Zinc in Human Nutrition

Toxicokinetics of zinc oxide nanoparticles and food grade bulk-sized zinc oxide in rats after oral dosages

The increasing application of zinc oxide nanoparticles (ZnO NPs) in consumer products has raised concerns about the potential health risks in human. It is crucial to understand the toxicokinetic information of ZnO NPs, especially the differences between NPs and non-nano form material. This study investigated the toxicokinetic profile of ZnO NPs and food grade bulk-sized ZnO in rats after single or repeated oral dosages. For single oral administration of ZnO suspensions at 350 mg/kgbw, the Zn content in blood and tissues showed no elevation, the majority of ZnO particles were eliminated via feces within 48 h. For repeated oral exposure to ZnO suspensions at 350 mg/kgbw or ZnSO₄ solution at 700 mg/kgbw for 90 days, elevated Zn levels were observed in liver, kidney, and bone in all three treatment groups, the Zn level recovered to normal level in liver and kidney, but not in bone, after a recovery period. ZnO NPs and bulk-sized ZnO showed similarity in toxicokinetics in rats, regardless of exposure duration or gender. ZnO particles shared a similar biodistribution profile with ZnSO₄, and were likely to be absorbed mostly in ionic forms.

Metal concentrations and potential health risk in clam (Meretrix lyrata Sowerby 1851) tissues from East Java Coast, Indonesia

The presence of Hg, Cu, Cr, Cd, Pb, and Zn in clam (Meretrix lyrata) from the East Java Coast (EJC), Indonesia, is reported in this study. Metal levels in clam whole tissues were Zn > Cu > Cr > Pb > Cd > Hg. Cr, Cd, and Pb levels in clam tissue surpassed the tolerated limit for eating and the provisional acceptable weekly intake (PTWI) at numerous places along the EJC. The target hazard quotients (THQs) for Cr, Cd, and Pb were greater than one in several locations, indicating that these metals could be harmful to consumers (particularly non-carcinogenic impacts). Eating clams from this area may be detrimental to human health. Furthermore, target cancer risk (TCR) values for Cr and Cd were greater than 10^-4 in several locations, implying that Cr and Cd could cause cancer in people over the course of a lifetime of exposure.

Concentrations of Metals in Tissues of Cockle Anadara granosa (Linnaeus, 1758) from East Java Coast, Indonesia, and Potential Risks to Human Health

This study reports the presence of Cd, Pb, Zn, Hg, Cu, and Cr in the cockles (Anadara granosa, Linnaeus, 1758) harvested along the East Java Coast, Indonesia. The concentrations of metals were determined by atomic absorption spectrometer and expressed in mg kg⁻¹ wet weight. The concentrations of metals ranged from 0.11 to 0.82 mg kg⁻¹ for Cd, 0.10 to 0.54 mg kg⁻¹ for Pb, 10.22 to 19.04 mg kg⁻¹ for Zn, 0.02 to 1.47 mg kg⁻¹ for Hg, 1.79 to 4.76 mg kg⁻¹ for Cu, and 1.64 to 3.79 mg kg⁻¹ for Cr. The metal concentrations in the whole tissues of cockles were in the order Zn>Cu>Cr>Hg>Cd>Pb. The Cd and Pb levels in cockles were found to be higher than the permissible limit for human consumption according to EC and FAO; the levels of Hg exceeded the EC, Hong Kong, Australia, and Indonesia standards; and the levels of Cr exceeded the Hong Kong standard. The estimated weekly intake (EWI) of cockles indicates that the concentrations of Cd and Hg in the cockle tissues from Gresik were higher than the provisional tolerable weekly intake (PTWI); meanwhile, the concentrations of Cr of cockles from all locations were higher than and close to the PTWI. The THQ values for Cd at Gresik, for Hg at Gresik, Surabaya, and Pasuruan, and for Cr at all locations were higher than one indicating that these metals pose potential noncarcinogenic effects to consumers. Reducing the consumption of cockles should be done in order to minimize the adverse effects of metals especially Cd, Hg, and Cr to human health.

