At least forty different enzyme systems in the body require the mineral zinc as a cofactor. These enzyme systems are responsible for every major physiological function that necessitates catalytic activity from enzymes at the molecular level. Carbon dioxide exchange rate at the cellular level, for example, would not occur at a rapid enough rates without the presence of adequate amounts of zinc to sustain vital life processes. The bio-chemical synthesis of nucleic acids like the RNA and DNA and protein synthesis also seem to be dependent on the presence of zinc as a co-factor. Zinc is essential for normal growth of cells and is needed in the bio-chemical formation of connective tissues - these two processes again rely on the correct functioning of the nucleic acids and normal protein synthesis in cells. The cells and cellular membranes are also protected by zinc - the mineral may be affecting an antioxidant effect at the cellular level in this case. Changes in the zinc balance in the body is mirrored by changes in the metabolic rate of the other minerals, including copper and magnesium, as well as manganese, and selenium - the metabolism of these minerals responds to the presence of zinc. Zinc may thus be performing a regulatory role with respect to the metabolism of these minerals in the human body. Tissues that are heavily dependent on relatively fast rate of cell proliferation will suffer from a deficiency of zinc as the mineral zinc is considered necessary for all cell and tissue growth. Thus a deficiency of zinc in such tissues can result in delayed healing of wounds, mothers who are deficient in zinc may also give birth to offspring who are born with deformities, zinc deficiencies can induce impaired development in the bones and the muscles, as well as the nervous system, it can delay sexual maturation and cause testicular atrophy and sexual dysfunction, zinc deficiency also induces very rapid loss of hair, as well as deformation in the nails, it can cause skin lesions, induce long term infertility and impaired immune responses. Zinc deficiency can also bring about a reduction in the rate of salivation; it can induce atrophy of the thymus gland and can lead to a greatly reduced absorption of nutrients from food. A persistent loss of appetite, an accompanying loss of the sense of taste as well as smell, growth impairment, disorders like dermatitis, diarrhea and hair fall off as well as long term depression is the long term manifestations of a zinc deficiency in children. Impairment in the absorption of zinc is an inherited defect in cases of acrodermatitis enteropathica - a fatal disease that becomes evident during development and growth. During this disease, a severe deficiency of zinc develops in the individual and induces problems like diarrhea, the loss of hair as well as severe dermatitis, there are lesions in the eyes, these symptoms are accompanied by psychological disturbances and the person's susceptibility to all kinds of infections is greatly heightened. Early infancy when the disease starts to manifest itself, however, affected babies who are breastfed gain some protection from the disease until they are weaned - the human breast milk contains a lot of zinc which is efficiently absorbed and a deficiency usually does not develop in suckling babies. Numerous infections can begin to affect a child with acrodermatitis enteropathica - the normal growth and development of such children is severely affected. Such unfortunate individuals very rarely survive childhood due to the different symptoms that begin to affect them one after the other. Severely deformed infants are usually born to women with these severe zinc deficiencies who have somehow survived into childbearing age. Symptoms of a zinc deficiency in adults are usually similar to the symptoms that affect children - there are some differences as mature bodies react differently to a deficiency of some essential mineral. Adults may suffer from infertility and impaired sexual functioning where younger males and females suffer from retarded sexual development. Impairment in the healing rate of wounds, severe skin lesions, a persistent loss of appetite, a loss of taste and smell, falling hair and an increased susceptibility to infection of all kinds affects people of all ages if they are deficient in levels of the mineral zinc. The status of zinc levels in the human body is affected by many factors which can all contribute to the causative factors behind the deficiency and aggravate the symptoms. The causes bashing the most severe deficiencies of zinc are thought to be the genetic in origin, such as hereditary defects or diseases that can interfere with the proper metabolism of zinc by disrupting the normal biochemical pathways. One example of such a disease is the disorder known as acrodermatitis enteropathica. Reduced blood levels of zinc are also caused by several diseases; this may be due to the increased requirement for the mineral by a body that is weakened with disruptions in the normal biochemical pathways. Among these diseases are included problems like severe alcoholism, conditions such as atherosclerosis and chronic coetaneous ulcers, liver cirrhosis, people affected by Down's syndrome or dwarfism often suffer from deficiencies, as do people affected by lung cancer or leukemia, zinc deficiencies are also evident in those affected by myocardial infarction and pulmonary infection. Zinc deficiencies are also normally seen in individuals affected by tuberculosis, in those suffering from diabetes, those affected by hepatitis, those affected by uremia, those suffering from burns, from bacterial and viral infections and all kinds of acute inflammatory diseases. Zinc deficiencies are also seen in people affected by malabsorption syndromes, by steatorrhea and those who have suffered loss of blood loss, people affected by schizophrenia and thyrotoxicosis may also suffer from zinc deficiency. Besides deficiency of zinc in foods and disease states, several other factors can affect the levels of zinc in the body. In the average human body, the absorption of the mineral zinc can vary from twenty to eighty percent, but is normally only about twenty to thirty percent in most individuals. A zinc deficiency leads to an increase in the rate of absorption of zinc from the food, this occurs as the body tries to permit more zinc into the blood stream. This effect can also come about based on the content of the diet irrespective of the amount of zinc. The absorption of zinc is also decreased by high fiber diets. The absorption of