Human Zinc Requirements

Serum copper and zinc levels at diagnosis and hepatocellular carcinoma survival in the Guangdong Liver Cancer Cohort

Copper and zinc are essential micronutrients, whose imbalance may be involved in the development and progression of cancer. However, the role of copper and/or zinc imbalance in the prognosis of hepatocellular carcinoma (HCC) is currently unclear. Our objective was to investigate the association between serum levels of copper, zinc and their ratio (copper/zinc) at diagnosis with HCC survival. We included 989 patients with incident HCC in this prospective cohort study, who were enrolled in the Guangdong Liver Cancer Cohort (GLCC) study within 30 days of diagnosis between September 2013 and February 2017. Serum copper and zinc were measured using inductively coupled plasma mass spectrometry. Primary outcomes were liver cancer-specific survival (LCSS) and overall survival (OS). Cox proportional hazards models were used to calculate the multivariable hazard ratios (HRs) and 95% confidence interval (CI). Higher serum copper levels were strongly associated with worse LCSS (Q4 vs. Q1: HR = 1.87, 95% CI: 1.22-2.86; p < 0.01 for trend) and OS (Q4 vs. Q1: HR = 2.06, 95% CI: 1.36-3.11; p < 0.01 for trend). The calculated copper/zinc ratio was positively associated with LCSS (Q4 vs. Q1: HR = 1.31, 95% CI: 0.89-1.92; P = 0.04 for trend) and OS (Q4 vs. Q1: HR = 1.43, 95% CI: 0.99-2.08; P = 0.01 for trend). No overall associations were observed between serum zinc levels and LCSS or OS in the entire cohort. The results suggest that higher serum copper and copper in relation to zinc levels (i.e., higher copper/zinc ratio) may be associated with worse HCC survival, but serum zinc levels may be not associated with HCC survival.

ZnO Nanoparticles: A Promising Anticancer Agent

Nanoparticles, with their selective targeting capabilities and superior efficacy, are becoming increasingly important in modern cancer therapy and starting to overshadow traditional cancer therapies such as chemotherapy radiation and surgery. ZnO nanoparticles, with their unique properties such as biocompatibility, high selectivity, enhanced cytotoxicity and easy synthesis, may be a promising anticancer agent. Zinc, as one of the major trace elements of the human body and co-factor of more than 300 mammalian enzymes, plays an important role in maintaining crucial cellular processes including oxidative stress, DNA replication, DNA repair, cell cycle progression and apoptosis. Thus, it is evident that an alteration in zinc levels in cancer cells can cause a deleterious effect. Research has shown that low zinc concentration in cells leads to the initiation and progression of cancer and high zinc concentration shows toxic effects. Zinc-mediated protein activity disequilibrium and oxidative stress through reactive oxygen species (ROS) may be the probable mechanism of this cytotoxic effect. The selective localization of ZnO nanoparticles towards cancer cells due to enhanced permeability and retention (EPR) effect and electrostatic interaction and selective cytotoxicity due to increased ROS present in cancer cells show that ZnO nanoparticles can selectively target and kill cancer cells, making them a promising anticancer agent.

Essential interventions for child health

Child health is a growing concern at the global level, as infectious diseases and preventable conditions claim hundreds of lives of children under the age of five in low-income countries. Approximately 7.6 million children under five years of age died in 2011, calculating to about 19 000 children each day and almost 800 every hour. About 80 percent of the world’s under-five deaths in 2011 occurred in only 25 countries, and about half in only five countries: India, Nigeria, Democratic Republic of the Congo, Pakistan and China. The implications and burden of such statistics are huge and will have dire consequences if they are not corrected promptly. This paper reviews essential interventions for improving child health, which if implemented properly and according to guidelines have been found to improve child health outcomes, as well as reduce morbidity and mortality rates. It also includes caregivers and delivery strategies for each intervention. Interventions that have been associated with a decrease in mortality and disease rates include exclusive breastfeeding, complementary feeding strategies, routine immunizations and vaccinations for children, preventative zinc supplementation in children, and vitamin A supplementation in vitamin A deficient populations.

Is the Mediterranean diet adequate to satisfy zinc requirements during adolescence?

OBJECTIVE

To evaluate Zn utilization and status among a sample of Spanish boys consuming a diet based on Mediterranean patterns.

DESIGN

Dietary Zn balance was assessed by means of Zn intake in food and Zn output in faeces and urine as measured by flame atomic absorption spectrophotometry. In addition, biomarkers of Zn status were analysed.

SETTING

Province of Granada, Spain.

SUBJECTS

Twenty healthy male adolescents aged 11-14 years, selected based on medical questionnaire, physical examination and nutritional survey of food habits and lifestyle.