Zinc and selenium nutritional status in vegetarians

A vegetarian diet may have beneficial effects on human health, however when it is not well-balanced may be deficient in some nutrients, as minerals for example. The aim of the present study was to assess the nutritional status of zinc and selenium in vegetarians in the city of São Paulo. A cross-sectional study was performed, and the inclusion criteria were age > or = 18 years, both gender, no use of food or pharmaceutical supplements. Thirty vegetarian, of both genders, mean age of 27 years and 4.5 years of vegetarianism had performed the study, and their mean BMI was 21.5. Zinc plasma concentration was 71 and 62.5 microg/dL for men and women and erythrocyte concentration was 37 microg/gHb for both genders. Selenium concentration was 73.5 and 77.3 microg/L in plasma and 51.4 and 66.9 microg/L in erythrocytes for men and women, respectively. These biochemical values show that, according to the references, selenium blood levels are adequate and zinc concentration in erythrocytes is deficient in the studied population. For this reason, vegetarians should be constantly assessed and receive nutritional support to reduce the effects of inadequate zinc status.

Zinco no plasma e eritrócito de atletas profissionais de uma equipe feminina brasileira de voleibol

OBJETIVO: Avaliar o estado nutricional relativo ao zinco de 12 atletas profissionais do voleibol feminino. MÉTODOS: Determinou-se a concentração de zinco plasmático e eritrocitário por espectrofotometria de absorção atômica, e avaliou-se a ingestão dietética por meio de registro alimentar de três dias, de 12 atletas profissionais do sexo feminino, integrantes de uma equipe de voleibol de Curitiba, PR, na faixa etária de 18 a 24 anos, no ano de 2003. RESULTADOS: Todas as atletas apresentaram valores normais de zinco plasmático. Quanto ao zinco eritrocitário, 100,00% apresentaram valores abaixo da normalidade. Em relação à ingestão dietética de zinco, 83,33% apresentaram adequação. Decréscimos no conteúdo de zinco eritrocitário podem representar o efeito agudo de exercícios prolongados pela utilização enzimática da superóxido dismutase ou anidrase carbônica. CONCLUSÃO: O estado nutricional das atletas relativo ao zinco parece estar inadequado, pois, apesar dos valores normais para a concentração de zinco plasmático, a concentração eritrocitária esteve abaixo da faixa de normalidade para todas as atletas.

Importance of zinc in the elderly: the ZENITH study

The elderly are at nutritional risk as a result of multiple physiological, social, psychological, and economic factors. Physiological functions naturally decline with age, which may influence absorption and metabolism. Social and economic conditions can adversely affect dietary choices and eating patterns. However, at the same time, the nutrient needs of the elderly for certain nutrient (such as vitamins, minerals, proteins) is higher than for younger adults. This article reviews the importance of zinc (Zn) in elderly people, particularly for behavioural and mental function, micronutrient status, immune and antioxidant system, and bone metabolism.

Importância do zinco na nutrição humana

Recentes pesquisas experimentais e clínicas têm reforçado a importância do zinco na saúde humana. O zinco possibilita várias funções bioquímicas, pois é componente de inúmeras enzimas, dentre estas, álcool desidrogenase, superóxido dismutase, anidrase carbônica, fosfatase alcalina e enzimas do sistema nervoso central. Participa na divisão celular, expressão genética, processos fisiológicos como crescimento e desenvolvimento, na transcrição genética, na morte celular, age como estabilizador de estruturas de membranas e componentes celulares, além de participar da função imune e desenvolvimento cognitivo. Sua deficiência pode causar alterações fisiológicas como, hipogonodismo, danos oxidativos, alterações do sistema imune, hipogeusia, danos neuropsicológicos e dermatites. Assim, devido a inúmeras pesquisas referentes a este mineral, este trabalho teve como objetivo mostrar os aspectos atuais sobre a essencialidade do zinco na nutrição humana.

