Zinc in nutrition by nikhil

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Zinc in nutrition by nikhil

  1. 1.  1509, recognized as element  Essentiality demonstrated  Plants: 1869  Animals: 1934  Deficiency  Considered unlikely until 1955  conditioned human deficiency demonstrated in 1956  1961, hypogonadal dwarfism suggested to be zinc deficiency
  2. 2.  Relatively abundant mineral  Good sources: shellfish, beef and other red meats  Slightly less good: Whole-grains  most in bran and germ portions  80% lost to milling  phytates, hexa & penta phosphates depress absorption  P/Zn ratios of 10 or more  Relatively good sources: nuts and legumes  Eggs, milk, poultry & fish diets lower than pork, beef, lamb diets  High meat diets enhance absorption  280g or 10 oz fits right into food pyramid guide  cys & met form stable chelate complexes
  3. 3.  Zinc absorption is greater from a diet high in animal protein than a diet rich in plant proteins . Phytates, which are found in whole grain breads, cereals, legumes and other products, can decrease zinc absorption .
  4. 4.  Whole body: 1.5g (female)-2.5g (male)  Skeletal Muscle 57%  Bone 29%  Skin 6%  Liver 5%  Brain 1.5%  Kidneys 0.7%  Heart 0.4%  Hair ~0.1%  Blood Plasma ~0.1
  5. 5. Foods contain element zinc, much of it bound to protein or DNA.  Oysters (> 70 mg per serving).  Meats (2-3 mg/100g).  Shellfish (2.7 mg/100g)  Other good food sources include:  beans, nuts, certain seafood, whole grains, fortified breakfast cereals, and dairy products .
  6. 6.  Required for growth in children and infants.
  7. 7.  GIT modulates the quantity of exogenous dietary zinc absorbed and the quantity of endogenous zinc excreted  More than 70% of a small zinc dose (less than 3 mg) is absorbed from the small intestine.  Maximum absorption occurs in duodenum  There is sustained release from enterocytes into portal circulation for ~ 9h
  8. 8.  Zinc absorption mainly achieved by 2 families of zinc transporters; 1. ZIP Family 2. ZnT Family
  9. 9.  Routes: intestine, kidneys, integument, and semen  After a meal, maximum zinc secretion occurs through pancreatobiliary secretions  Maximum reabsorption occurs from mid-jejunum and ileum  Total amount excreted = Amount secreted – Amount reabsorbed  Excretion of endogenous zinc by the intestine depends on the ‘zinc status’ of the body.
  10. 10.  Causes;  Malnutrition  Alcoholism  Malabsorption  Burns  Chronic renal disease  Acrodermatitis enteropathica
  11. 11.  Signs  Growth retardation  Delayed sexual maturation & impotence  Impaired testicular development  Hypogonadism & hypospermia  Alopecia  Acroorifical skin lesions  Other, glossitis, alopecia & nail dystrophy  Immune deficiencies  Behavioral changes
  12. 12.  Night blindness  Impaired taste (hypoguesia)  Delayed healing of wounds, burns, decubitus ulcers  Impaired appetite & food intake  Eye lesions including photophobia & lack of dark adaptation
  13. 13. 1. Severe  dermatitis, alopecia, diarrhea, emotional disorder, weight loss, infections, hypogonadism in males 2. Moderate  growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities and abnormal dark adaptation 3. Mild  oligospermia, slight weight loss and hyperammonaemia
  14. 14.  Zn deficient rats failed to conceive  Abnormalities of blastocyst development  Offspring had high incidence of abnormalities  Deformities of brain, skull, limbs, eyes, heart, lungs  Low Zn intake during the third trimester may not have such profound effects  Main stages of differentiation are already complete  Can result in low birth weight, and prolonged and difficult parturition
  15. 15.  Excess accumulation within cells may disrupt functions of biological molecules  Protein, enzymes, DNA  Leads to toxic consequences  Anemia  Impaired copper availability  Acute excessive intakes  Local irritant to tissues and membranes  GI distress, nausea, vomiting, abdominal cramps, diarrhea  Relatively non-toxic  Sources of exposure – drinking water, feed, polluted air
  16. 16.  Genetic disorder of zinc absorption.  Presents during infancy.  Characterized mainly by a triad consisting of 1. Acral dermatitis 2. Alopecia 3. diarrhea
  17. 17.  In infants bottle fed with bovine milk, days to week, breast fed infants soon after feeding  In older children its acquired zinc deficiency.
  18. 18.  Acrodermatitis enteropathica; autosomal recessive trait resulting in failure to absorb zinc.  Acquired zinc deficiency; secondary to reduced dietary intake , malabsorption, increased urinary loss, etc.
  19. 19.  Skin mucous membrane and hair are involved.  Lesions are pink and later become brightly erythematous.  Impaired wound healing.  Irritable with depressed mood  Growth failure
  20. 20.  Loss of weight  Sensitivity to light  Diarrhea  Conjuctivitis  Red glossy tongue and mouth ulcers
  21. 21.  Complete blood count  Serum/ plasma zinc levels  Urine; zinc excretion is reduced  Dermatopathology; intraepidermal clefts and blisters
  22. 22.  1mg/kg body weight of oral zinc supplementation per day of life.  Zinc gluconate better tolerated than sulfate.  Dietary or iv supplementation with zinc salts with two or three times , the RDA restores normal zinc status in days or week.
  23. 23.  All children above 6months should receive a uniform dose of 20mg elemental zinc as soon as diarrhoea starts and continue for 14 days.  2 to 6mnths- 10mg/day for 14 days.

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