Assessment of the trace element status of individuals and populations: the example of zinc and copper

Assessment of trace element and mineral levels in students from Turkmenistan in comparison to Iran and Russia

THE OBJECTIVE

Of the present study was to assess essential trace element and mineral levels in serum, hair, and urine of healthy first-year students from Turkmenistan (n = 73) in comparison to students from Iran (n = 78) or Russia (n = 95).

MATERIALS AND METHODS

Examination of foreign students was performed within two days after arrival to Russia during medical examination prior admission to RUDN University. Serum, hair, and urine trace element and mineral levels were assessed with inductively coupled plasma-mass spectrometry (ICP-MS).

RESULTS

The data demonstrate that the levels of trace elements and minerals in students from Turkmenistan share high similarity to elemental profiles of students from Iran. In comparison to students from Russia, subjects originating from Iran and Turkmenistan are characterized by lower serum cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), molybdenum (Mo), selenium (Se), vanadium (V), zinc (Zn) levels, higher urinary Cr, Cu, Fe, Mn, V, and Zn, lower urinary Co and hair Mo, Se, and Zn content. Concomitantly, students from Turkmenistan were characterized by lower urinary Cr and Cu, serum Cu and V levels, higher circulating Zn concentration, as well as the lower hair Cr, Cu, iodine (I) and magnesium (Mg) content in comparison to Iranian subjects. The discriminant analysis demonstrated that hair, serum, and urinary trace element and mineral levels contributed to complete discrimination between the groups of students from different countries.

CONCLUSIONS

The high similarity of trace element and mineral status of students from Turkmenistan and Iran is expected to be mediated by similar geochemical conditions in the bordering countries.

Copper and Trace Elements in Gallbladder form Patients with Wilson's Disease Imaged and Determined by Synchrotron X-ray Fluorescence

Investigations about suspected tissue alterations and the role of gallbladder in Wilson’s disease (WD)—an inherited genetic disease with impaired copper metabolism—are rare. Therefore, tissue from patients with genetically characterised WD was investigated by microscopic synchrotron X-ray fluorescence (µSRXRF). For two-dimensional imaging and quantification of elements, X-ray spectra were peak-fitted, and the net peak intensities were normalised to the intensity of the incoming monochromatic beam intensity. Concentrations were calculated by fundamental parameter-based program quant and external standardisation. Copper (Cu), zinc (Zn) and iron (Fe) along with sulphur (S) and phosphorus (P) mappings could be demonstrated in a near histological resolution. All these elements were increased compared to gallbladder tissue from controls. Cu and Zn and Fe in WD-GB were mostly found to be enhanced in the epithelium. We documented a significant linear relationship with Cu, Zn and sulphur. Concentrations of Cu/Zn were roughly 1:1 while S/Cu was about 100:1, depending on the selected areas for investigation. The significant linear relationship with Cu, Zn and sulphur let us assume that metallothioneins, which are sulphur-rich proteins, are increased too. Our data let us suggest that the WD gallbladder is the first in the gastrointestinal tract to reabsorb metals to prevent oxidative damage caused by metal toxicity.

Trace metals and animal health: Interplay of the gut microbiota with iron, manganese, zinc, and copper

Metals such as iron, manganese, copper, and zinc are recognized as essential trace elements. These trace metals play critical roles in development, growth, and metabolism, participating in various metabolic processes by acting as cofactors of enzymes or providing structural support to proteins. Deficiency or toxicity of these metals can impact human and animal health, giving rise to a number of metabolic and neurological disorders. Proper breakdown, absorption, and elimination of these trace metals is a tightly regulated process that requires crosstalk between the host and these micronutrients. The gut is a complex system that serves as the interface between these components, but other factors that contribute to this delicate interaction are not well understood. The gut is home to trillions of microorganisms and microbial genes (the gut microbiome) that can regulate the metabolism and transport of micronutrients and contribute to the bioavailability of trace metals through their assimilation from food sources or by competing with the host. Furthermore, deficiency or toxicity of these metals can modulate the gut microenvironment, including microbiota, nutrient availability, stress, and immunity. Thus, understanding the role of the gut microbiota in the metabolism of manganese, iron, copper, and zinc, as well as in heavy metal deficiencies and toxicities, and vice versa, may provide insight into developing improved or alternative therapeutic strategies to address emerging health concerns. This review describes the current understanding of how the gut microbiome and trace metals interact and affect host health, particularly in pigs.

