ROLE OF ZINC IN CHILDREN
Zinc is a trace element that is essential for normal growth and development of infants and children. Zinc is a constituent of more than 100 metalloenzymes and is essential for growth, protein synthesis, epithelial repair and synthesis of RNA and DNA. Total body zinc is 2.3 gm with primarily intracellular accumulation. High levels are found in choroids of the eyes, prostrate, kidneys, liver, muscles and bones.
Sources of Zinc:- Meat, eggs, nuts, cheese, oysters and grains are good sources of zinc. Cereal diets rich in phytates decrease the absorption of zinc by binding to zinc. Thus zinc deficiency is more common in developing countries who have this kind of diet. Vegetarians are also prone to zinc deficiency.
Zinc Absorption:- The mechanism of absorption of zinc is not very clear at the moment. Zinc absorption and excretion takes place in the intestine and inadequate dietary intake, malabsorption, cirrhosis, celiac disease, Crohn's disease, chronic diarrhea can all lead to zinc deficiency. On intake of zinc, absorbed zinc is taken up by the liver and then distributed to other tissues. Serum zinc levels rise after a meal and then fall in a dose responsive pattern. Zinc losses can occur in the urine from use of diuretic drugs caffeine, ACE inhibitors, chelating agents, burns, trauma and hemolytic anemia. Sodium valproate, Ethambutol also decrease the serum zinc levels. Genetic mutations can lead to zinc depletion by increasing zinc loss in the GI tract or through sweat. Cellular zinc may be depleted by stress or illness. Too much supplementary iron can interfere with zinc absorption.
Recommended Daily Allowance of Zinc
Pregnancy and lactation:- Nursing and pregnancy increases zinc needs due to increased requirements as well as increased prolactin levels which requires zinc for its function.
Clinical manifestation of zinc deficiency:-
Because zinc is required for many functions in the body, deficiency of zinc can lead to a wide variety of symptoms and clinical manifestations. Zinc deficiency is predominantly seen in patients with malabsorption, poor dietary intake, pregnancy, lactation, preterms children with pica and elderly individuals.
Mild zinc deficiency:- Mild zinc deficiency can lead to
Moderate and severe zinc deficiency
Zinc deficiency in the pregnant woman can lead to intrauterine growth retardation.
Acrodermatitis enteropathica:- It is an autosomal recessive condition and is characterized by failure of zinc absorption, growth retardation, hypogonadism, eczematoid skin lesions, diarrhea and poor appetite and alopecia. Daily zinc supplementation (20-40 mg/day) results in recovery. Untreated it progresses to severe malnutrition, recurrent intercurrent infections and eventually death.
Diagnosis of zinc deficiency:-
Diagnosis of hypozincemia can be established by estimating plasma zinc level. Normal serum zinc levels in children are 66 to 194 µg/10 ml.
Treatment of zinc deficiency
Zinc supplements in doses of 35-40 mg daily can be used for treatment of zinc deficiency.
Other role of zinc supplements
Currently zinc is recommended as an additional therapy in PEM and chronic diarrhea.
It is also used in treatment of Wilson's disease. Wilson's disease is an autosomal recessive disorder characterized by failure of biliary excretion of excess copper. This excess copper causes liver or brain damage. Zinc blocks the absorption of copper and increases copper excretion in the stool.
Zinc has been found to be useful as an adjunct in patients with respiratory infections, malaria, but further evidence is requied for qualifying its use in these conditions.
Zinc toxicity:- Excessive intake of zinc (100 mg to 300 mg/day) can lead to toxicity. Zinc supplement in amounts of 2 gm/day can lead to acute toxicity leading to nausea, vomiting, abdominal pain, diarrhea, convulsions. Chronic toxicity can lead to lethargy, anemia, neutropenia and CNS disturbances predominantly due to lowering of copper levels.
Last updated: 1-08-2006 Vol 3 Issue 8 Art # 27
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