Zinc Deficiency in Humans

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The techniques used to obtain these data and to define the extended model of zinc metabolism are Important to define changes In zinc metabolism In both normal and pathological states and are particularly useful as an aid In definition of zinc deficiency. Human zinc deficiency has been difficult to Identify because Its symptoms are complex and variable (, 8-11) ranging from Impairments of taste and smell to skin rash and dwarfism. There Is presently no adequate clinical test for the diagnosis of zinc deficiency In humans, which further complicates Its Identification. Zinc content In serum, plasma, red blood cells,urine, saliva or hair have proven Inadequate for specific diagnosis of Individual cases of zinc deflclency(6,8-12). 

In the first report of clinical zinc deficiency in humans (31, 32) the significant dietary consideration, not fully appreciated at that time, was that the village population subsisted primarily on unleavened whole wheat bread or bread and beans and very little animal protein was consumed by this population. 

The report of a WHO Expert Committee (1) emphasized the need for information on the bioavailability of zinc, since the recommended intake was dependent on this important factor. Although zinc deficiency in humans was initially reported from Iran and Egypt, adverse effects of marginal or low intakes of zinc by infants and children have subsequently been reported from other parts of the world (2). Apparently the zinc intakes in Iran and Egypt were adequate but the bioavailability was adversely affected by the high level of phytate and fibre in the diet (2). The zinc content of the modern diet is decreased by the use of refined... 

ALTHOUGH ZINC WAS KNOWN as a required mineral nutrient for the diets of animals, zinc deficiency in humans diets was not recognized until the early 1960s. Individuals consuming an amount of dietary zinc exceeding the usual designated requirement still may show signs of nutritional zinc deficiency. Thus, the adequacy of zinc in humans diets must be evaluated based on the bioavailability of dietary zinc. 

Zinc deficiency in humans is difficult to diagnose because a suitable functional test, or a test for zinc reservoirs, has been lacking, Milne et ai. (1987) documented that a variety of zinc-requiring enzymes of the red blood cell seem to resist the effects of dietary zinc deficiency, but demonstrated that liver alcohol dehydrogenase may be sensitive to the deficiency. The activity of this enzyme was assessed by a functional test — the ethanol tolerance test. The ethanol tolerance test would be expected to be influenced by factors unrelated to zinc status, such as the state of Induchon of the ethanol oxidizing system, and hence may not be the functional test of choice for assessing zinc status. 

A response similar to that noted in the foregoing has been found with experimental deficiency of another mineral — zinc. Zinc deficiency in humans also leaves plasma zinc levels in the normal range, but provokes a decline in white blood cell zinc (Prasad, 1991). 

Zinc deficiency in humans is widespread throughout the world, though it is more prevalent in areas where the population subsists on cereal proteins. Conditioned Zn deficiency is seen in many disease states. Its deficiency during growth periods results... 

Zinc Deficiency in Humans Much of the knoivledge relating to severe zinc deficiency in humans has been derived from studies of individuals born with acrodermatitis enteropathica, a genetic disorder resulting from the impaired uptake and transport of zinc. The signs and symptoms of zinc deficiency are outlined in Table 29.3. 

Reproductive Effects. Daily oral exposure to zinc sulfide to women during the last two trimesters did not cause any complications in pregnancies (Mahomed et al. 1989). No studies were located regarding reproductive toxicity in humans after inhalation or dermal exposure to high levels of zinc. Zinc deficiency in humans has been shown to result in abnormalities of labor, atonic bleeding, pre-term labor, and post-term pregnancies. 

Zinc deficiency in humans may have different origins (see also Sec. 3.1) e.g., by diminution of intake (phytates, fibers), increased needs (pregnancy, lactation, growth), or increased losses (bums, chelating agents). 

Zinc affects other advanced systems, such as development and immunity. Zinc deficiency in humans can delay puberty, which involves an advanced, complex web of signaling throughout the whole organism. This complex problem can be treated with a simple solution spoonfuls of zinc sulfate. 

Zinc deficiency in humans can delay puberty,. .. R. J. P. Williams and R. E. M. Rickaby. Evolution s Destiny Co-evolving Chemistry of the Environment and Life. 2012, RSC Publishing p. 148 In humans it is known that the metamorphosis known as going through puberty, as well as features parallel with it, can be Induced by zinc in food. ... 

The original description of zinc deficiency in humans included lack of pubertal development. Spermatogenesis is a zinc-dependent process. Seminal fluid is particularly rich in zinc, and the sperm appear to accumulate zinc from this source prior to ejaculation. Zinc is also crucial for normal fetal development, and deficiency leads to abnormalities in humans and animals. Maternal zinc deficiency has been linked with pregnancy-associated morbidity, including pre-term delivery. 

The prevalence of marginal zinc deficiency in human populations is unknown because of the lack of a good means of assessing zinc status. Measurement of plasma zinc is straightforward, but it does not serve as a reliable indicator of zinc status. Plasma zinc is a quantitatively minor pool that can be easily influenced by minor shifts in tissue zinc. Plasma concentrations do not fall with decreasing dietary intake, except at very low intakes. Plasma zinc can also be affected by factors unrelated to zinc status (e.g., time of day, stress, and infection). Cellular components of blood can be assayed, but erythrocyte concentrations of zinc are maintained in deficient states and variable results have been found with leucocytes. Hair zinc concentrations may reflect available zinc but will also depend on the rate of hair growth. 

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