Zn homeostasis in genetic models of Parkinson's disease in Caenorhabditis elegans

While the underlying mechanisms of Parkinson's disease (PD) are still insufficiently studied, a complex interaction between genetic and environmental factors is emphasized. Nevertheless, the role of the essential trace element zinc (Zn) in this regard remains controversial. In this study we altered Zn balance within PD models of the versatile model organism Caenorhabditis elegans (C. elegans) in order to examine whether a genetic predisposition in selected genes with relevance for PD affects Zn homeostasis. Protein-bound and labile Zn species act in various areas, such as enzymatic catalysis, protein stabilization pathways and cell signaling. Therefore, total Zn and labile Zn were quantitatively determined in living nematodes as individual biomarkers of Zn uptake and bioavailability with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) or a multi-well method using the fluorescent probe ZinPyr-1. Young and middle-aged deletion mutants of catp-6 and pdr-1, which are orthologues of mammalian ATP13A2 (PARK9) and parkin (PARK2), showed altered Zn homeostasis following Zn exposure compared to wildtype worms. Furthermore, age-specific differences in Zn uptake were observed in wildtype worms for total as well as labile Zn species. These data emphasize the importance of differentiation between Zn species as meaningful biomarkers of Zn uptake as well as the need for further studies investigating the role of dysregulated Zn homeostasis in the etiology of PD.

Determination of major and trace element variability in healthy human urine by ICP-QMS and specific gravity normalisation

Sixty five urine samples obtained during one or two non-consecutive days from 10 healthy individuals were analysed for major (Na, Mg, K, Ca) and trace (Co, Cu, Zn, As, Rb, Sr, Mo and Pb) element concentrations. Following microwave digestion, the analyses were carried out using ICP-QMS (inductively coupled plasma quadrupole mass spectrometry) incorporating a collision/reaction cell. Repeat analyses of quality control samples show that the procedure produces unbiased results and is well suited for routine urinalysis of the investigated elements. Concentrations were normalised using specific gravity (SG) and the resultant decrease in variability supports previous conclusions that SG-normalisation appropriately corrects for differences in urine dilution. The elemental concentrations of the individual urine samples show large differences in dispersion. Most variable are As, Co and Zn, with CVs (coefficients of variation) of >75%. The major elements as well as Rb, Sr and Mo display intermediate variability, whilst Cu and Pb have the least elemental dispersion with CV values of about 30%. A detailed assessment shows that the overall elemental variability is governed both by differences between individuals and variations for a single individual over time. Spot urine samples exhibit elemental concentrations that, on average, resemble the daily mean values to within about 30% for all elements except K and Rb. Diet-related changes in urinary element concentration are most prominent for Mg, K, Co, Rb and Pb. The concentrations of Co, As and Rb appear to vary systematically with gender but this may primarily reflect co-variance with specific diets.

Urinary element concentrations were quantified by ICP-QMS and variations over time, between individuals and with gender and diet were assessed.

Zinc and infant nutrition

Zinc is essential for a wide variety of cellular processes in all cells. It is a critical dietary nutrient, particularly in the early stages of life. In the early neonatal period, adequate sources of zinc can be obtained from breast milk. In rare circumstances, the mammary gland produces zinc deficient milk that is potentially lethal for exclusively breast-fed infants. This can be overcome by zinc supplementation to the infant. Alterations to key zinc transporters provide insights into the mechanisms of cellular zinc homeostasis. The bioavailability of zinc in food depends on the presence of constituents that may complex zinc. In many countries, zinc deficiency is a major health issue due to poor nourishment. Young children are particularly affected. Zinc deficiency can impair immune function and contributes to the global burden of infectious diseases including diarrhoea, pneumonia and malaria. Furthermore, zinc deficiency may extend its influence across generations by inducing epigenetic effects that alter the expression of genes. This review discusses the significance of adequate zinc nutrition in infants, factors that influence zinc nutrition, the consequences of zinc deficiency, including its contribution to the global burden of disease, and addresses some of the knowledge gaps in zinc biology.

Prediction of Serum Zinc Levels in Mexican Children at 2 Years of Age Using a Food Frequency Questionnaire and Different Zinc Bioavailability Criteria

BACKGROUND

The 2006 Mexican National Health and Nutrition Survey documented a prevalence of zinc deficiency of almost 30% in children under 2 years of age.

OBJECTIVE

We sought to validate a food frequency questionnaire (FFQ) for quantifying dietary bioavailable zinc intake in 2-year-old Mexican children accounting for phytic acid intake and using serum zinc as a reference.

METHODS

This cross-sectional study was nested within a longitudinal birth cohort of 333 young children in Mexico City. Nonfasting serum zinc concentration was measured and dietary zinc intake was calculated on the basis of a semiquantitative FFQ administered to their mothers. The relationship between dietary zinc intake and serum zinc was assessed using linear regression, adjusting for phytic acid intake, and analyzed according to two distinct international criteria to estimate bioavailable zinc. Models were stratified by zinc deficiency status.