Zinc levels in foods from southeastern Spain: relationship to daily dietary intake

The zinc content of 300 food and 79 beverage samples was determined using flame atomic absorption spectrometry. Sample recoveries, repeatability, and analyses of NIST and CBR-CEC reference materials demonstrated the reliability and accuracy of this technique. Mean zinc concentrations varied from 0.02 microg/ml in fresh water to 71.0 microg/g (fresh weight) in pork liver. The daily dietary intake of zinc for inhabitants of southeastern Spain was estimated to be 10.1 mg (5.5, 4.0, 0.5, and 0.1 mg Zn/day per person from foods of animal and vegetable origin, drinks, and other foods, respectively). Zinc levels found in high protein foods (meat, fish, milk products, eggs, dry fruits, cereals and legumes) were significantly higher than those found in food with a low protein content (vegetables, fruits and drinks) (p < 0.001). A significant linear correlation between zinc levels and the corresponding protein content of cereals, legumes and dry fruits was found (r = 0.754, p < 0.005). Zinc concentrations in milk samples were significantly modified by the thermal treatment (p < 0.001), and the skimming (p < 0.05) and calcium enrichment processes (p < 0.001). Shellfish zinc levels were also significantly higher than those measured in fish (p < 0.05). Mean zinc concentrations found in cheese were statistically higher than those determined in the remaining milk products (p < 0.001). Zinc levels measured in distilled beverages were also statistically lower than those found in fermented ones (p < 0.001).

Serum, zinc and copper levels in children with protein energy malnutrition

Serum zinc and copper were measured by atomic absorption spectrophotometry in 58 children (3 months-5 years); of these, 46 children had protein energy malnutrition (PEM), and 12 children served as controls. The levels of serum zinc and copper were found to be significantly low in children with severe malnutrition (grades III and IV PEM). There was a significant positive correlation between serum zinc and height-for-age (r = 0.8809, p < 0.001). Serum copper was found low only in children exhibiting marked linear growth retardation (height-for-age < 85% of the normal). Hypoalbuminemia (serum albumin < 2.5 g/dl), and anemia (hemoglobin < or = 8.0 g/dl) in malnourished children were associated with significant decline in serum zinc and copper levels, respectively.

The acute phase response to cardiopulmonary bypass in children

The endocrine phase of the stress response to cardiopulmonary bypass in children is known to be subtly different from that seen in adults. The aim of this investigation was to determine whether there are similar differences in the acute phase response. Thirteen children were studied (mean age 2.65 years). Each child had congenital heart disease and underwent corrective cardiac surgery. Blood samples taken two days prior to operation and at 6, 9, 12, 24, 48 and 120 hours after were analysed for C-reactive protein, albumin, caeruloplasmin, zinc and copper concentrations. Metal:carrier protein molar ratios were also calculated. Results demonstrate changes which, although similar to those seen in adults, differed both quantitatively and qualitatively. This is explained by the concept of immaturity leading to a generally poor capacity for protein synthesis and a relative inability to respond to altered circumstances.

Phytate and zinc bioavailability

This review discusses evidence from human studies on the effects of dietary phytate on zinc bioavailability. In vitro and animal experiments have implicated calcium as a potentiating factor because it reacts with phytate, and zinc binds to the precipitate. Magnesium also reacts similarly to calcium, but most studies have not considered this factor. Protein provides amino acids, some of which are able to desorb zinc from the precipitate and improve bioavailability. Some predictive ratios, derived from animal studies, have been directly applied to human studies. The studies reviewed included those on: zinc status of groups, apparent absorption of zinc in normal subjects and ileostomists, true absorption using a stable isotope, plasma tolerance, and the accumulation in the body of a radioisotope. It was concluded that detrimental effects of phytate could be demonstrated on zinc bioavailability, but that the studies had not been designed specifically to demonstrate whether the interactions found in animal studies also apply to humans. It is suggested that more targeted research is required before predictive ratios are used for humans.