RESULTS

Mean Zn intake was 11·36 (se 0·31) mg/d, 76% of the recommended value for Spanish adolescents. Zn absorption (2·53 (se 0·55) mg/d) was close to the value of 3·0 mg/d required for the growth spurt. Zn status biomarkers and growth parameters were within the normal values for this age group.

CONCLUSIONS

Although a diet based on Mediterranean patterns is associated with factors which can affect Zn absorption, such as high consumption of phytate, its consumption in adequate amounts allows Zn status to be maintained during adolescence. Due to the importance of Zn in preventing growth and behavioural disorders among adolescents, long-term intervention trials to investigate the suitability of the Mediterranean diet with respect to Zn requirements at this time of life are needed.

Explaining the variability in recommended intakes of folate, vitamin B12, iron and zinc for adults and elderly people

Objective

To signal key issues for harmonising approaches for establishing micronutrient recommendations by explaining observed variation in recommended intakes of folate, vitamin B12, Fe and Zn for adults and elderly people.

Design

We explored differences in recommended intakes of folate, vitamin B12, Fe and Zn for adults between nine reports on micronutrient recommendations. Approaches used for setting recommendations were compared as well as eminence-based decisions regarding the selection of health indicators indicating adequacy of intakes and the consulted evidence base.

Results

In nearly all reports, recommendations were based on the average nutrient requirement. Variation in recommended folate intakes (200–400 μg/d) was related to differences in the consulted evidence base, whereas variation in vitamin B12recommendations (1·4–3·0 μg/d) was due to the selection of different CV (10–20 %) and health indicators (maintenance of haematological status or basal losses). Variation in recommended Fe intakes (men 8–10 mg/d, premenopausal women 14·8–19·6 mg/d, postmenopausal women 7·5–10·0 mg/d) was explained by different assumed reference weights and bioavailability factors (10–18 %). Variation in Zn recommendations (men 7–14 mg/d, women 4·9–9·0 mg/d) was also explained by different bioavailability factors (24–48 %) as well as differences in the consulted evidence base.

Conclusions

For the harmonisation of approaches for setting recommended intakes of folate, vitamin B12, Fe and Zn across European countries, standardised methods are needed to (i) select health indicators and define adequate biomarker concentrations, (ii) make assumptions about inter-individual variation in requirements, (iii) derive bioavailability factors and (iv) collate, select, interpret and integrate evidence on requirements.

Effects of maternal zinc supplementation on pregnancy and lactation outcomes

Observational studies in human populations suggest that maternal zinc deficiency during pregnancy may cause adverse pregnancy outcomes for the mother and fetus. Therefore, we reviewed the current evidence from studies of zinc supplementation, with or without other micronutrients, during pregnancy and lactation to assess its impact on maternal, fetal, and infant health. A meta-analysis of supplementation trials indicates a 14% reduction in premature delivery among zinc-supplemented women. Most studies found no significant impact of maternal zinc supplementation on infant birthweight, but a subset of studies conducted in underweight or zinc-deficient women suggests that there may be a positive effect of zinc supplementation in such women. However, the number of relevant studies is limited, and more information is needed to confirm these observations. The results for other pregnancy outcomes are inconsistent, and the number of available studies is small. Likewise, the impact of maternal zinc supplementation during pregnancy on infant postnatal growth and risk of infection is variable, and few studies are available. Thus, more research will be needed to allow definitive conclusions to be drawn, especially for the second half of infancy and later childhood. Studies found no adverse effects of maternal zinc supplementation on iron status during pregnancy. More information is required on other potential adverse effects, particularly with regard to a possible modifying effect of preexisting maternal zinc status. In view of the possible benefits of zinc supplementation for reducing the risk of premature delivery, the possible positive impact of zinc supplementation on infant birthweight among undernourished women, and the lack of reported adverse effects, zinc should be included in maternal supplements given during pregnancy in populations at risk for zinc deficiency.

Effects of dietary zinc supplementation on hen performance, ammonia volatilization, and nitrogen retention in manure

This investigation was undertaken to evaluate the effects of dietary ZnSO4 supplementation on ammonia volatilization and nitrogen retention in hen manure. One hundred twenty, 45-wk-old commercial Leghorn laying hens were sequentially fed diets with 1000, 2000, and 3000 ppm Zn as ZnSO4 (Zn-1000, Zn-2000, and Zn-3000), then followed by two control dietary periods with 114 ppm Zn (Control-1 and Control-2) for a total of five consecutive eight-day experiment periods, respectively. When hens were fed the 1000 and 2000 ppm Zn treatment diets, room ammonia levels were significantly reduced compared to the control diets. Dietary Zn treatments reduced the decomposition of uric acid, resulting in an increase in manure total-N retention compared to the control fed birds. The 1000 ppm Zn supplement had no adverse effects on hen body weight, feed consumption, egg production, egg weight, albumen height, or shell thickness. However, hens fed the diet containing 3000 ppm Zn had significantly depressed body weight, feed consumption, egg production, egg weight, and shell thickness. Zinc levels of egg contents increased linearly as dietary Zn levels increased. These levels in eggs would not be a problem for human consumption because these are much less than the daily Zn recommended dietary allowance. Although land application of such manure will not cause environmental problems or crop toxicity, proper monitoring of soil and crop Zn levels and effective nutrient management planning would be well advised.

