisms. In 1934 two groups of workers showed convincingly that zinc was required for the growth and well-being of rats. A disease called parakeratosis of swine was related to zinc deficiency in 1955, and it was shown to be essential for the birds in 1958. Clinical manifestations in zinc-deficient animals include growth retardation, testicular atrophy, skin changes, and poor appetite. The anemia was due to iron deficiency even though no source of blood loss could be documented. Nutritional deficiency of zinc in humans is fairly prevalent throughout the world. Besides Iran and Egypt, it has now been reported from Turkey, Portugal, Morocco, Yugoslavia, and other developing countries. Zinc deficiency should be prevalent in other countries where primarily cereal proteins are consumed by the population. Plasma zinc levels have been measured in infants and young children suffering from kwashiorkor in Cairo, Pretoria, Capetown, and Hyderabad.
