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.
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
Upper safe level for daily
supplementation = 15mg
Recommended Daily Allowance = 15mg
Requirements are increased in
Pregnancy.
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).
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 (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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