Zinc supplementation does not alter sensitive biomarkers of copper status in healthy boys

Methods of Assessment of Zinc Status in Humans: An Updated Review and Meta-analysis

CONTEXT

The assessment of zinc status is difficult but essential for the identification of zinc deficiency and evaluation of interventions to improve zinc status.

OBJECTIVE

The purpose of this systematic review (SR) and meta-analysis was to update the previously published SR of biomarkers of zinc status, conducted by the European Micronutrient Recommendations Aligned (EURRECA) network in 2009, to answer the question: Which putative measures (biomarkers) of zinc status appropriately reflect a change in zinc intake of at least 2 weeks?

DATA SOURCES

A structured search strategy was used to identify articles published between January 2007 and September 2022 from MEDLINE (Ovid), Embase (Ovid), Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials (CENTRAL). Relevant articles were identified using previously defined eligibility criteria.

DATA EXTRACTION

Data were extracted and combined with data from the previous SR.

DATA ANALYSIS

A random-effects model was used to calculate pooled mean differences using STATA (StataCorp). The risk of bias and the certainty of evidence for all outcomes were assessed. Additional data on 7 of the 32 previously reported biomarkers were identified, along with data on an additional 40 putative biomarkers from studies published since 2007. Pooled data analysis confirmed that, in healthy participants, both plasma/serum zinc concentration and urinary zinc excretion responded to changes in zinc intake (plasma/serum: mean effect [95% CI], controlled studies: 2.17 µmol/L [1.73, 2.61]; P < .005, I2 = 97.8; before-and-after studies: 2.87 µmol/L [2.45, 3.30]; P < .005, I2 = 98.1%; urine zinc: 0.39 mmol/mol creatinine [0.17, 0.62]; P < .005, I2 = 81.2; 3.09 µmol/day [0.16, 6.02]; P = .039, I2 = 94.3).

CONCLUSION

The updated analyses support the conclusion that plasma/serum and urinary zinc respond to changes in zinc intake in studies of healthy participants. Several additional putative biomarkers were identified, but more studies are needed to assess the sensitivity and reliability.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO no. CRD42020219843.

Zinc supplementation for preventing mortality, morbidity, and growth failure in children aged 6 months to 12 years

BACKGROUND

Zinc deficiency is prevalent in low- and middle-income countries, and is considered a significant risk factor for morbidity, mortality, and linear growth failure. The effectiveness of preventive zinc supplementation in reducing prevalence of zinc deficiency needs to be assessed.

OBJECTIVES

To assess the effects of zinc supplementation for preventing mortality and morbidity, and for promoting growth, in children aged 6 months to 12 years.

SEARCH METHODS

A previous version of this review was published in 2014. In this update, we searched CENTRAL, MEDLINE, Embase, five other databases, and one trials register up to February 2022, together with reference checking and contact with study authors to identify additional studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of preventive zinc supplementation in children aged 6 months to 12 years compared with no intervention, a placebo, or a waiting list control. We excluded hospitalized children and children with chronic diseases or conditions. We excluded food fortification or intake, sprinkles, and therapeutic interventions.

DATA COLLECTION AND ANALYSIS

Two review authors screened studies, extracted data, and assessed the risk of bias. We contacted study authors for missing information and used GRADE to assess the certainty of evidence. The primary outcomes of this review were all-cause mortality; and cause-specific mortality, due to all-cause diarrhea, lower respiratory tract infection (LRTI, including pneumonia), and malaria. We also collected information on a number of secondary outcomes, such as those related to diarrhea and LRTI morbidity, growth outcomes and serum levels of micronutrients, and adverse events.

