Human zinc concentration

Concentrations of zinc in sediments and soils usually do not exceed 200 mg/kg, but can range between 3 and 118 g/kg as a result of human activities (Table 9.3). Atmospheric zinc levels were almost always <1 pg/m3, although they tended to be higher over industrialized areas (Goyer 1986). Average zinc concentrations, in pg/m3 atmosphere, were <0.001 at the South Pole, 0.01 to 0.02 in rural areas of the United States, <0.01 to 0.84 in U.S. cities, and 0.06 to 0.35 at various locations in the United Kingdom (Elinder 1986). 

Zinc concentrations in seminal plasma of domestic chickens (Gallus sp.) are about 100 times lower than those for humans and most other mammals, except sheep. Concentrations of zinc in fowl seminal plasma after in vitro storage of spermatozoa for 24 h at 4°C were near the threshold values toxic to spermatozoa (Blesbois and Mauger 1989), suggesting that poultry spermatozoa normally function near their lower lethal zinc threshold. 

Due to false positives, zinc may confound interpretation of the paralytic shellfish poisoning (PSP) mouse bioassay, one of the routine tests used to measure shellfish safety for human consumption. For example, mice injected intraperitoneally with extracts of healthy oyster tissues showed extreme weakness, a drop in body temperature, cyanosis, and some deaths (McCulloch et al. 1989). The threshold for a toxic PSP response corresponds to a drained tissue zinc level >900 mg/kg FW, and this overlaps the zinc concentration range of 230 to 1650 mg/kg FW (1900 to 9400 mg/kg DW) recorded in healthy oyster soft tissues (McCulloch et al. 1989). 

The balance between excess and insufficient zinc is important. Zinc deficiency occurs in many species of plants and animals, with severe adverse effects on all stages of growth, development, reproduction, and survival. In humans, zinc deficiency is associated with delayed sexual maturation in adolescent males poor growth in children impaired growth of hair, skin, and bones disrupted Vitamin A metabolism and abnormal taste acuity, hormone metabolism, and immune function. Severe zinc deficiency effects in mammals are usually prevented by diets containing >30 mg Zn/kg DW ration. Zinc deficiency effects are reported in aquatic organisms at nominal concentrations between 0.65 and 6.5 pg Zn/L of medium, and in piscine diets at <15 mg Zn/kg FW ration. Avian diets should contain >25 mg Zn/kg DW ration for prevention of zinc deficiency effects, and <178 mg Zn/kg DW for prevention of marginal sublethal effects. 

The fact that zinc is known to be a component of an enzyme carbonic anhydrase leaves no doubt as to its physiological significance. The amount of zinc in erythrocytes seems to parallel the carbonic anhydrase activity.21 The leucocytes which appear to lack carbonic anhydrase contain about 25 times as much zinc (per cell) as do the erythrocytes.20 It seems likely that an investigation of the zinc content of different types of white blood cells coupled with a study of individuals from the standpoint of the different types of white cells present (p. 35) would lead to the discovery of substantial inter-individual differences. The wide spread in the zinc concentrations in three human spleens has already been mentioned (p. 72). A recent study has been made of the intake and excretion of zinc by 13... 

Burgos, G., Amoros, W., Marote, M., Stangoulis, J., Bonierbale, M. (2007). Iron and zinc concentration of native potato cultivars from a human nutrition perspective. J. Sci. Food Agric., 87, 668-675. 

Zinc was confirmed as essential for humans in 1936 and deficiency symptoms were reported in l%l. The size of ihe human fetus is correlated with zinc concentration in the amnintic fluid and habitual low zinc intake in the pregnant female is thought to he related (o several congenital anomalies in humans. Low zinc intakes result in hypogonadism, dwarfism. mental retardation, low serum and red blood cell zinc in humans and animals, and retarded growth and teratogenic effects on the nervous system in rats. 

