Zinc is present in all organs/ tissues (bone, liver, kidney, muscle and skin) and fluids. Digestion, absorption transport- zinc separated from amino acids and nucleic acids. Main site for Zn absorption jejunum, mechanism of absorption- passive diffusion, paracellular zinc absorption, carrier mediated process. Absorption is between 12% to 59% with higher absorption % age from nonvegetarian diet. It is found throughout the body, helps in the immunity system and metabolism function. It is also important to heal wounds and your sense of taste and smell. There is a varied variety in diet, usually the body gets enough zinc. Food sources of zinc include chicken, red meat and fortified breakfast cereals.
Zinc is the enterocyte which is used or stored within the enterocyte. Bound to protein is Cysteine rich Intestinal protein (CRIP) (transported across the enterocyte).
Zinc is transported in blood loosely bound to albumin which is stored in liver, kidney and bones. It is excreted through the GI tract (which is the major route) and even kidney, body surfaces.
It is associated with more than 300 enzymes. The enzymes which are dependent on enzymes are Carbonic anhydrase (in RBCs, kidney tubules) essential for respiration and rapid disposal of carbon dioxide and other enzymes.
Role as zinc fingers - (there are protein with finger like shape) there are zinc fingers which are DNA binding proteins (transcription factors) bind to promoter genes and regulate transcription, DNA binding zinc fingers (proteins) bind thyroid hormones, vit D, other steroid hormones and also with DNA to affect gene expression.
Zinc and growth, zinc plays a role in synthesis and metabolism of nucleic acid (DNA) and proteins, periods of rapid growth- zinc requirements is more, deficiency leads to poor growth, disturbance in lean tissue synthesis, retards growth by disrupting function of insulin like growth factor (IGF-1) which meditates cellular effects of growth hormones. Serum IGF-1 levels decrease in Zn deficiency.
Deficiency during pregnancy may cause poor fetal growth, fetal resorption, congenital malformation, IUGR and complications during parturition, increased morbidity and mortality in mother and neonates. Low Zn intake- low levels of IGF1.
Zinc is the integral part of copper - zinc superoxide dismutases and stabilizes cell membrane by protecting against oxidation; this is the antioxidant role played by it.
Absorption of lipid soluble vitamins as deficiency leads to impaired absorption of fat soluble vitamins and impairs mobilization of vitamin A from liver.
Zinc and brain development works such that the zinc deficiency leads to alterations in brain growth and development, in fetus deficiency may lead to primary neural tube defect. Alzhimer’s disease, Down’s syndrome, Epilepsy, Multiple sclerosis, Schizophrenia- changes in brain zinc concentrations have been observed.
Food sources for zinc are oysters, Shellfish, Liver, Whole grain cereals, Dry beans, Nuts and soy products.Bioavailability from plant sources affected by presence of phytic acid and fiber etc.
Zinc deficiency leads to higher risk in people who are alcoholics, elderly women, chronic illness, stress, trauma, surgery, malabsorption, lacto-vegetarians and pregnant women.
Signs and symptoms for zinc deficiency leads to growth retardation, skeletal abnormalities( defective collagen synthesis/ cross linking), poor wound healing, skin lesions (acrodermatitis), delayed sexual maturation in children, hair loss (alopecia), impaired taste, night blindness, impaired immuine function, impaired protein synthesis, impaired appetite (anorexia), behavioral disturbances.
Hair loss, skin lesions, diarrhea, wasting of body tissues. Eye sight, taste, smell, memory adversely affected.
Immunological defects lead to mild deficiency to decreased immunity, impaired IL2
Acrodermatitis enteropathica, is a rare genetic disorder affecting uptake of Zinc, Congenital abnormality causing zinc deficiency. Features similar to features of acquired Zinc Deficiency and appear in the first few months of life, without treatment it is fatal. No cure, but lifelong Zn supplementation (1 to 2 mg/kg/d) Acute toxicity (1 to 2g zinc sulfate)- produce metallic taste, nausea, vomiting, epigastric pain, abdominal cramps, bloody diarrea.
Chronic ingestion of therapeutic doses results in copper deficiency.
Assessment measurements of Zn in RBC, leukocytes, neutrophils, serum, plasma. Measurement of Metallothionein, urinary and hair zinc levels. Measurement of activity of inc dependent enzyme.
Oral zinc can cause indigestion, diarrhea, headache, nausea, vomiting etc. when oral zinc is taken long term and in high doses it can cause copper deficiency. People with low copper levels might experience neurological issues, such as numbness and weakness in the arms and legs.
This article is written and submitted to The E Today by Shrushti Mehta.
We thank her for her research and analysis and hope to see the awareness about health and nutrition being spread ahead to larger mass of our citizens.