Zinc

In human living and industry, zinc is ubiquitous.

Zinc is more reactive than iron or steel and is sacrificially utilized to coat iron or steel (galvanization) for protection.  Many structures in our environment may be galvanized e.g.  fencing material and rails, light posts, metal roofs, and car bodies.

Zinc oxide is used as a white pigment in paint.  Zinc sulfate is used to make dyes and pigments.  Zinc chloride is added to wood as a fire retardant or wood preservative. Zinc sulphide is used in the luminescent pigments of hand clocks, x-ray and television screens and luminous paints.  Zinc sulphide crystals are used in infra- red lasers. Zinc dithiocarbamate complexes are used as fungicides in agriculture.  Zinc is added to engine oil.

Powdered zinc is used as anode material in alkaline batteries.  Zinc is molten with various metals to form alloys such as brass (used in communication equipment, hardware, musical instruments, water valves, etc.).  Other zinc alloys are nickel silver, soft aluminium solder, commercial bronze.  Zinc is used in the manufacture of rubber and photocopying products, to make some coins, sheet metal and various industrial and manufacturing materials.    Zinc oxide is used in nuclear reactors and potentially can be used to make nuclear weapons.

In food, zinc is found in minute amounts.  Zinc is an essential dietary trace element. It is involved in the functioning of more than 100 enzymes in our body.  In the processes of DNA synthesis and cell division, zinc is involved with more than 1000 transcription factors without which no end products can be generated. Many proteins bind, and carry zinc. This includes in the brain (where zinc is stored in glutaminergic nerve cells), muscle, bones, kidney, liver, the eye, the prostate, and in semen. Zinc is important in the immune system.

Amongst the important enzymes that cannot work without zinc are carbonic anhydrase and carboxypeptidase.  Carbonic anhydrase is involved in the regulation of the amount of carbon dioxide in the body and maintains the acid base balance of the blood.  Carboxypeptidases are involved in the digestion of proteins in various cells and tissues.  These enzyme are involved in digestion and catabolic modification of proteins, blood clotting, growth factor production, wound healing, reproduction and other processes.  Insulin production requires a carboxypeptidase. Zinc is also needed for the senses of taste and smell.  Daily intake in the diet is necessary as it is not stored in the body.

Some of the foods that contain zinc are oysters, red meat, dark meat chicken, whole grains, fortified cereals, dairy products, pork, nuts such as cashews and almonds, beans, legumes, and lentils including peas. Adults need 8-12 mg of zinc per day.  Dietary supplement zinc tablets can be obtained over the counter.  Safe limits recommended in supplements are between 25 mg and 40 mg.  Zinc is included in daily vitamin tablets as zinc oxide, zinc acetate, or zinc gluconate.  It is an antioxidant indirectly.

Zinc is used in the management of diarrheal disorders and gastroenteritis.  Zinc appears to suppress human rhinovirus which causes common cold.   Zinc acetate or zinc gluconate lozenges are used for common cold by administration of up to 75 mg/day at the onset.  Its side effect includes bad taste and nausea. Intranasal sprays containing zinc products can lead to loss of the sense of smell.  Zinc ointments and powders are used on the skin to protect against sunburn or windburn.  Such preparations are also made to protect against baby diaper rash.  Chelated zinc formulated into toothpaste and mouth washes is used to prevent bad breath.   Zinc pyrithione is added to shampoos to prevent dandruff.  Zinc may be protective on the eye limiting age related macula degeneration.

Zinc is a negative modulator of the a brain inhibitory neurotransmitter GABA  A’s  receptor. Zinc deficiency is linked to major depressive disorders.  Zinc supplements may be helpful in some brain disorders.

Zinc deficiency symptoms include suppressed growth, diarrhoea, disturbance of reproductive processes and impotence, eye and skin lesions, impaired immunity, hair loss, disturbance of cognition and disturbance of carbohydrate utilization.    Some seeds and cereal bran contain phytate which binds zinc and limit its absorption in the gut and this may be significant in people who do not eat meats and have phytate containing foods in their diet.  Zinc deficiency is common in developing countries, especially amongst children.  Zinc supplements can reduce mortality from malnutrition but other factors may be important in the malnutrition states. Mental disorder may be associated with zinc deficiency in elderly persons.

Zinc is an element that is handy for life.  Minute amounts of zinc in our diet is responsible for many important biologic processes.

Theresa Adebola John is a lecturer at Lagos State University College of Medicine (LASUCOM) and an affiliated researcher at the College of Medicine, University of Tennessee, Memphis.  For any comments or questions on this column, please email bolajohnwritings@yahoo.com or call