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home - Nutrition - Minerals - Zinc Written by Dr Sebastian Zeki

Zinc

Evaluation of zinc statusPlasma concentration can be falsely depressed in inflammation- erythrocyre [zinc] is more reliable.Superoxide dismutase or erythrocyte alkaline phosphatase activities are indirect markers. 30% absorbed Forms complexes with ligands amino acids, phosphates, organic acids, and histidines. Metallothionein (also absorbs copper) but prefers zinc Pancreatic disease or insufficiency.Phytic acidCompetes with iron and copper Albumin Zinc Meat and chicken nuts and lentils.RDA: Children 3mg/d.Women 8mg/d.Men 11mg/d. Peripheral tissues (bone and muscle pools) Liver Stored as metallothio-neinTotal body pool 2g Dietary Deficiency Clinical Presentation:Impaired growth velocity- occurs with mild dietary zinc deficiency .Growth retardation with severe depletion of zinc.Delayed sexual maturation.Impotence.Hypogonadism.Oligospermia.Alopecia.Change in hair colour.Easy pluckability of hair.Dysgeusia (impaired taste).Immune dysfunction.Night blindness.Impaired wound healing.Various skin lesions (primarily in the extremities or around body orifices and are characterized by erythematous, vesiculobullous, and pustular lesions).Skin manifestations (acro-orificial dermatitis, erythematous, vesiculobullous, and pustular lesions).Decubitus ulcers. ToxicityToxicity is well tolerated.It gives a non specific GI upset.It can cause copper deficiency.Treatment is supportive or CaNa2EDTA if severe. Deficiency- Acrodermatitis enteropathica AR Mutations in the SLC39A4 gene on chromosome 8q24.3 Encodes a zinc transport protein Severe zinc deficiencyResolves with oral zinc therapy AlopeciaPerioral and perianal hyperpigmented dermatitisDiarrhoeaPoor growthImmune dysfunctionIrritability and lethargy At risk populations:Developing world (poor diet + large phytate intake) Diabetics (increased urinary zinc excretion which may explain immune compromise)Chronic TPN without zincChronic zinc losing conditions eg diarrhoeaAlcoholic cirrhoticPregnancy (spplementation reduces prematuraity and increases foetal growth) Biological role Zinc: Jejunum Cell division as well as apoptosis. Enzymes (due to tight binding with histidine and cysteine:Angiotensin converting enzymeAlkaline phosphataseCarbonic anhydrase DNA and RNA polymerasesCopper-zinc superoxide dismutaseMetallothioneinZinc proteins involved in gene transcription (such as the zinc finger proteins) Written by Dr Sebastian Zeki

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