RESULTS

Dietary zinc, adjusted for phytic acid intake, explained the greatest proportion of the variance of serum zinc. For each milligram of dietary zinc intake, serum zinc increased on average by 0.95 μg/dL (0.15 μmol/L) (p = .06). When stratified by zinc status, this increase was 0.74 μg/dL (p = .12) for each milligram of zinc consumed among children with adequate serum zinc (n = 276), whereas among those children with zinc deficiency (n = 57), serum zinc increased by only 0.11 μg/dL (p = .82).

CONCLUSIONS

A semiquantitative FFQ can be used for predicting serum zinc in relation to dietary intake in young children, particularly among those who are zinc-replete, and when phytic acid or phytate intake is considered. Future studies should be conducted accounting for both zinc status and dietary zinc inhibitors to further elucidate and validate these findings.

Biomarkers of Nutrition for Development (BOND)-Zinc Review

Zinc is required for multiple metabolic processes as a structural, regulatory, or catalytic ion. Cellular, tissue, and whole-body zinc homeostasis is tightly controlled to sustain metabolic functions over a wide range of zinc intakes, making it difficult to assess zinc insufficiency or excess. The BOND (Biomarkers of Nutrition for Development) Zinc Expert Panel recommends 3 measurements for estimating zinc status: dietary zinc intake, plasma zinc concentration (PZC), and height-for-age of growing infants and children. The amount of dietary zinc potentially available for absorption, which requires an estimate of dietary zinc and phytate, can be used to identify individuals and populations at risk of zinc deficiency. PZCs respond to severe dietary zinc restriction and to zinc supplementation; they also change with shifts in whole-body zinc balance and clinical signs of zinc deficiency. PZC cutoffs are available to identify individuals and populations at risk of zinc deficiency. However, there are limitations in using the PZC to assess zinc status. PZCs respond less to additional zinc provided in food than to a supplement administered between meals, there is considerable interindividual variability in PZCs with changes in dietary zinc, and PZCs are influenced by recent meal consumption, the time of day, inflammation, and certain drugs and hormones. Insufficient data are available on hair, urinary, nail, and blood cell zinc responses to changes in dietary zinc to recommend these biomarkers for assessing zinc status. Of the potential functional indicators of zinc, growth is the only one that is recommended. Because pharmacologic zinc doses are unlikely to enhance growth, a growth response to supplemental zinc is interpreted as indicating pre-existing zinc deficiency. Other functional indicators reviewed but not recommended for assessing zinc nutrition in clinical or field settings because of insufficient information are the activity or amounts of zinc-dependent enzymes and proteins and biomarkers of oxidative stress, inflammation, or DNA damage.

A historical review of progress in the assessment of dietary zinc intake as an indicator of population zinc status

Dietary components influencing zinc (Zn) bioavailability were implicated in the first cases of human Zn deficiency in the Middle East in the 1960s. It was not until the 1980s that isotope tracer studies in humans quantified the effects of the type and/or quantity of Zn, protein, iron, and phytate (myo-inositol hexaphosphate) on Zn absorption in humans and confirmed the dose-dependent inhibitory effect of phytate on Zn absorption. This led to further analysis of the Zn and phytate content of foods. The use of phytate-to-Zn molar ratios as likely estimates of absorbable dietary Zn followed together with an assessment of their relationship with Zn biomarkers in low-income countries (LIC). In the 1990s, increasing knowledge of factors governing Zn-absorption diets led to refinements of Zn requirements and algorithms to estimate dietary Zn bioavailability. Their use highlighted that inadequate Zn intake from plant-based diets were a major etiological factor in morbidity and stunting in LIC, prompting the need to identify indicators of the population's Zn status. Major advances in analyses of dietary data pioneered by Beaton in 1980s led to the endorsement in 2007 of a dietary Zn indicator based on the prevalence of the population with usual Zn intake below the estimated average requirement for Zn. Risk of Zn deficiency is a public health concern when the prevalence of inadequate Zn intake is >25%. Recent findings that Zn bioavailability from high-phytate, whole-day diets is lower than previous estimates suggest that revision of Zn estimated average requirement for LIC may be warranted.

Bioavailability and preliminary toxicity evaluations of alumina nanoparticles in vivo after oral exposure

Alumina nanoparticles (NPs) are among the most important nanomaterials and are widely used in diverse areas. In this study, we evaluated the bioavailability and toxicity of alumina NPs in mice after oral exposure, compared with traditional alumina powder. Our results indicated that negligible alumina NPs were absorbed post-exposure and alumina NPs did not influence the balance of essential trace elements, including Fe, Cu and Zn. Preliminary toxicological evaluations suggested that alumina NPs were of low toxicity. The body weights were similar among the mice exposed to alumina NPs, alumina powder and 0.9% NaCl aqueous solution. The low toxicity was also indicated by the unchanged serum biochemical parameters. The implications related to the ongoing safety evaluations and applications of alumina NPs are discussed.

