ZINC - ESSENTIAL FOR HEALTH AND THE ENVIRONMENT
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Zinc is essential to life. It is a natural element found in all plants
and animals and plays a crucial part in the health of our skin, teeth,
bones, hair, nails, muscles, nerves and brain function. Zinc and its
chemistry is found in over 200 enzymes and hormones in man.
Zinc deficiency is a recognised health problem. The Recommended Daily
Allowance (RDA) of zinc is l5mg for a male adult, a figure that is
easily met by a balanced diet containing meat and vegetables.
However, certain people require more zinc than others, pregnant and
lactating women for example, may need as much as l9mg a day. The
average elderly person's intake is only about 9mg a day due to the fact
that food consumption, especially of proteins, is often reduced and so
they may need to take a zinc supplement.
ZINC IN THE DIET
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- The
best sources of zinc are lean red meats, liver and certain seafoods
(especially oysters). Significant amounts are also found in nuts,
cereals, rice and dairy products.
- Food
processing techniques, such as stripping and bleaching grains to remove
their husks, reduces zinc bio-availability as well as other nutrients
and freezing or canning fruits and vegetables has a similar effect.
Cooking can also deplete zinc content.
- The
body absorbs zinc more readily from different sources, meat being a
particular good source in this respect. Phytate, found in grains and
other fibre-rich foods, binds with zinc and therefore reduces
absorption as can alcohol.
ROLE IN THE HUMAN BODY GROWTH
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- Zinc is essential for growth. It is used to control the enzymes that operate and renew the cells in our bodies.
- The formation of DNA, the basis of all life on our planet, would not be possible without zinc.
PREGNANCY AND INFERTILITY
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- Because of zinc's role in generating cells, it is essential for the developing foetus where cells are rapidly dividing.
- Adequate
zinc in the pregnant mother's diet also reduces the risk of premature
birth and other complications and has been shown to improve neonatal
survival.
- There is believed to be a link between zinc deficiency during pregnancy and learning difficulties.
- Research has been undertaken into the possibility of treating male
infertility with zinc therapy to increase sperm count and motility.
IMMUNE SYSTEM
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- Zinc
plays an important role in regulating the production of cells in the
body's immune system, which protects against infection and disease.
- As
we get older immunity often decreases. It has been shown that providing
adequate zinc and a balanced diet helps decrease the rate of infectious
diseases in older people.
BRAIN FUNCTIONS
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- Zinc interacts with other chemicals to send messages to the sensory brain centre, enhancing memory and thinking skills.
- In
the weeks following a head injury patients tend to have lower zinc
levels which, when boosted by zinc supplements, are thought to give
improved cognitive function.
- Zinc activates areas of the brain that receive and process information from taste and smell sensors.
- Insufficient zinc has been linked to anorexia, which responds well to zinc replacement treatment.
- Zinc
deficiency is often found in mood disorder patients. Zinc sulphate,
taken as a supplement, appears effective in reducing fatigue, mood
swings and changes in appetite
SKIN HEALING AND PROTECTION
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Zinc and zinc compounds are of major importance in skin care. Some of its vital uses are:
- To soothe nappy rash and itching thanks to its astringent and drying properties.
- As a sun-block to protect the skin from the sun's harmful rays.
- As an effective treatment for acne.
- In the relief of cold sore symptoms.
- To
aid the healing of wounds, like surgical incisions, burns and other
skin irritations. Many adhesive plasters contain zinc oxide for this
reason.
- As an anti-inflammatory to relieve the discomfort from sunburn, blisters and gum disease.
- As an insect repellent.
- Helping to protect body tissue from damage by stimulating the transport of Vitamin A from the liver to the skin,
- As bactericides in high quality cosmetics and toiletries.
- To help heal leg ulcers through addition to the diet.
EYESIGHT
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Zinc is found in high concentrations in the retina of the eye. Evidence
exists linking zinc deficiency with the deteriorating vision that comes
with ageing.
THE COMMON COLD
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- Zinc
gluconate lozenges, taken at the first sign of a common cold, reduce
duration and symptom severity by 42% according to a 1992 study. Zinc,
an antiviral agent and astringent, is released into the saliva,
relieving cough, nasal drainage and congestion.