Use of stable isotopes to assess the bioavailability of trace elements: a review

The bioavailability (utilization) of trace elements is very variable, depending on the characteristics of the element itself, composition of the diet, gastrointestinal conditions and other physiological factors. To derive dietary recommendations and make use of emerging information on diet-gene interactions relating to nutritional requirements for trace elements, methods for assessing bioavailability are required. The trace elements of particular interest include iron, zinc, selenium and copper because of problems of deficiency, purported links with chronic diseases, and the growing market in fortified foods and supplements. The absorption and subsequent metabolism of trace elements can be monitored using stable isotope tracers, but there are difficulties associated with this approach. Although radioisotopes offer many advantages over stable isotopes, their use is restricted due to safety and ethical issues. The difficulties and limitations of methodologies associated with labelling of trace elements in foods with stable isotopes, design of human studies to generate results that predict bioavailability, and detection and quantification of stable isotopes in biological samples are discussed.

Overview of zinc absorption and excretion in the human gastrointestinal tract

Zinc homeostasis is primarily maintained via the gastrointestinal system by the processes of absorption of exogenous zinc and gastrointestinal secretion and excretion of endogenous zinc. Although these processes modulate net absorption and the size of the readily exchangeable zinc pools, there are limits to the effectiveness of the homeostatic mechanisms of these and other systems. As a result of the interplay of the subcellular regulation of these mechanisms and host, dietary and environmental factors, zinc deficiency is not uncommon, especially on a global basis. This overview briefly reviews current understanding about the subcellular mechanisms of zinc absorption and transport. Factors recognized to affect zinc absorption at the whole body level are reviewed and include the amount and form of zinc consumed; dietary promoters, such as animal protein and low-molecular-weight organic compounds; dietary inhibitors, such as phytate and possibly iron and calcium when consumed as supplements; and physiologic states, such as pregnancy, lactation and early infancy, all of which increase the demand for absorbed zinc. The control of endogenously secreted zinc is less well understood. Available data suggest that the quantity of secreted zinc with each meal may be considerable and that efficient reabsorption is critical to the maintenance of normal zinc balance. Factors that have been proposed to interfere with the normal reabsorption of endogenous zinc include phytate and unabsorbed fat. Understanding of the dietary, physiologic, pathologic and environmental factors that may adversely affect these processes, and therefore zinc homeostasis, will be critical to preventing and treating zinc deficiency in human populations.

Zinc and copper intake and sources in healthy adults living in Bangkok and surrounding districts

The levels of intake and food sources of zinc and copper in 231 20-80 yr old healthy adults living in Bangkok and surrounding districts were determined. Dietary data from 3-d food records collected and validated at Research Center, Ramathibodi Hospital were analyzed. Levels of zinc and copper intake were compared between sexes and age groups (20-39, 40-59, and 60-80 yr). Mean daily zinc and copper intakes (+/-SEM) in men were 6.3+/-0.2 and 1.9+/-0.1 mg, respectively. Mean daily zinc and copper intakes (+/-SEM) estimated in women (5.5+/-0.2 and 1.6+/-0.1 mg) were significantly lower. Higher zinc and copper intakes were found in the younger (20-39 yr) age group of both sexes. This could be explained by higher density and percentage from animal source of both nutrients. Consumption of various types of meat, fish, egg, and milk accounted for 42 and 22%, and rice, the staple food of Thai people for 9 and 23% of total dietary zinc and copper, respectively.

Flow cytometric evaluation of the DNA profile and cell cycle of zinc supplemented human Chang liver cells

Zinc, an essential trace element, is important for normal cell growth. Growing children, especially at puberty, require increased zinc (2.8 mg/day for males and 2.65 mg/day for females). The DNA profile and cell cycle of human Chang liver cells grown in 0-900 mumol/L zinc chloride supplemented serum-free media for 24 h were analyzed using a Coulter flow cytometer. There was no significant difference in the G1, S and G2/M phases between zinc treated cells and control cultures except at 90 and 900 mumol/L zinc chloride. At these two higher dosages, fragmentation of genomic DNA into sub-2N DNA (sub-G1 DNA), generally considered a hallmark of programmed cell death (PCD), was noted. Results of the present study seem to suggest that growth regulation by zinc during growth spurts such as at puberty, could also be influenced by other factors besides its direct effect on DNA synthesis. In addition, high dosages of zinc could be cytotoxic.