MAIN RESULTS

We included 16 new studies in this review, resulting in a total of 96 RCTs with 219,584 eligible participants. The included studies were conducted in 34 countries; 87 of them in low- or middle-income countries. Most of the children included in this review were under five years of age. The intervention was delivered most commonly in the form of syrup as zinc sulfate, and the most common dose was between 10 mg and 15 mg daily. The median duration of follow-up was 26 weeks. We did not consider that the evidence for the key analyses of morbidity and mortality outcomes was affected by risk of bias. High-certainty evidence showed little to no difference in all-cause mortality with preventive zinc supplementation compared to no zinc (risk ratio (RR) 0.93, 95% confidence interval (CI) 0.84 to 1.03; 16 studies, 17 comparisons, 143,474 participants). Moderate-certainty evidence showed that preventive zinc supplementation compared to no zinc likely results in little to no difference in mortality due to all-cause diarrhea (RR 0.95, 95% CI 0.69 to 1.31; 4 studies, 132,321 participants); but probably reduces mortality due to LRTI (RR 0.86, 95% CI 0.64 to 1.15; 3 studies, 132,063 participants) and mortality due to malaria (RR 0.90, 95% CI 0.77 to 1.06; 2 studies, 42,818 participants); however, the confidence intervals around the summary estimates for these outcomes were wide, and we could not rule out a possibility of increased risk of mortality. Preventive zinc supplementation likely reduces the incidence of all-cause diarrhea (RR 0.91, 95% CI 0.90 to 0.93; 39 studies, 19,468 participants; moderate-certainty evidence) but results in little to no difference in morbidity due to LRTI (RR 1.01, 95% CI 0.95 to 1.08; 19 studies, 10,555 participants; high-certainty evidence) compared to no zinc. There was moderate-certainty evidence that preventive zinc supplementation likely leads to a slight increase in height (standardized mean difference (SMD) 0.12, 95% CI 0.09 to 0.14; 74 studies, 20,720 participants). Zinc supplementation was associated with an increase in the number of participants with at least one vomiting episode (RR 1.29, 95% CI 1.14 to 1.46; 5 studies, 35,192 participants; high-certainty evidence). We report a number of other outcomes, including the effect of zinc supplementation on weight and serum markers such as zinc, hemoglobin, iron, copper, etc. We also performed a number of subgroup analyses and there was a consistent finding for a number of outcomes that co-supplementation of zinc with iron decreased the beneficial effect of zinc.

AUTHORS' CONCLUSIONS

Even though we included 16 new studies in this update, the overall conclusions of the review remain unchanged. Zinc supplementation might help prevent episodes of diarrhea and improve growth slightly, particularly in children aged 6 months to 12 years of age. The benefits of preventive zinc supplementation may outweigh the harms in regions where the risk of zinc deficiency is relatively high.

Reconsidering the Tolerable Upper Levels of Zinc Intake among Infants and Young Children: A Systematic Review of the Available Evidence

Safe upper levels (UL) of zinc intake for children were established based on either (1) limited data from just one study among children or (2) extrapolations from studies in adults. Resulting ULs are less than amounts of zinc consumed by children in many studies that reported benefits of zinc interventions, and usual dietary zinc intakes often exceed the UL, with no apparent adverse effects. Therefore, existing ULs may be too low. We conducted a systematic bibliographic review of studies among preadolescent children, in which (1) additional zinc was provided vs. no additional zinc provided, and (2) the effect of zinc on serum or plasma copper, ceruloplasmin, ferritin, transferrin receptor, lipids, or hemoglobin or erythrocyte super-oxide dismutase were assessed. We extracted data from 44 relevant studies with 141 comparisons. Meta-analyses found no significant overall effect of providing additional zinc, except for a significant negative effect on ferritin (p = 0.001), albeit not consistent in relation to the zinc dose. Interpretation is complicated by the significant heterogeneity of results and uncertainties regarding the physiological and clinical significance of outcomes. Current zinc ULs should be reassessed and potentially revised using data now available for preadolescent children and considering challenges regarding interpretation of results.

Seasonal Dynamics of Copper Deficiency in Wumeng Semi-Fine Wool Sheep

A study of the seasonal dynamics of copper (Cu) deficiency and its effects on the antioxidant system in Wumeng semi-fine wool sheep in Weining county was conducted. In addition, the concentrations of mineral elements in soil, grass, and blood of affected and healthy Wumeng semi-fine wool sheep were determined, and blood indices were measured. The results showed that Cu contents in soil, grass, and sheep blood from the experimental pasture were significantly lower than those from the control pasture (P < 0.05), while the Mo content in the samples from the experimental pasture were higher than those from the control pasture (P < 0.05). Hb, RBC, PCV, and MDA values in the blood of affected sheep were significantly higher than those of healthy sheep, the content of TP was significantly lower (P < 0.05), and the activities of CAT, GSH-Px, CP, SOD, POD, and TP in the blood of affected sheep were lower than those in healthy sheep (P < 0.05). A comparison of different months showed that the Cu content in soil was higher in November than in June and September. Hb, RBC, PCV, WBC, and the content of MDA in the blood of affected sheep was higher in November than in June and September; however, the change in CP, CAT, GSH-Px, POD, and TP showed the opposite trend. The content of Cu and Mo in soil, grass, and blood showed seasonal changes. Therefore, it is concluded that the seasonal dynamics of Cu deficiency in Wumeng semi-fine wool sheep in Weining was due to the content of Mo and Cu in soil and grass in different seasons, and high Mo concentration in grass affected Cu deficiency in sheep. The function of the antioxidant system of Wumeng semi-fine wool sheep was reduced as a result.

