Assessment of zinc status in man

Improving growth in infants with CF

Cystic fibrosis (CF) results in chronic pulmonary infections, inflammation, pancreatic insufficiency, and multiple gastrointestinal manifestations. Malnutrition and poor growth are hallmarks of CF, and strongly associated with poor outcomes. Through newborn screening, many infants can be diagnosed within a few days of life, which allows for early initiation of nutritional counseling and close clinical follow-up. Obstacles to growth for infants with CF start in utero, as newborns with CF can have a lower birth weight than the general population. Improving infant growth has been linked to improved clinical outcomes and survival. It remains a top priority and challenge for caregivers and healthcare teams. An interdisciplinary approach, including registered dietitian and social work support, is essential to optimize health for infants with CF. Remaining barriers to normalcy include deficits in linear growth, lack of accurate nutrition biomarkers, persistence of inequities related to social determinant of health, particularly in the global CF community.

Co-expression of multiple heavy metal transporters changes the translocation, accumulation, and potential oxidative stress of Cd and Zn in rice (Oryza sativa)

The OsHMA2, OsLCT1 and OsZIP3 transporters were all involved in zinc (Zn) and cadmium (Cd) transport. So far, only a few researches studied on the co-regulation effect of three transporters related to Zn and Cd transport. The present study showed that rice co-expressing OsLCT1-OsHMA2-OsZIP3 (LHZ) had longer roots and shoots than wild-type (WT) rice after Zn and Cd treatments. The chlorophyll content was significantly higher, and the proline, malondialdehyde and H₂O₂ contents were significantly lower in co-transgenic lines than in WT under Cd and Zn stress. LHZ in the seedlings of transgenic rice decreased the root-to-shoot translocation of Cd after Cd and Zn treatments. At the filling stage, LHZ line reduced Cd accumulation in grain after Cd treatment. Moreover, LHZ line increased the translocation of Zn to grain and reduced the accumulation of Cd after Zn treatment. These results suggested that LHZ co-expression could effectively decrease the translocation and accumulation of Cd to grains, alleviated the oxidative stress of Cd and Zn, and finally enhanced the quality and safety of rice grains.

Zinc supplementation enhances linear growth in school-aged children: A randomized controlled trial

Zinc supplementation in children in endemic area of zinc deficiency had been reported of growth enhancement; however, the results were inconsistence. This study aimed to evaluate the efficacy of zinc supplementation on growth of school-aged children. A randomized double-blinded controlled trial was conducted in 140 Thai school children. Placebo or zinc bisglycinate (15 mg element zinc) were taken on school day for 6 months. Pre- and posttreatment anthropometric parameters were recorded. Changes in height from the baseline was considered as the primary outcome whereas, changes in other anthropometric parameters were considered as the secondary outcomes. The mean age was 8.9 years; baseline anthropometric data were not significant different between groups. At the end of study, children in zinc group had significantly higher gain in height (5.6±2.4 vs 4.7±1.4 cm, respectively; P=0.009) and height Z-score (0.45±0.37 vs 0.37±0.27, respectively; P=0.048) than children in control group. No significant differences of other anthropometric parameters were observed. In conclusion, zinc supplementation increased linear growth in Thai schoolaged children over a 6-month period but it had no effects on other anthropometric parameters.

Effect of zinc plus multivitamin supplementation on growth in school children

BACKGROUND

Zinc and multiple vitamins are essential for growth. Zinc and vitamin deficiency is very common in developing countries. The aim of this study was to assess the efficacy of zinc plus multivitamin supplements in improving growth of healthy Thai schoolchildren.

METHODS

A randomized controlled trial was conducted in healthy 4-13-year-old Thai schoolchildren attending public school in central Thailand. Participants were randomized to receive either chelated zinc in the form of zinc bis-glycinate (20 mg elemental zinc) plus multivitamins (vitamin A, 1000 IU; vitamin D, 200 IU; B1, 10 mg; B2, 3 mg; B6, 1 mg; B12, 10 μg; nicotinamide, 40 mg) or placebo once per day, 5 days per week for 6 months. Primary outcome was change in height from baseline to the end of the study. Secondary outcomes were change in weight, body mass index, waist and hip circumferences and waist-to-height ratio. An intention-to-treat analysis was performed.