Dosing and monitoring of trace elements in long-term home parenteral nutrition patients

BACKGROUND

Trace elements (TEs) dosing and monitoring in home parenteral nutrition (PN) patients vary with their underlying conditions.

METHODS

This retrospective observational study evaluated parenteral TE dosing, serum TE concentrations and monitoring, and dose-concentration relationships between TE doses and serum TE concentrations in 26 adult and adolescent home PN patients.

RESULTS

There was a total of 40,493 PN days. Average parenteral zinc doses of 9.1 mg/d and 7.6 mg/d resulted in the majority of serum zinc concentrations (90%) within normal range in patients with and without short bowel syndrome (SBS), respectively. Selenium at about 70 mcg/d resulted in about 60% of serum selenium concentrations within normal range, with 38% of values below normal in patients with and without SBS alike. Copper at 1 mg/d resulted in 22.5% of serum copper concentrations above the normal range. The majority of serum manganese (94.6%) and chromium (96%) concentrations were elevated. Serum TE concentrations were infrequently monitored. Significant relationships existed between doses and serum concentrations for zinc (P < .0001), manganese (P = .012), and chromium (P < .0001) but not for selenium or copper.

CONCLUSIONS

TE doses in home PN should be individualized and adjusted based on regular monitoring of TE status. In long-term home PN patients, higher zinc and selenium doses may be necessary to maintain their normal serum concentrations. Lower copper doses and restrictions of manganese and chromium supplementation may be needed to avoid their accumulation. Relationships between TE doses and serum TE concentrations vary for each TE and underlying clinical conditions.

Marginal zinc deficiency in pregnant rats impairs bone matrix formation and bone mineralization in their neonates

Zinc (Zn) deficiency during pregnancy may result in a variety of defects in the offspring. We evaluated the influence of marginal Zn deficiency during pregnancy on neonatal bone status. Nine-week-old male Sprague-Dawley rats were divided into two groups and fed AIN-93G-based experimental diets containing 35 mg Zn/kg (Zn adequately supplied, N) or 7 mg Zn/kg (low level of Zn, L) from 14-day preconception to 20 days of gestation, that is, 1 day before normal delivery. Neonates were delivered by cesarean section. Litter size and neonate weight were not different between the two groups. However, in the L-diet-fed dam group, bone matrix formation in isolated neonatal calvaria culture was clearly impaired and was not recovered by the addition of Zn into the culture media. Additionally, serum concentration of osteocalcin, as a bone formation parameter, was lower in neonates from the L-diet-fed dam group. Impaired bone mineralization was observed with a significantly lower content of phosphorus in neonate femurs from L-diet-fed dams compared with those from N-diet-fed dams. Moreover, Zn content in the femur and calvaria of neonates from the L-diet group was lower than that of the N-diet-fed group. In the marginally Zn-deficient dams, femoral Zn content, serum concentrations of Zn, and osteocalcin were reduced when compared with control dams. We conclude that maternal Zn deficiency causes impairment of bone matrix formation and bone mineralization in neonates, implying the importance of Zn intake during pregnancy for proper bone development of offspring.

Zinc influences innate immune responses in children with enterotoxigenic Escherichia coli-induced diarrhea

Information is limited on the effect of zinc on immune responses in children with diarrhea due to enterotoxigenic Escherichia coli (ETEC), the most common bacterial pathogen in children. We studied the immunological effect of zinc treatment (20 mg/d) and supplementation (10 mg/d) in children with diarrhea due to ETEC. A total of 148 children aged 6-24 mo were followed up for 9 mo after a 10-d zinc treatment (ZT; n = 74) or a 10-d zinc treatment plus 3-mo supplementation (ZT+S; n = 74), as well as 50 children with ETEC-induced diarrhea that were not treated with zinc (UT). Fifty control children (HC) of the same age group from the same location were also studied. Serum zinc concentrations were higher in both the ZT (P < 0.001) and ZT+S groups (P < 0.001) than in the UT group but did not differ from the HC group. We found higher serum complement C3 immediately after zinc administration in both ZT (P < 0.001) and ZT+S (P < 0.001) groups than in the UT group. Phagocytic activity in children in both ZT (P < 0.01) and ZT+S (P < 0.01) groups was greater than in the UT group. However, oxidative burst capacity was lower in zinc-receiving groups (ZT, P < 0.001 and ZT+S, P < 0.001) than in the UT group. The naïve:memory T cell ratio in both ZT (P < 0.05) and ZT+S (P < 0.01) groups was higher than in the UT group from d 2 to 15. Increased responses, including complement C3, phagocytic activity, and changes in T cell phenotypes, suggest that zinc administration enhances innate immunity against ETEC infection in children.

