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    Zinc deficiency

    Zinc is one of the vital micronutrient required for normal metabolic functions. It is a cofactor in various enzymes and is an important nutrient involved in protein and nucleic acid synthesis. Zinc deficiency leads to growth retardation, malabsorption, diarrhea, impaired immunity, and skin changes,.

    Zinc is absorbed in the small intestine. It is chiefly distributed in muscles, liver, reproductive organs, bones and brain. Average human body contains about 2 g of zinc.

    zinc supplemets
    Zinc supplements to treat deficiency.

    Functions of zinc

    • Zinc is an integral component of many enzymes resposible for metabolic functions in the body. It is involved in the synthesis and stabilization of proteins, DNA, and RNA's.

    • Zinc is necessary for the binding of steroidal hormones receptors and several other transcription factors to DNA and thereby plays an important role in the regulation of transcription.

    • Zinc is absolutely required for normal spermatogenesis, fetal growth, and embryonic development.

    • Zinc is essential mineral required for the healthy growth of hair, nails, and skin.

    • Zinc has been found to increase cell-mediated immunity.

    • Zinc helps in vitamin-A metabolism and normal blood levels of zinc is essential for restoration of night vision.

    Recommended dietary allowances of zinc-

    Category Age Group RDA
    Infants 0-6 months 5 mg
    6-12 months 5 mg
    Children 1-10 years 10 mg
    Males (younger) 11-18 years 15 mg
    Males (older) 19 and above 15 mg
    Females 11-50 years 12 mg
    51 and above 12 mg
    Pregnant woman 15 mg
    Lactating Mother 19 mg

    Causes of low zinc levels

    Normal serum level is 60-150 μg%. In malnourished children values can be as low as 20-25 μg%. Its absorption is inhibited by dietary phytates, fiber, oxalate, iron, copper as well as drugs like penicillamine, sodium valproate, and ethambutol.

    Causes of poor intake and low absorption (bio-availability) of zinc:

    1. Zinc in vegetables, fruits and grains is less available for absorption.

    2. Mild zinc deficiency has been described in many diseases like diabetes, AIDS, cirrhosis, alcoholism, IBD, and sickle cell disease.

    3. Deficiency occurs in Protein energy malnutrition (PEM), Total parenteral nutrition (TPN), hepatitis, and nephritic syndrome.

    4. Deficiency produces thymic atrophy and serum thymulin levels can be used to detect early zinc deficiency.



    Signs and symptoms of zinc deficiency

    Symptoms include-

    • Mild chronic zinc deficiency can cause stunted growth in children

    • Hair fall

    • Dry, flaky skin

    • Decreased taste sensation

    • Delayed wound healing

    • Thymus gland atrophy and Impaired immune function

    • Night blindness (due to impaiered converion of retinol to retinoldehyde).

    Severe chronic zinc deficiency has been described as a cause of hypogonadism and stunted growth (dwarfism). In children premature graying of hair (hyopigmentation) also occurs.

    Acrodermatitis enteropathica responds to zinc therapy. It produces crusting dermatitis in around the mouth (periorificial regions), bullae in palms and soles and diarrhea.


    Food sources of zinc

    The sources are lamb, liver, beef, oyster, pulses, nuts, cereals, and dry fruits. Zinc supplementation has been shown to result in better catch up in height in those with LBW and malnutrition.

    Refer the table for food sources of zinc.

    See the table below for in depth analysis:

    Zinc value per 100 g of food.

    (Source: USDA National Nutrient database)
    Food source Nutrient Value Percentage of RDA
    Animal sources
    Beef, lean meat, cooked 8.01 mg 73%
    Bison, game meat, cooked 8.64 g 78%
    Cheese, feta 2.88 mg 26%
    Chicken, cooked 2.26 mg 20.5%
    Egg, whole, fried 1.39 mg 13%
    Lamb, lean meat 2.05 mg 19%
    Milk 0.22 mg 2%
    Seafood/Mollusk
    Fish, Herring 0.99 mg 9%
    Spiny lobster, cooked 7.27 mg 66%
    Octopus, common, raw 1.68 mg 15%
    Oyester, Pacific 16.62 mg 151%
    Plant sources
    Fruits
    Apricot, dehydrated 1 mg 9%
    Currants, zante, dried 0.66 mg 6%
    Vegetables
    Amaranth leaves, cooked 0.88 mg 8%
    Bamboo shoots, raw 1.10 mg 10%
    Garlic, raw 1.16 mg 10%
    Green peas, raw 1.24 mg 11%
    Mushrooms, chanterelle, raw 0.71 mg 6%
    Soybeens, green, raw 0.99 μg 9%
    Nuts and seeds
    Almonds, dry roasted 3.13 mg 28%
    Hazelnuts 2.45 mg 22%
    Pumpkin seeds, dried 7.64 mg 69%
    Sunflower seeds, toasted 5.21 mg 47%

    Zinc Supplements

    Zinc formulations for infants to adults available as tablets, syrup and lozenges to treat zinc deficiany, following physician consultation. Zinc supplements generally advocated to reduce cold (flu) symptoms, respiratory infections and diarroea incidences in developing countries.

    Health risks of excessive zinc intake

    Acute zinc toxicity after oral ingestion causes nausea and vomiting, fever, abdominal pain, and respiratory distress. Excess can produce iron and copper deficiency. Zinc is also useful in the treatment of wilson's disease (excess of copper levels in the body) since it inhibits the body's absorption of copper. Excess can also produce GI upset. (Medical disclaimer).



    <<-Read on Essential fatty acids.

    <<-Read Iron deficiency anemia.

    <<-Back to Nutrition articles from Zinc deficiency.


    Further reading and References:

    1. National Institute of Health-Zinc Dietary Supplement Fact Sheet.

    2. Micronutrient Information Center.

    3. USDA-National Agricultural Library.

    4. USDA Food Composition Dtabases.



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