RESULTS

Seventy children each were randomized to the treatment and placebo groups. The children who received zinc and multivitamins had significantly higher gain in height (4.9 ± 1.3 vs 3.6 ± 0.9 cm, respectively; P < 0.001). Subgroup analysis showed significant improvement in height, especially in preadolescents. The increased gain in height was irrespective of baseline height and weight. The extra gain in height occurred after 2 months of supplementation. The changes in other anthropometric indices were not significantly different.

CONCLUSION

Supplementation of chelated zinc plus multivitamins for 6 months significantly increased height gain in Thai schoolchildren and was well tolerated.

Effect of zinc intake on serum/plasma zinc status in infants: a meta-analysis

A systematic review and meta-analysis of available randomised controlled trials (RCTs) was conducted to evaluate the effect of zinc (Zn) intake on serum/plasma Zn status in infants. Out of 5500 studies identified through electronic searches and reference lists, 13 RCTs were selected after applying the exclusion/inclusion criteria. The influence of Zn intake on serum/plasma Zn concentration was considered in the overall meta-analysis. Other variables were also taken into account as possible effect modifiers: doses of Zn intake, intervention duration, nutritional status and risk of bias. The pooled β of status was 0.09 [confidence interval (CI) 0.05 to 0.12]. However, a substantial heterogeneity was present in the analyses (I(2) = 98%; P = 0.00001). When we performed a meta-regression, the effect of Zn intake on serum/plasma Zn status changed depending on the duration of the intervention, the dose of supplementation and the nutritional situation (P ANCOVA = 0.054; <0.001 and <0.007, respectively). After stratifying the sample according to the effect modifiers, the results by duration of intervention showed a positive effect when Zn intake was provided during medium and long periods of time (4-20 weeks and >20 weeks). A positive effect was also seen when doses ranged from 8.1 to 12 mg day(-1). In all cases, the pooled β showed high evidence of heterogeneity. Zn supplementation increases serum/plasma Zn status in infants, although high evidence of heterogeneity was found. Further standardised research is urgently needed to reach evidence-based conclusions to clarify the role of Zn supplementation upon infant serum/plasma Zn status, particularly in Europe.

Operational feasibility of implementing community-based zinc supplementation: impact on childhood diarrheal morbidity

OBJECTIVE

To determine the effect of zinc supplementation on diarrheal incidence and to discover any operational constraints of zinc supplementation at the community level.

METHODS

We included 1712 children aged between 6 and 48 months in a randomized double blind study in rural area comprising of 11 villages. Children were randomly divided into 2 groups. Zinc/placebo syrup supplementation was continued for 6 months in a weekly schedule from May 2003. Children were followed up weekly for detection of diarrhea from May 2003 until April 2004. Around 30% of the study children were evaluated every 2 months during supplementation period.

RESULTS

During the period, 80,534 weekly visits were made giving 1548.73-child years of observation. We detected 1438 diarrheal episodes among 846 children. The incidence of diarrhea was significantly less during the supplemented period (P < 0.001; RR 0.74 (0.64-0.87)) in the zinc group. A significant difference was also noted during the follow up period (P < 0.05). In the zinc group, children <2 years of age had significantly less diarrhea during supplementation and the follow up period. Multiple episodes of diarrhea (>or=2) were significantly less in the zinc group. Approximately 85% of the surveillance workers made weekly visits to the houses and 96% of mothers administered syrup weekly to their children. Around 80% of mother's were aware of the possible benefits of zinc supplementation.

CONCLUSION

Weekly zinc supplementation was effective in reducing diarrheal morbidity at the community level and it was operationally feasible.