During the past two decades, essentiality of zinc for man has been established. Deficiency of zinc in man due to nutritional factors and several dls-seased states, has been recognized. A marginal deficiency of zinc appears to be prevalent in many segments of population in developed countries and more severe deficiencies are widespread in many parts of the world. In our experimental human model, a marginal deficiency of zinc was induced by dietary means. Loss of body weight (less than 10% in six months on zinc restricted diet), testicular hypofunction, hyperammonemia and a decrease in plasma, urinary and neutrophil zinc concentration were observed. Changes in zinc dependent enzymes such as deoxythymldine kinase in newly synthesized connective tissue and plasma alkaline phosphatase were also observed as a result of zinc restriction and repletion in our model. 

The purpose of our study was to produce only a mild zlnc-deflclent state In human volunteers. Inasmuch as severe deficiency of zinc may be llfe-threatenlng, as seen In acrodermatitis enteropathlca. Furthermore, It Is the marginal deficiency of zinc that appears to be prevalent and likely to be missed clinically. Our data show that we were successful In producing a mild zlnc-deflclent state In human volunteers by dietary means. Zinc concentration of plasma, erythrocytes, leukocytes, and urine decreased when the dally Intake of zinc was restricted to... 

Changes in the plasma zinc concentration were observed within 4 to 6 weeks and correlated with the severity of dietary zinc restriction. Thus, plasma zinc may be very useful in assessment of zinc status in humans provided infections, myocardial infarction, intravascular hemolysis, and acute stress are ruled out ( ). As a result of infections, myocardial Infarction, and acute stress, zinc from the plasma compartment may... 

Evidence for a similar membrane carrier for zinc in humans has been suggested from studies of zinc uptake in acrodermatitis enteropathica. In 1979, using mucosal samples obtained from acrodermatitis patients, Atherton e reported that, at lower lumenal zinc concentrations, brush border zinc uptake was inhibited in these patients, an effect overcome at higher zinc concentrations (48). As a result of these studies, they suggested the possibility of a membrane associated carrier for zinc in the brush border membrane. In the acrodermatitis enteropathica patients, this carrier could be altered or absent. Their hypothesis is supported by findings in rats by both Davies (38) and by this laboratory (43). 

The zinc content of human milk is highest in colostrum. The average zinc concentration in human milk is approximately 1.5 /Xg/mL. Fresh cow s milk averages 4 /xg/mL, but human milk is a better source of zinc for infant nutrition because of lower bioavailability of zinc in cow s milk. 

Considerable emissions can occur in the vicinity of zinc smelters, and this leads to phytotoxic zinc concentrations in the soil. On occasion, zinc intoxication has been observed in domestic cattle due to high zinc forage grown on such soils, but in general, the accompanying elements such as As, Cd, Mn, and Pb are much more important from the toxicological point of view, especially for humans. 

Nevertheless, the finding of a positive correlation between hair zinc concentration and age, height and weight does suggest that carefully planned studies of zinc accumulation in human hair would be a valuable research adjunct to other indices of zinc nutrition (Anon, 1982a). 

As expected, the frequency distribution of the data has a lognormal, positive skewed, form. The range of the zinc values (0.99-5.69 p-g/ml), but mainly the median (2.85 p-g/ml), are lower than those of humans. According to Minoia et al. (1990), the zinc concentration in human blood ranges from 3.5 to 8.8 p.g/ml, with an average of 6.34 p,g/ml. 

There is a greater difference in the median of zinc concentrations between the sexes, with value higher in males (2.92 p.g/ml). We cannot provide a clear explanation for this and pass the problem to the physiologists. Nevertheless, it could be related to the fact that most of the zinc in the blood is linked to erythrocytes and that some mammal species (e.g. humans) show a sex difference in the number of red cells. 

Hayashi M, Yamamoto K, Yoshimura M, et al. 1993. Cadmium, lead, and zinc concentrations in human fingernails. Bull Environ Contam Toxicol 50(4) 547- 553. 

McBean LD, Mahloudji M, Reinhold JG, et al. 1971. Correlation of zinc concentrations in human plasma and hair. Am J Clin Nutr 24 506-509. 

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