The ubiquitous role of zinc in health and disease

OBJECTIVE

To review zinc physiology and pathophysiology and the importance of zinc toxicity and deficiency in veterinary patients.

DATA SOURCES

A review of human and veterinary medical literature.

HUMAN DATA SYNTHESIS

There is a significant amount of original research in humans and animals on the role of zinc in multiple organ systems. There is also significant data available on human patients with zinc abnormalities.

VETERINARY DATA SYNTHESIS

Zinc deficiency has been studied in dogs with genetic disease and dietary deficiency leading to dermatological disease and immune deficiency. Zinc toxicity has been described after ingestion of metallic foreign bodies containing zinc.

CONCLUSIONS

Historically, the role of zinc in health and disease has been studied through patients with toxicity or severe deficiency with obvious clinical signs. As the ubiquitous contribution of zinc to structure and function in biological systems was discovered, clinically significant but subtle deficiency states have been revealed. In human medicine, mild zinc deficiencies are currently thought to cause chronic metabolic derangement leading to or exacerbating immune deficiency, gastrointestinal problems, endocrine disorders, neurologic dysfunction, cancer, accelerated aging, degenerative disease, and more. Determining the causal relationships between mild zinc deficiency and concurrent disease is complicated by the lack of sensitive or specific tests for zinc deficiency. The prevalence of zinc deficiency and its contribution to disease in veterinary patients is not well known. Continued research is warranted to develop more sensitive and specific tests to assess zinc status, to determine which patients are at risk for deficiency, and to optimize supplementation in health and disease.

CD4+ T-cell responses to an oral inactivated cholera vaccine in young children in a cholera endemic country and the enhancing effect of zinc supplementation

Immunization of young children with the oral inactivated whole cell cholera vaccine Dukoral((R)) containing recombinant cholera toxin B subunit (CTB) induces antibody responses which can be further enhanced by zinc supplementation. We have investigated if immunization with the cholera vaccine induces specific T-cell responses in young children and also whether zinc supplementation influences these responses. Bangladeshi children (10-18 months old) received vaccine alone, vaccine together with zinc supplementation or only zinc. T-cell blast formation indicating a proliferative response was analyzed by the flow cytometric assay of cell-mediated immune response in activated whole blood (FASCIA) and cytokines were measured by ELISA. Stronger T-cell responses were detected if a modified CTB molecule (mCTB) with reduced binding to GM1 ganglioside was used for cell stimulation compared to normal CTB. After vaccination, CD4+ T cells responded to mCTB with significantly increased blast formation (P<0.01) and IFN-gamma production (P<0.05) compared to before vaccination. No responses to mCTB were detected in children receiving zinc alone (P>0.05). The IFN-gamma production was significantly higher (P<0.01) but the blast formation comparable (P>0.05) in children receiving zinc plus vaccine compared to in children receiving vaccine alone. The vibriocidal antibody responses induced by the vaccine were also significantly higher in children receiving zinc supplementation (P<0.001). Our results thus show that oral cholera vaccination induces a Th1 T-cell response in young children, and that the IFN-gamma as well as the vibriocidal antibody responses can be enhanced by zinc supplementation.

The impact of rapid economic growth and globalization on zinc nutrition in South Korea

Objective

Zn deficiency may be widespread in Asian countries such as South Korea. However, dietary habits have changed in response to rapid economic growth and globalization. Zn nutrition in South Koreans has therefore been assessed during a period (1969–1998) of unprecedented economic growth.

Design and methods

Cross-sectional food consumption data from the Korean National Nutrition Survey Reports (KNNSR) of South Korea at four separate time points (1969, 1978, 1988 and 1998) were used to calculate Zn, Ca and phytate intakes using various food composition tables, databases and literature values. Nutrient values in local foods were cited from their analysed values.

Results

Average Zn intake was 5·8, 4·8 and 5·3 mg/d for 1969, 1978 and 1988 respectively, increasing to 7·3 mg/d in 1998 (73 % of the Korean Dietary Reference Intake). The phytate:Zn molar ratio decreased from 21 to 8 during the study period. Dietary Zn depletion due to marked decreases in cereal consumption, particularly barley which has a low Zn bioavailability, was counterbalanced by marked increases in the consumption of meat and fish, which are also Zn-rich foods. Reduced phytate consumption coincident with increased Zn intake suggests that Zn bioavailability also improved, particularly by 1998.

