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 T.
J. Clark Liquid Zinc:
Zinc (Zn) is an essential trace mineral. The human
body has between 1.5?2.5 g Zn, making it nearly as
abundant as iron. It is highly concentrated in
specialized areas of the brain, pancreas and adrenal
gland, but is present in all cells, particularly in the
nucleus. Zinc has structural, catalytic (enzymatic) and
regulatory roles. About 1% of the human genome
codes for zinc finger proteins, where zinc provides a
structural role for regulatory functions. Over 60
enzymes require zinc for activity, including the RNA
polymerases. Zinc is actively taken up by synaptic
vesicles, supporting a role in neuronal activity and memory. Zinc
metabolism is altered during disease and physical stress through
hormones, cytokines and toxins, presumably as part of a host defense
response.
IMPORTANCE: Is an antioxidant nutrient; necessary for protein
synthesis; wound healing; vital for the development of the reproductive
organs, prostate functions and male hormone activity; it governs the
contractility of muscles; important for blood stability; maintains the
body's alkaline balance; helps in normal tissue function; aids in the
digestion and metabolism of phosphorus.
Deficiencies: An early sign of zinc deficiency in animals is decreased
food intake. It is a type II deficiency since a reduction in growth occurs
without an apparent reduction in tissue zinc. Reduced immune function,
involving B cell and T cell depletion and/or reduced activity, and skin
lesions associated with secondary infections are common findings.
Chronic zinc deficiency in humans results in reduced growth (dwarfism)
and sexual development which are reversible by raising zinc intake.
Signs of zinc deficiency may reflect its involvement in cell proliferation
and differentiation. Growth, behavioral abnormalities and cognition may
respond to zinc supplementation in some populations. Many clinical
findings that relate to depressed growth or immunity may have marginal
zinc deficiency as a secondary cause. May result in delayed sexual
maturity, prolonged healing wounds, white spots on finger nails, retarded
growth, stretch marks, fatigue, decreased alertness, susceptibility to
infections.
Clinical uses: Zinc is not widely used as a therapeutic agent except as
an ingredient of topical medication. Oral zinc may be used to treat
idiopathic skin lesions, some inflammatory conditions and depressed
immunity. Zinc is usually indicated in rehabilitation therapy from
malnutrition and/or malabsorption in children and adults, used in feeding
programs for premature infants and neonates and is also a component of
TPN solutions. Supplemental zinc reduces acute diarrhea and depressed
immunity.
Diet recommendations: The Recommended Dietary Allowances
(RDAs) are: infants, 5 mg/day; children <10 years, 10 mg/day; males
>10 years, 15 mg/day; females >10 years, 12 mg/day; pregnancy, 15
mg/day; and lactation, 0-6 mo., 19 mg/day; 7-12 mo., 16 mg/day.
Food sources: Zinc is highly abundant in red and white meat and
shellfish. Foods of plant origin except the embryo portion of grains, e.g.,
wheat germ, are low in zinc. Phytic acid in plants like soybeans binds
zinc, forming an insoluble complex that lowers bioavailability. Other
inhibitors of absorption are fiber, polyphenols and a high intake of
calcium. Zinc from human milk is more absorbable than that from infant
formulas or cow's milk.
Toxicity: Acute zinc toxicity is characterized by gastric distress,
dizziness and nausea. Symptoms of chronic toxicity include gastric
problems, decreased serum ceruloplasmin activity and hypocupremia,
decreased lymphocyte stimulation to PHA and reduced HDL
cholesterol. An emetic effect occurs at >150 mg Zn/day. Consumption
of zinc supplements produces measurable cellular effects but the long
term benefit/risk of zinc supplementation has yet to be determined.
Recent research: Experiments with transgenic and knock out mice are
defining the role for zinc metalloproteins in metabolism, development and
cytoprotection. Zinc as a component of an antioxidant system is being
evaluated. Zinc as a factor in Ab amyloid protein aggregation leading to
plaque formation found in Alzheimer's patients is under investigation.
Supplemental zinc has been proven to be of benefit in treatment of acute
diarrhea in infants and children. Fluorescent zinc indicators are in use to
define zinc functions at the cellular level.
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