Treatment of infectious diarrhea in children

Diarrheal diseases remain an important cause of childhood morbidity and death in developing countries, although diarrheal deaths have significantly declined in recent years, mostly due to successes in the implementation of oral rehydration therapy (ORT), which is the principal treatment modality. Diarrhea may occur for varied reasons; however, most episodes of diarrhea in developing countries are infectious in origin. Three clinical forms of diarrhea (acute watery diarrhea, invasive diarrhea, and persistent diarrhea) have been identified to formulate a management plan. Acute diarrhea may be watery (where features of dehydration are prominent) or dysenteric (where stools contain blood and mucus). Rehydration therapy is the key to management of acute watery diarrhea, whereas antimicrobial agents play a vital role in the management of acute invasive diarrhea, particularly shigellosis and amebiasis. In persistent diarrhea, nutritional therapy, including dietary manipulations, is a very important aspect in its management, in addition to rehydration therapy. Rehydration may be carried out either by the oral or intravenous route, depending upon the degree of dehydration. Oral rehydration salts (ORS) solution (World Health Organization formula) is recommended for ORT. Intravenous fluid is recommended for initial management of severe dehydration due to diarrhea, followed by ORT with ORS solution for correction of ongoing fluid losses. Antimicrobial therapy is beneficial for cholera and shigellosis. Antiparasitic agents are indicated only if amebiasis and giardiasis are present. Appropriate feeding during diarrhea is recommended for nutritional recovery and to prevent bodyweight loss. Antidiarrheal agents do not provide additional benefit in the management of infectious diarrhea. Although some probiotics have been shown to be beneficial in the treatment of acute diarrhea due to rotavirus, their use in the treatment of diarrhea is yet to be recommended, even in developed countries. The children of developing countries might benefit from zinc supplementation during the diarrheal illness, but its mode of delivery and cost effectiveness are yet to be decided.

Assessing micronutrient status in the presence of inflammation

Measurement of micronutrient status in the presence of inflammation is difficult for several reasons. Changes in levels of acute phase proteins are associated with increased plasma levels of some indicators of micronutrient status, such as ferritin, and decrease of others, such as retinol. Alterations in the plasma levels of acute phase proteins can occur from hemodilution, sequestration and increased or decreased rates of synthesis and breakdown. How much these relate to functional deficiency is not known. Assays that are less perturbed by inflammation, such as the transferrin receptor assay, and adjustment of plasma micronutrient levels according to different cutoff levels for acute phase proteins are helpful but they do not enable precise assessment of micronutrient status among individuals who are infected. Improving assessment of micronutrient status is important if micronutrient interventions are to be targeted to those with the greatest need.

Zinc homeostasis in Malawian children consuming a high-phytate, maize-based diet

BACKGROUND

Zinc deficiency in children is an important public health concern in the developing world, and the consumption of predominantly cereal-based diets with a high phytate content may contribute to the risk. The gastrointestinal tract plays a central role in absorbing and conserving zinc, yet it has not been carefully studied in such children.

OBJECTIVE

This study investigated zinc homeostasis in healthy, free-living Malawian children with habitually high-phytate diets to better understand the role of the gastrointestinal tract.

DESIGN

We evaluated zinc homeostasis in 10 children aged 2-5 y who were consuming a maize-based diet (phytate:zinc molar ratio of 23:1). Zinc stable isotopes were administered orally and intravenously. The tracer and tracee were measured in urine and feces.

RESULTS

Endogenous fecal zinc was high in comparison with results for this measure in previous studies. Typical correlations seen in subjects consuming a low-phytate diet between total absorbed zinc, the size of the exchangeable zinc pool, and endogenous fecal zinc were not observed. Fractional absorption of zinc was 0.24.

CONCLUSIONS

Zinc homeostasis was perturbed, particularly by large, endogenous fecal zinc losses, in this vulnerable population. The effects of interventions to improve zinc status, including dietary phytate reduction, on zinc homeostasis merit further study.