- Besides shortening the duration of cold symptoms, zinc also soothes a rough, sore throat on contact.
GENETIC EXPRESSION
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- Groundbreaking research in zinc's role in genetic transcription and replication is being conducted.
- The
discovery of zinc "fingers", which activate hundreds of genes, promises
understanding of how growth promoters - like steroids - work and may
help treat tumours and viral diseases.
- Research into zinc "finger" proteins has already explained some genetic defects.
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EATING DISORDERS
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- Since the connection was first made in 1979, the role of zinc in treating such eating disorders as anorexia nervosa and bulimia continues to intrigue researchers.
- Reduced intake of zinc plus an inability to store it in the body can lead to prolonged abnormal eating behaviours.
- Many hospitalised anorexics, who often diet to fatal extremes are zinc deficient - 60% according to a study at the University of Kentucky. The same was true for 40% of bulimic patients. Loss of appetite resulting from too-little zinc for the anorexic is devastating - excessive weight loss, mental dysfunction, thinning hair; dermatitis, and difficulty fighting infection.
- Researchers are investigating a relationship between prenatal zinc deficiency, resulting from the mothers smoking, drinking and general poor nutrition, and the baby's risk for later eating disorders.
- Using zinc supplements to help restore appetite and boost body function is resulting in weight gain and improved health for many anorexics.
Zinc in the environment
ZINC OCCURS NATURALLY IN THE ENVIRONMENT
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- Zinc is the 17th most common element in the earth's crust
- Most rocks contain zinc in varying amounts and zinc exists naturally in air; water and soil. Due to natural weathering and erosion of rocks, soils and sediments together with volcanic eruptions and forest fires, a small but significant fraction of natural zinc is continuously being mobilised and transported in the environment.
- The natural concentrations of zinc in different environments are referred to as background levels and can vary considerably between locations. The animal and plant species within a particular area have evolved to take up zinc from their environment and use it for specific functions in their metabolism. Consequently, all organisms are conditioned to the bio-available zinc concentrations in their environment which are not constant but subject to seasonal variations. Organisms have mechanisms to regulate their internal zinc levels. If uptake levels drop too low, deficiency can occur and adverse effects may be observed.
WHAT HAPPENS TO ZINC IN THE ENVIRONMENT?
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- A major part of zinc present in surface waters ends up deposited in sediments of rivers, estuaries and coastal areas where it binds to organic and inorganic matter; which reduces its mobility and bio-availability.
- Only a finite amount of zinc can be dissolved in a given amount of water depending on many factors such as temperature and pH. It is only the dissolved zinc and not the total zinc that is bio-available and therefore of ecological significance. Zinc bound in suspended organic matter will generally settle so that top sediment layers mirror the zinc levels in the overlying water.
- Studies of ice cores from Greenland show the levels of atmospheric zinc deposition as well as other metals going back thousands of years. Since the late 18th century industrial activity has resulted in anthropogenic (man-made) input of zinc to the environment. The results obtained show that this reached a peak in the 1960's and has markedly decreased since then. This downward trend is a direct result of more efficient emission control within the zinc industry and ambient air zinc levels seem to be returning to pre-industrial levels.
ENVIRONMENTAL RISK ASSESSMENT
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Risk assessment determines the possibility of a substance having an adverse effect on human health or on the functioning of an ecosystem. To achieve this it is necessary to derive two values:
1) The critical level at which adverse effects can be expected and
2) The true exposure to the substance in the environment
If the results of the risk assessment show that the value (1) is greater than the value (2) then there is no risk to man or the environment. If they are equal or (2) is greater; then a risk exists.
WHO/IPCS ZINC TASK FORCE POSITION
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Recently, the International Programme on Chemical Safety (IPCS) a world forum under the auspices of the WHO (World Health Organisation), the ILO (International Labour Organisation) and UNEP (United Nations Environment Programme) - formed a Task Force on Zinc to establish Environmental Health Criteria For Zinc. Among its conclusions, the Task Force states:
"Zinc is an essential element in the environment. The possibility exists for both a deficiency and excess of this metal. For this reason it is important that regulatory criteria for zinc, while protecting against toxicity are not set so low as to drive zinc levels into the deficiency area."
"Galvanizers Association is grateful to the International Zinc Association and the American Zinc Association for their assistance."
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