Conclusions

Although total Zn intake was not greatly affected over the initial period of economic growth in South Korea (1969–1988), Zn contributions from different food sources changed markedly and both Zn intake and potential bioavailability were improved by 1998. The study may have implications for Zn nutrition in other Asian countries currently experiencing rapid economic growth.

Methods of assessment of zinc status in humans: a systematic review

BACKGROUND

Zinc is an essential micronutrient for human health and has numerous structural and biochemical roles. The search for a reliable, sensitive, and specific index of zinc status has been the subject of considerable research, which has resulted in the identification of a number of potentially useful biomarkers.

OBJECTIVE

The objective was to assess the usefulness of biomarkers of zinc status in humans.

DESIGN

The methods included a structured search strategy using Ovid MEDLINE, EMBASE (Ovid), and the Cochrane Library CENTRAL databases; formal inclusion and exclusion criteria; data extraction into an Access database; quality and validity assessment; and meta-analysis.

RESULTS

Data on 32 potential biomarkers from 46 publications were analyzed. Plasma zinc concentration responded in a dose-dependent manner to dietary manipulation in adults, women, men, pregnant and lactating women, the elderly, and those at low and moderate baseline zinc status. Urinary zinc excretion responded to zinc status overall and in all subgroups for which there were sufficient data. Hair zinc concentration also responded, but there were insufficient studies for subgroup analysis. Platelet, polymorphonuclear cell, mononuclear cell, and erythrocyte zinc concentration and alkaline phosphatase activity did not appear to be effective biomarkers of zinc status.

CONCLUSIONS

This systematic review confirms that in healthy individuals, plasma, urinary, and hair zinc are reliable biomarkers of zinc status. Further high-quality studies using these biomarkers are required, particularly in infants, adolescents, and immigrant population groups for whom there are limited data. Studies are also required to fully assess a range of additional potential zinc biomarkers.

Indicators of zinc status at the population level: a review of the evidence

The role of zinc deficiency as an important cause of morbidity and impaired linear growth has prompted the need to identify indicators of population zinc status. Three indicators have been recommended - prevalence of zinc intakes below the estimated average requirement (EAR), percentage with low serum zinc concentrations, and percentage of children aged < 5 years who are stunted. This review outlines steps to estimate the prevalence of inadequate intakes, and confirm their validity based on the EARs set by International Zinc Nutrition Collaborative Group. Next, the appropriateness of serum zinc as a biochemical marker for population zinc status is confirmed by a summary of: (a) the response of serum zinc concentrations to zinc intakes; (b) usefulness of serum zinc concentrations to predict functional responses to zinc interventions; (c) relationship between initial serum zinc and change in serum zinc in response to interventions. Height- or length-for-age was chosen as the best functional outcome after considering the responses of growth, infectious diseases (diarrhoea, pneumonia), and developmental outcomes in zinc supplementation trials and correlation studies. The potential of other zinc biomarkers such as zinc concentrations in hair, cells, zinc-metalloenzymes, and zinc-binding proteins, such as metallothionein, is also discussed. Molecular techniques employing reverse transcriptase (RT)-polymerase chain reaction to measure mRNA in metallothionein and ZIP1 transporter hold promise, as do kinetic markers such as exchangeable zinc pools (EZP) and plasma zinc turnover rates. More research is needed to establish the validity, specificity, sensitivity, and feasibility of these new biomarkers, especially in community-settings.

Dietary indicators for assessing the adequacy of population zinc intakes

The assessment of dietary zinc intakes is an important component of evaluating the risk of zinc deficiency in populations, and for designing appropriate food-based interventions, including fortification, to improve zinc intakes. The prevalence of inadequate zinc intakes can describe the relative magnitude of the risk of zinc deficiency in the population and identify subpopulations at elevated risk. As a cornerstone to evaluating the adequacy of population zinc intakes globally, a set of internationally appropriate dietary reference intakes must be defined. The World Health Organization/Food and Agriculture Organization/International Atomic Energy Agency (WHO/FAO/IAEA) and the Food and Nutrition Board/US Institute of Medicine (FNB/IOM) have presented estimated average requirements (EAR) for dietary zinc intake, and, more recently, the International Zinc Nutrition Consultative Group (IZiNCG) presented a revised set of recommendations for international use. A prevalence of inadequate zinc intakes greater than 25% is considered to represent an elevated risk of population zinc deficiency. As the requirement estimates are derived from smaller, clinical studies and, for children, most components of the estimates are extrapolated from data for adults, it was desirable to evaluate their internal validity. The estimated physiological requirements for adult men and women appear to adequately predict zinc status as determined by biochemical indicators of status and/or zinc balance. With the use of data from available studies, the reported prevalence of low serum zinc concentration and the estimated prevalence of inadequate zinc intakes predict similar levels of risk of zinc deficiency, particularly among pregnant and nonpregnant women. Conformity between these two indicators is less consistent for children, suggesting that further data and/or direct studies of zinc requirements among children are needed.