Effect of supplemental zinc on the growth and serum zinc concentrations of prepubertal children: a meta-analysis of randomized controlled trials

BACKGROUND

Multiple studies have been carried out to assess the effect of zinc supplementation on children's growth. The results of these studies are inconsistent, and the factors responsible for these varied outcomes are unknown.

OBJECTIVE

Meta-analyses of randomized controlled intervention trials were therefore completed to assess the effect of zinc supplementation on the physical growth and serum zinc concentrations of prepubertal children.

DESIGN

A total of 33 acceptable studies with appropriate data were identified by MEDLINE (National Library of Medicine, Bethesda, MD) searches and other methods. Weighted mean effect sizes (expressed in SD units) were calculated for changes in height, weight, weight-for-height, and serum zinc concentration by using random-effects models; factors associated with effect sizes were explored by meta-regression techniques.

RESULTS

Zinc supplementation produced highly significant, positive responses in height and weight increments, with effect sizes of 0.350 (95% CI: 0.189, 0.511) and 0.309 (0.178, 0.439), respectively. There was no significant effect of zinc on weight-for-height indexes [weighted mean effect size: -0.018 (-0.132, 0.097)]. Zinc supplementation caused a large increase in the children's serum zinc concentrations, with an effect size of 0.820 (0.499, 1.14). Growth responses were greater in children with low initial weight-for-age z scores and in those aged >6 mo with low initial height-for-age z scores.

CONCLUSIONS

Interventions to improve children's zinc nutriture should be considered in populations at risk of zinc deficiency, especially where there are elevated rates of underweight or stunting. The population mean serum zinc concentration is a useful indicator of the successful delivery and absorption of zinc supplements in children.

Interrelationships of key variables of human zinc homeostasis: relevance to dietary zinc requirements

Currently, estimates of human zinc requirements depend primarily on a factorial approach. The availability of tracer techniques employing zinc stable isotopes has facilitated the acquisition of data on major variables of zinc homeostasis in addition to those that can be measured with careful metabolic balance techniques. These data have promising potential to facilitate and improve the factorial approach. The thesis proposed in this paper is that realistic estimations of dietary zinc requirements by a factorial approach require attention to the dynamic interrelationships between major variables of zinc homeostasis. This applies especially to the positive relationship between endogenous fecal zinc and total absorbed zinc, which is the essential starting point in estimating physiologic and, from there, dietary requirements.

Vitamin and mineral nutrition for the health and development of the children of Europe

Most European countries are now affected by demographic transition and changing epidemiology of disease; the nutrition of children is increasingly recognised as crucial for present and future health. Adequate dietary intake and nutritional status among children are important for their own growth, development and function but there is now increasing evidence that childhood nutrition also influences adult health. Intrauterine nutrition influences adult morbidity and mortality, but the childhood diet and nutritional status modify the increased risk of being born small. Thus, childhood diet needs to be taken more seriously in order to improve a nation's health as well as producing bright, active children. A key factor is the recognition that nutritional interventions at different stages of the life cycle are necessary if childhood nutrition is to improve. The mosaic pattern of the geography and social structure of communities in Europe produces ‘poverty’ and ‘consumer’ related nutrition patterns - often side by side. At one extreme, there is an urgent need to prevent obesity; while at the other extreme serious attention is required towards the prevention of deficiency disorders, mostly related to poverty and social exclusion. Few European governments take childhood nutrition at all seriously. This paper reviews a number of micronutrient issues and makes the case for the development of evidence-based policies and programmes for improving the nutrition of children in Europe.