zinc is also apparently inhibited by the presence of phytates - phosphorus compounds - present in cereal grains. This is the reason for the greater "bio-availability" of zinc sourced from animal foods - these are typically low in fiber and phytates - compared to plant foods. What is not known is the precise amount of zinc absorption inhibited by the fiber found in cereals and vegetables. The absence of any effect from such fibers has been shown in some clinical studies. This factor is no reason to cut off the fiber from the diet, even if the fiber can decrease zinc absorption - plant based fiber is necessary for human health and is comparable to zinc in its usefulness. Zinc absorption in the body is also impaired by lemon juice. Zinc requirements in the body may also be increased by the constant consumption of high protein diets. Zinc deficiency can also be due to the use of several types of medications, these include chelating agents of all kinds, various diuretics, hormones like the corticosteroids and oral contraceptive pills. Zinc also prevents toxicity arising from the presence of cadmium in the body. This also depletes the level of zinc as cadmium also uses up zinc if present in the body in high amounts. Zinc requirements tend to increase if the diet is high in cadmium. The cadmium in foods is unfortunately not eliminated during the processing and refining of food products, while the same refinement and processing of foods removes all the zinc. The zinc requirement of the body is thus increased for all individuals mainly relying on a diet of processed foods. The absorption of zinc from food is dictated by the requirement of the body for the mineral at any particular time. During every meal the human body actually gets two chances to absorb zinc from the food, the first opportunity is from the foods being eaten - if they contain some zinc, the second opportunity is zinc absorbed from the digestive juices secreted in the pancreas. The presence of certain substances in the digestive juices as a matter of fact, greatly enhances the absorption of zinc from the food. The rate of absorption of zinc is also aided by absorption in the intestines and these are not "passive" when it comes to absorption of zinc. The needs of the body can in fact increase or decrease the efficiency of zinc absorption and the rate of intake is dependent on the needs of the body for the mineral at any particular time. Seafood is the best natural sources for the mineral zinc - particularly oysters and herring, zinc is also found abundantly in organ meats like the liver, it is also found in good amounts in meats as well as milk, in eggs, in all types of nuts, in all kinds of legumes and in brewer's yeast. Zinc is available in the highest quantities in breast milk - this is the best source of zinc for infants. This is because zinc obtained from breast milk is easily absorbed that it has been used for supplementing the mineral zinc in cases of impaired zinc utilization and malabsorption problems. Various other compounds also have zinc as a component, and these are available as supplements - compounds like zinc sulfate, zinc gluconate and others are commonly used for supplemental purposes. The most common form of zinc used in medical experiments is zinc sulfate, this is despite the fact that zinc sulfate irritates the stomach. Supplemental zinc in the form of zinc acetate is also commonly used and seems to cause lesser problems than other compound forms of the mineral. Supplements of zinc sulfate can be eaten with the meal to lower the chances of stomach irritations. Marginal deficiencies of zinc seem to affect many more low income pregnant women and pregnant teenagers than it does other people - such people are more susceptible to a deficiency in zinc than others. The outcome of a pregnancy in these groups of people can be improved by supplementing with 25 to 30 mg of zinc daily. Less than the recommended daily allowance of zinc is found in the average American diet. Such dietary gaps in the intake of zinc can be corrected by the use of a low dose supplement of about 15 mg daily. There is a greater chance of a zinc deficiency affecting long term alcoholics and other individuals suffering from sickle cell anemia. Such a deficiency can also affect those with malabsorption problems and people affected by chronic kidney disease.
A deficiency in zinc can be prevented by taking moderate doses of zinc at 15 to 25 mg. The use of higher dosage amounts of up to 50 mg thrice per day are meant only for the treatment of specific health conditions affecting a person, such high doses are also consumed only under the supervision of a qualified nutritionally oriented doctor experienced in designing supplementation regimens of zinc. Zinc lozenges are also used for alleviating the symptoms of a cold; such lozenges provide about 15 to 25 mg of zinc in the form zinc gluconate and can generally be used many times throughout the course of a day by patients suffering from common cold.
An intake of zinc in excess of 300 mg daily can reportedly lead to the impairment of the immune function, and affect long term health. Physical symptoms such as severe stomach pain, spells of nausea, irritation in the mouth and a bad taste in the mouth has been reported by some people who used zinc lozenges. Zinc has no known side effect when used in the form of a topical remedy, and no side effects when consumed in the recommended amounts. Zinc supplements must be avoided by those affected by Alzheimer's disease according to the evidence garnered from preliminary research. Zinc supplements have more recently been found to lead to an improved mental functioning as demonstrated by preliminary evidence from four patients during a clinical investigation. Someone considers to be the most respected clinical researcher on zinc in the world concluded that the use of zinc does not induce nor exacerbate Alzheimer's disease during a convincing review of the connection between zinc and Alzheimer's disease. The absorption rate of copper in the body is also inhibited by zinc, this effect of zinc on the absorption of copper can lead to severe anemia and in lower levels of HDL cholesterol - the "good" cholesterol - in the body. When zinc supplements are used for more than a few days, it must be accompanied by an increase in the intake of copper - with the exception of individuals suffering from Wilson's disease. Copper is often included in the formulation of many marketed zinc supplements, this is done to prevent the inhibition of copper by the high doses of zinc.