Plasma zinc and copper in Paris area preschool children with growth impairment

Plasma zinc, copper, and parameters of growth were measured in a group of 116 French preschool children, 2-5 yr-old from low-income households. Participants were selected on the basis of Z-scores of weight for height (WHZ) and height for age (HAZ). Zinc and copper concentrations of children with growth impairment (GI), defined by a WHZ and/or HAZ < -1 Z-score, were compared to those of age, sex, and ethnic origin matched controls (WHZ and HAZ > -1 Z-score). Mean (+/- SD) plasma zinc concentration was 12.58 +/- 1.84 mumol/L in the GI group, and 13.27 +/- 1.98 mumol/L in the controls. The difference of the means of paired samples was 0.69 +/- 2.34, and by paired t-test the significance reached p = 0.028. This effect was primarily a result of the weight retarded group (WHZ < -1 Z-score, p < 0.009) and to the girls (p < 0.05). There were no significant differences in plasma copper concentrations between groups. These results suggest the presence of marginal zinc deficiency in French preschool children with low weight for height Z-scores.

Zinc absorption in adult men from a chicken sandwich made with white or wholemeal bread, measured by a double-label stable-isotope technique

Eleven fasted adult men consumed a chicken meat sandwich made with white or wholemeal bread, extrinsically labelled with 2 mg 67Zn, on two different occasions. Immediately after eating the sandwich they were given an intravenous injection of 1.5 mg 70Zn. True Zn absorption (which was approximately 7% higher than apparent absorption) was determined by the faecal balance technique by making an allowance for endogenous excretion from measurements of faecal excretion of 70Zn. There was no significant difference in mean true Zn absorption from the white or wholemeal bread sandwich, 33.6 and 25.4% respectively. It was concluded that the substitution of wholemeal for white bread does not reduce Zn absorption from meat-based sandwiches.

The effects of dietary ligands on zinc uptake at the porcine intestinal brush-border membrane

Intestinal brush-border-membrane vesicles were prepared from the porcine small bowel by magnesium precipitation and differential centrifugation, and were functionally intact. The influence of dietary ligands on 65Zn uptake was determined using a 65Zn concentration of 5 microM, an incubation time of 1 min and a reaction temperature of 27 degrees, with a rapid filtration technique. At this low Zn concentration the addition of an excess of folate, histidine or glucose had no effect on Zn uptake. Addition of picolinate, citrate and phytate to the incubation medium significantly reduced Zn uptake at all concentrations of ligand examined. Any inhibitory effects of folic acid in vivo may thus be due to a mucosal rather than lumen interaction. Those ligands inhibiting absorption may have done so through the formation of Zn-ligand complexes, which are either insoluble, or which reduce the binding of Zn to its mucosal receptor. This in vitro model of Zn absorption is useful for comparing the effects of potential Zn-binding ligands in the diet.

Placental zinc in normal and intra-uterine growth-retarded pregnancies

The zinc concentration of placental tissue and cord blood in sixteen mothers who gave birth to normal babies was measured. The blood volume of each placenta was estimated from measurements of haemoglobin concentration of placental homogenate and cord blood, and, by deduction, the Zn content of blood-free placental tissue was calculated. Results were compared with eleven mothers whose fetuses showed a low biparietal diameter velocity between 17 and 28 weeks gestation and with ten mothers who gave birth to intra-uterine growth-retarded (IUGR) babies. As expected, placental weight was significantly correlated with infant birth weight. Blood-free placental tissue contained about four times more Zn (approximately 10 micrograms Zn/g) than cord blood (approximately 2.5 micrograms Zn/ml). Concentrations of Zn in blood-free placental tissue were similar in all three groups, but the cord blood Zn of mothers producing IUGR babies was significantly lower than that of the other two groups. Results of the present study suggested that fetal growth retardation in the mothers studied could not be explained by differences in blood-free placental Zn concentration, but that there may be some association between lower cord blood Zn levels and intra-uterine growth retardation.