Antioxidant supplementation in sepsis and systemic inflammatory response syndrome

OBJECTIVE

Summarize the current knowledge about oxidative stress-related organ dysfunction in inflammatory and septic conditions, and its potential prevention and treatment by antioxidants in critically ill patients, focusing on naturally occurring antioxidants and clinical trials.

STUDY SELECTION

PubMed, MEDLINE, and personal database search.

SYNTHESIS

Plasma concentrations of antioxidant micronutrients are depressed during critical illness and especially during sepsis. The causes of these low levels include losses with biological fluids, low intakes, dilution by resuscitation fluids, as well as systemic inflammatory response syndrome-mediated redistribution of micronutrients from plasma to tissues. Numerous clinical trials have been conducted, many of which have shown beneficial effects of supplementation. Interestingly, among the candidates, glutamine, glutathione, and selenium are linked with the potent glutathione peroxidase enzyme family at some stage of their synthesis and metabolism.

CONCLUSIONS

Three antioxidant nutrients have demonstrated clinical benefits and reached level A evidence: a) selenium improves clinical outcome (infections, organ failure); b) glutamine reduces infectious complication in large-sized trials; and c) the association of eicosapentaenoic acid and micronutrients has significant anti-inflammatory effects. Other antioxidants are still on the clinical benchmark level, awaiting well-designed clinical trials.

Assessment of intake inadequacy and food sources of zinc of people in China

Objectives

To assess the intake inadequacy and food sources of zinc of people in China.

Design and subjects

Diets of 68 962 subjects aged 2–101 years (urban 21 103, rural 47 859) in the 2002 China National Nutrition and Health Survey were analysed. Dietary intake was assessed using 24-hour recall for three consecutive days. Zinc intake inadequacy was calculated based on values suggested by the World Health Organization.

Results

The median zinc intake ranged from 4.9 mg day− 1(urban girls, 2–3 years) to 11.9 mg day− 1(rural males, 19+ years). The zinc density of urban residents (2–3 to 19+ years) was 5.0–5.3 mg day− 1 (1000 kcal)− 1, significantly higher than that of their rural counterparts (4.7–4.8 mg day− 1 (1000 kcal)− 1). Differences in food sources of zinc from cereal grains (27.4–45.1 vs. 51.6–63.2%) and animal foods (28.4–54.8 vs. 16.8–30.6%) were found between urban and rural residents. Zinc from vegetables and fruits (8.2–13.8 vs. 9.7–12.4%) and legumes (1.3–3.3 vs. 2.5–3.4%) was comparable between urban and rural residents. The proportion of zinc intake inadequacy ranged between 2.8% (urban females, 19+ years) and 29.4% (rural lactating women). Rural residents had higher proportions of zinc intake inadequacy than their urban counterparts. Significantly higher proportions of zinc inadequacy were found in the category of phytate/zinc molar ratio >15 for both rural and urban residents.

Conclusions

About 20% of rural children are at risk of inadequate zinc intake, with phytate as a potential important inhibitor. Moreover, lactating women are also considered a vulnerable group.

Mononuclear cell metallothionein mRNA levels in human subjects with poor zinc nutrition

Human zinc deficiency is thought to be prevalent worldwide, particularly in populations with diets low in zinc and animal protein and high in inhibitors of zinc absorption, such as phytic acid. Confirmation of zinc deficiency is, however, difficult in the absence of a reliable and sensitive marker of zinc status. Under controlled conditions, T-lymphocyte metallothionein-2A (MT-2A) mRNA levels change in relation to zinc status and the objective of the present study was to investigate whether these transcript levels could be related to dietary zinc intake, plasma zinc or other biochemical parameters influenced by, or influencing, zinc metabolism in human subjects likely to be zinc deficient. Rural Koreans (n 110, age 50-80 years) with a range of zinc and phytic acid dietary intake were recruited for the study and blood samples were analysed for plasma zinc, HDL, LDL, alpha-tocopherol and thiobarbituric acid reactive substances, mononuclear cell (MNC) MT-2A mRNA, serum protein and albumin, and blood haematocrit, Hb and glucose. Multiple correlation and principal component analysis showed a significant negative correlation between plasma zinc and MNC MT-2A mRNA levels. Female subjects had higher MT-2A transcript levels than males and MT-2A mRNA levels tended to increase with age. There was no significant association between dietary zinc intake or any index of zinc intake relating to dietary inhibitors of zinc absorption. It is concluded that MNC MT-2A mRNA levels cannot be used to predict poor zinc nutrition.