Abnormalities in zinc homeostasis in young infants with cystic fibrosis

Low plasma zinc concentrations have been reported in approximately 30% of young infants with cystic fibrosis identified by newborn screening. The objective of this study was to examine zinc homeostasis in this population by application of stable isotope methodology. Fifteen infants with cystic fibrosis (9 male, 6 female; 7 breast-fed, 8 formula-fed) were studied at a mean (+/-SD) age of 1.8 +/- 0.7 mo. On d 1, 70Zn was administered intravenously, and 67Zn was quantitatively administered with all human milk/formula feeds during the day. Three days later, a 3-d metabolic period was initiated, during which time intake was measured and complete urine and fecal collections were obtained. Fractional zinc absorption, total absorbed zinc, endogenous fecal zinc, and net absorbed zinc were measured; fecal fat excretion was also determined. Fractional absorption was significantly higher for the breast-fed infants (0.40 +/- 0.21) compared with the formula-fed group (0.13 +/- 0.06) (p = 0.01), but with the significantly higher dietary zinc intake of the formula-fed group, total absorbed zinc was higher for those receiving formula (p = 0.01). In 1 infants with complete zinc metabolic data, excretion of endogenous zinc was twofold greater for the formula-fed infants (p < 0.05); net absorption (mg zinc/d) was negative for both feeding groups: -0.04 +/- 0.52 for breast-fed; -0.28 +/- 0.57 for formula-fed. Endogenous fecal zinc losses correlated with fecal fat excretion (r = 0.89, n = 9, p = 0.001), suggesting interference with normal conservation of endogenously secreted zinc. These findings indicate impaired zinc homeostasis in this population and suggest an explanation for the observations of suboptimal zinc status in many young infants with cystic fibrosis prior to diagnosis and treatment.

Human zinc deficiency

The objective of this paper is to provide a current overview of the significance of zinc in human nutrition. To achieve this, the following issues are addressed: (1) the biochemistry and biology of zinc in the context of their relevance to zinc in human nutrition and to our understanding of the complexity and practical importance of human zinc deficiency; (2) the history of our understanding of human zinc deficiency with an emphasis both on its brevity and on notable recent progress; (3) the clinical spectrum of severe zinc deficiency; (4) the lack of ideal biomarkers for milder zinc deficiency states, with the consequent dependence on randomized, placebo-controlled intervention studies to ascertain their prevalence and clinical consequences, including growth delay, diarrhea, pneumonia, other infections, disturbed neuropsychological performance and abnormalities of fetal development; (5) the public health significance of human zinc deficiency in the developing world; (6) reasons for concern and unanswered questions about zinc nutriture in the United States; (7) the need for better understanding of human zinc metabolism and homeostasis (including its limitations) at a molecular, cellular, organ-system and whole body level and of factors that affect zinc bioavailability; and (8) potential strategies for the prevention and management of human zinc deficiency. This review concludes with an emphasis on the immediate need for expanded research in directions that have become increasingly well demarcated and impelling as a result of recent progress, which is summarized in this overview.

Low plasma zinc concentrations in young infants with cystic fibrosis

OBJECTIVES

The purpose of this study was to examine the zinc status of young infants with cystic fibrosis before and after the initiation of pancreatic enzyme therapy.

STUDY DESIGN

Cross-sectional data were obtained for infants with cystic fibrosis identified by newborn screening. Plasma zinc concentrations were measured and analyzed according to enzyme use at the time of the blood draw. On a subgroup of infants, zinc concentrations were determined again after several weeks with enzyme therapy.

RESULTS

Mean (+/-SD) plasma zinc concentration for the infants studied before the initiation of enzyme therapy was 10.4 +/- 2.2 micromol/L (68.3 +/- 14.7 microgram/dL) (n = 48), which was significantly lower than the mean for those receiving enzymes for >/=2 weeks, 11.8 +/- 2. 3 micromol/L (77.1 +/- 14.9 microgram/dL) (n = 15) (P =.03). For the group not yet receiving enzymes, 29% of infants had zinc concentrations in the deficient range. Data were available before and after enzyme therapy for 30 infants and indicated a mean increase of 1.64 +/- 3.0 micromol/L (10.7 +/- 19.3 microgram/dL) (P =. 005).

CONCLUSIONS

These data suggest that many of the infants were zinc deficient at the time of diagnosis. We conclude that zinc should be included among the specific micronutrients given consideration in the management of cystic fibrosis, particularly in infants.