Zinc
DESCRIPTION
A component of over eighty enzymes, zinc functions in many reactions in the human body.
FUNCTIONS
Cell Division:
Zinc is necessary for normal cell division and function.
Immune System:
Zinc is found in alpha-macroglobulin, an important protein in the body?s Immune System. It is also needed for functioning of the thymus gland.
Growth:
Zinc is necessary for growth in children and maturation of the sex organs at puberty. The mineral is also needed for the production of male sperm and female ova.
Heavy Metal Detoxification:
Zinc helps clear certain toxic metals from the body (e.g. cadmium and lead).
Other Properties:
Zinc is also essential for the maintenance of vision, taste and smell; for the release of insulin and for the absorption and metabolism of Vitamin A.
DEFICIENCY
The following may indicate that zinc is in short supply:
Frequent Infections
Delayed Wound healing
Reduced appetite
Decreased sense of taste or smell
Skin disorders
White marks on nails
REQUIREMENTS
Upper safe level for daily supplementation = 15mg
Recommended Daily Allowance = 15mg
Requirements are increased in Pregnancy.
SUPPLEMENTAL USES
A supplement of zinc may be helpful in the following situations:
Skin Conditions:
Zinc supplementation has been shown to be effective in some types of Skin conditions, such as Acne (1) and Eczema.
Prostate:
The prostate contains high amounts of zinc compared to other organs. In prostatitis (Inflammation of the prostate) and prostate cancer zinc levels are markedly decreased (2, 3). Zinc inhibits androgen metabolism in the prostate (2) and may be of benefit to older men.
Wound Healing:
Low zinc levels are linked with poor Wound healing. As a result, zinc supplementation may help to accelerate the healing process (4).
Alcoholism:
Zinc supplementation may help prevent Cirrhosis of the liver (5) due to Alcoholism.
Fertility:
Zinc is found in high quantities in the testes. Zinc deficiency results in depletion of testosterone and inhibits sperm formation. This mineral is also thought to extend the life span of ejaculated sperm. In females, zinc deficiency is linked with impaired hormone secretion, abnormal ovarian development, frequent abortion, prolonged gestation period, still births and low birth weight babies (6).
Brain Function:
Zinc supplementation may reverse some of the poor behaviour (and responsiveness) exhibited by low birth weight babies. Zinc appears to affect brain function by modulating neurotransmitter (GABA) production (7).
SAFETY
After acute ingestion of 2g or more of zinc, symptoms such as nausea, Vomiting and fever develop. Long-term intakes of around 75-300mg zinc are associated with features of Copper deficiency such as neutropenia (low levels of the neutrophil type of white blood cell) and Anaemia.
INTERACTIONS AND CONTRA-INDICATIONS
Copper:
High levels can induce a deficiency of Copper and so zinc supplements may contain copper to make up for this.
Iron:
Excess zinc intake may interact with Iron and has the potential to cause a deficiency of this mineral.
Antibiotics:
Zinc interferes with the absorption of the drug tetracycline and vice versa, and so these two should be taken a few hours apart.
Nausea:
Zinc supplements should not be taken on an empty stomach because they can occasionally cause nausea.
Other Drugs:
Cortisone drugs and the thiazide diuretics are known to increase the excretion of zinc, and penicillamine (a metal binding drug), is known to block zinc?s absorption.
FOOD SOURCES
Food (mg/100g)
Cheese. Cheddar 4.0
Beef, stewing steak 3.8
Lentils 3.1
Bread, wholemeal 1.8
Eggs 1.5
Chicken 1.1
Bread, white 0.6
Fish, white 0.4
Milk 0.4
Potatoes, old 0.3
REFERENCES
1. Dreno B, et al. Low doses of zinc gluconate for inflammatory Acne. Acta Derm Venereol, 69;6:541-3, 1989.
2. Dutkiewicz S. Zinc and Magnesium serum levels in patients with Benign Prostatic Hyperplasia (BPH) before and after prazosin therapy. Mater Med Pol, 27;1:15-17, 1995.
3.Zaichick Vye, Sviridova TV and Zaichick SV. Zinc in the human prostate gland: normal, hyperplastic and cancerous. Urol Nephrol, 29;5:565-574, 1997.
4. Pamela Mason "Handbook of Dietary Supplements", , Blackwell Science, 1995.
5. Rocchi E et al. Zinc and Magnesium in liver Cirrhosis. Eur J Clin Invest, 24;3:149-155, 1994.
6. Bedwal RS, Bahuguna A. Zinc, Copper and Selenium in reproduction. Experimentia, 50;7:626-640, 1994.
7. Ashworth A et al. Zinc supplementation, a mental development and behaviour in low birth weight term infants in North East Brazil. Eur J Clin Nutrition, 52;3:223-227, 1998.
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