Dominance of sphingomonads in a copper-exposed biofilm community for groundwater treatment

The structure, biological activity and microbial biodiversity of a biofilm used for the removal of copper from groundwater were studied and compared with those of a biofilm grown under copper-free conditions. A laboratory-scale submerged fixed biofilter was fed with groundwater (2.3 l h(-1)) artificially polluted with Cu(II) (15 mg l(-1)) and amended with sucrose (150 mg l(-1)) as carbon source. Between 73 and 90 % of the Cu(II) was removed from water during long-term operation (over 200 days). The biofilm was a complex ecosystem, consisting of eukaryotic and prokaryotic micro-organisms. Scanning electron microscopy revealed marked structural changes in the biofilm induced by Cu(II), compared to the biofilm grown in absence of the heavy metal. Analysis of cell-bound extracellular polymeric substances (EPS) demonstrated a significant modification of the composition of cell envelopes in response to Cu(II). Transmission electron microscopy and energy-dispersive X-ray microanalysis (EDX) showed that copper bioaccumulated in the EPS matrix by becoming bound to phosphates and/or silicates, whereas copper accumulated only intracytoplasmically in cells of eukaryotic microbes. Cu(II) also decreased sucrose consumption, ATP content and alkaline phosphatase activity of the biofilm. A detailed study of the bacterial community composition was conducted by 16S rRNA-based temperature gradient gel electrophoresis (TGGE) profiling, which showed spatial and temporal stability of the species diversity of copper-exposed biofilms during biofilter operation. PCR reamplification and sequencing of 14 TGGE bands showed the prevalence of alphaproteobacteria, with most sequences (78 %) affiliated to the Sphingomonadaceae. The major cultivable colony type in plate counts of the copper-exposed biofilm was also identified as that of Sphingomonas sp. These data confirm a major role of these organisms in the composition of the Cu(II)-removing community.

Processing of complementary food does not increase hair zinc levels and growth of infants in Kilosa district, rural Tanzania

A community-based, randomized, placebo-controlled, double-blind trial was conducted from March 2001 to March 2002 in Kilosa, a rural district of Morogoro Region in Tanzania. One hundred and fifty-eight infants were selected randomly from lists of local Maternal and Child Health Care Centres and received either processed complementary food (PCF) or unprocessed complementary food (UPCF) from age 6 to 12 months. Processing increased Zn solubility and energy density of the porridge prepared from the complementary food (CF) as determined in vitro. Phytate:Zn molar ratio of the PCF and UPCF was 25·8 and 47·5, respectively. Under the study conditions, the processing of CF did not improve Zn status as measured by hair analysis. No significant correlations were found between hair Zn values and anthropometric measurements. Our findings suggest that processing alone of cereal-based CF may be insufficient to ensure an adequate supply of Zn to improve growth and Zn status of infants. Dietary modification to tackle Zn deficiencies in similar target groups may therefore only be successful when other Zn-rich foods such as meat and fish are included.

Impact of micronutrient dietary intake and status on intestinal zinc absorption in late middle-aged men: the ZENITH study

BACKGROUND

Adjustments in intestinal absorption and losses of zinc (Zn) are thought to maintain Zn homeostasis when dietary intake levels are altered. Zn status may also influence efficiency of intestinal Zn absorption.

OBJECTIVES

To determine the impact of dietary intake and status of some micronutrients on Zn absorption in late middle-aged men.

DESIGN AND PARTICIPANTS

Dietary intake and status of Zn, Cu, Fe, vitamin A, C and fibre, and absorption of Zn were measured in 48 men, aged 58-68 y, confined to a metabolic unit and consuming a typical French diet. Dietary intake was estimated using 4-day food-intake records (including the weekend) and the GENI program. To assess Zn status, serum, erythrocyte, urine Zn levels and serum alkaline phosphatase activity were determined. Zn absorption was determined using the isotope double-labelling method. Zn stable isotopic ratios were measured in plasma samples collected before and 48 h after isotope administration using ICP/MS.

RESULTS

Zn intake within the group of men varied from 5.7 to 20.5 mg/day and averaged 12.9 mg/day. Serum Zn level varied from 10 to 18 micromol/l and averaged 12.9 micromol/l. Zn absorption varied from 12 to 46% and averaged 29.7%. Zn absorption was not significantly (P > 0.05) correlated with Zn intake or with any of the Zn status parameters. Zn absorption was only slightly negatively correlated with serum and erythrocyte Zn levels and with serum Fe and ferritin levels in this study.

CONCLUSION

Zn dietary intake and Zn absorption were satisfactory and led to an adequate Zn status in this population.