[Zinc--update of an essential trace element]

Since the recognition of zinc as an essential trace element in man and animals there has been a remarkable progress in our knowledge of the role of zinc in nutritional physiology, biology and medicine during the last few decades. Highlights in zinc research, mechanisms and homeostatic regulation of zinc absorption, sources of zinc intake, dietary factors and mineral interactions affecting zinc bioavailability are reviewed in the present paper. This is followed by an overview of the biochemical functions of zinc in enzymes, gene expression, endocrinology, immunology and oxidative stress. General signs and metabolic consequences of zinc deficiency as well as excessive intake and toxicity of zinc are summarized. Furthermore, national and international dietary zinc recommendations and different methods to determine the zinc status are discussed.

Zinc supplementation and growth of infants born small for gestational age

To analyze the effect of zinc supplementation on postnatal growth of infants born small for gestational age, we selected 68 infants at birth and followed them monthly for 6 months. They were randomly assigned to a supplemented group (group S, n = 35) receiving 3 mg of Zn (acetate) per day, or to a placebo (group P, n = 33), in a double-blind study. Weight increments in group S were significantly higher than those in group P at 2 months (p < 0.003); z scores showed catch-up growth only in group S. Length increments were also greater in group S than in group P, ending at 6 months were 64.9 +/- 1.8 versus 63.4 +/- 3.5 cm (mean +/- SD; p < 0.01); changes in z scores for 6 months were -1.28 to -0.66 in group S and -1.43 to -1.47 in group P (p < 0.001). Weight-for-length improved similarly in both groups (z score, -2.2 to +0.2). The increase in weight-for-age was higher in group S girls (p < 0.034), ending at 6 months with -0.13 +/- 0.59, versus -0.52 +/- 0.62 in group S boys, -1.15 +/- 0.49 in group P girls, and -1.05 +/- 0.80 in group P boys (+/- SD). More infants in group P received cow milk-based formula before 4 months because of inadequate weight increments. An additive effect on weight increase was observed between Zn supplementation (p < 0.02), exclusive breast-feeding after 4 months of age (p < 0.001), and gender (p < 0.02). Plasma and hair Zn values showed a downward trend, less marked in group S than in group P. We conclude that Chilean infants born small for gestational age have better weight and linear growth during the first 6 months of life if they receive Zn supplementation.

Zinc intake and sources in the US adult population: 1976-1980

OBJECTIVE

To determine levels of intake and food sources of zinc in 1976-80 in US adults between the ages of 19 and 74.

METHODS

Dietary data from 24-hour recalls collected in the Second National Health and Nutrition Examination Survey were analyzed. Levels of zinc intake were compared between demographic subgroups using analysis of variance. The contribution of individual foods to overall zinc consumed was also estimated.

RESULTS

Mean daily intakes (+/- SEM) were 15.5 mg +/- 0.4 and 9.8 mg +/- 0.2 in white men and women, respectively. Mean daily intake estimates in black men and women (12.3 mg +/- 0.8 and 7.8 mg +/- 0.3, respectively) were significantly lower. Lower intakes were observed in women versus men, in older (65 to 74 years) versus younger (19 to 34 years) age groups, and among people with lower versus higher education and income levels. Lower zinc intakes in women and older persons could be mainly attributed to lower overall energy intake compared with gender and age counterparts. However, lower intakes in blacks and persons with lower education or income levels were not explained by differences in energy intake and may be attributed to differences in food selections. Meat and milk products contributed the majority of zinc in recalled diets, accounting for 56 and 60% of total zinc intake in blacks and whites, respectively.

CONCLUSIONS

Levels and sources of zinc intake in 1976-80 were higher than in more recent national surveys, suggesting that zinc intakes may be declining. Population groups more likely to have lower intakes were women, older adults, blacks, and those with lower levels of education and higher poverty levels.

Zinc deficiency in an exclusively breast-fed preterm infant

A formerly premature, exclusively breast-fed infant with severe zinc deficiency syndrome is presented. He showed the characteristic erosive skin changes, including alopecia, as seen in acrodermatitis enteropathica. In addition, he manifested a failure to thrive and irritability. The diagnosis was confirmed by reduced serum levels of zinc (2.3 mumol/l) and alkaline phosphatase (45 U/l). We consider the reduced zinc supply in the breast milk (5.7 mumol/l) as the most likely cause of the disease. Therapy consisted of oral zinc supplements (50 mumol/kg/day) for a period of 30 weeks. Symptoms and laboratory values normalized completely and did not recur on a normal diet.

CONCLUSION

A diet of breast milk can, in rare circumstances, cause insufficient zinc intake resulting in severe zinc deficiency syndrome with characteristic dermatological features. Therapy consists of temporary oral zinc supplementation at a daily dose of 50 mumol/kg.