Weighing the risks of high intakes of selected micronutrients compared with the risks of deficiencies

Several intervention strategies are available to reduce micronutrient deficiencies, but uncoordinated implementation of multiple interventions may result in excessive intakes. We reviewed relevant data collection instruments and available information on excessive intakes for selected micronutrients and considered possible approaches for weighing competing risks of intake above tolerable upper intake levels (ULs) versus insufficient intakes at the population level. In general, population-based surveys in low- and middle-income countries suggest that dietary intakes greater than the UL are uncommon, but simulations indicate that fortification and supplementation programs could lead to high intakes under certain scenarios. The risk of excessive intakes can be reduced by considering baseline information on dietary intakes and voluntary supplement use and continuously monitoring program coverage. We describe a framework for comparing risks of micronutrient deficiency and excess, recognizing that critical information for judging these risks is often unavailable. We recommend (1) assessing total dietary intakes and nutritional status; (2) incorporating rapid screening tools for routine monitoring and surveillance; (3) addressing critical research needs, including evaluations of the current ULs, improving biomarkers of excess, and developing methods for predicting and comparing risks and benefits; and (4) ensuring that relevant information is used in decision-making processes.

Excess micronutrient intake: defining toxic effects and upper limits in vulnerable populations

Excessive micronutrient intake causes a variety of adverse health effects, depending on dose and duration. The risk of excess intake carries significant implications for micronutrient delivery interventions, particularly when such programs are overlapping. To minimize risk and provide public health guidance, several countries and the Food and Agriculture Organization of the United Nations/World Health Organization have set upper intake levels (ULs) for various life-stage populations using the risk assessment framework. However, there is a lack of international consensus on the actual ULs due to variability in application of this framework and a scarcity of evidence from which to draw upon, especially for children. Often ULs for children are established through a downward weight-based extrapolation from adult ULs, which is not always appropriate. The published ULs of nine organizations are compared, recent population nutrient intake evidence is presented, and the toxic effects of key minerals and vitamins are reviewed. Finally, the evidence for toxicity and setting of ULs for each nutrient is discussed including a comment on our degree of confidence in the strength of existing individual ULs. Challenges with risk assessment and opportunities for strengthening the definition of ULs are discussed.

Reporting of sex and gender in randomized controlled trials in Canada: a cross-sectional methods study

BACKGROUND

Accurate reporting on sex and gender in health research is integral to ensuring that health interventions are safe and effective. In Canada and internationally, governments, research organizations, journal editors, and health agencies have called for more inclusive research, provision of sex-disaggregated data, and the integration of sex and gender analysis throughout the research process. Sex and gender analysis is generally defined as an approach for considering how and why different subpopulations (e.g., of diverse genders, ages, and social locations) may experience health conditions and interventions in different or similar ways.The objective of this study was to assess the extent and nature of reporting about sex and/or gender, including whether sex and gender analysis (SGA) was carried out in a sample of Canadian randomized controlled trials (RCTs) with human participants.

METHODS

We searched MEDLINE from 01 January 2013 to 23 July 2014 using a validated filter for identification of RCTs, combined with terms related to Canada. Two reviewers screened the search results to identify the first 100 RCTs that were either identified in the trial publication as funded by a Canadian organization or which had a first or last author based in Canada. Data were independently extracted by two people from 10% of the RCTs during an initial training period; once agreement was reached on this sample, the remainder of the data extraction was completed by one person and verified by a second.

RESULTS

The search yielded 1433 records. We screened 256 records to identify 100 RCTs which met our eligibility criteria. The median sample size of the RCTs was 107 participants (range 12-6085). While 98% of studies described the demographic composition of their participants by sex, only 6% conducted a subgroup analysis across sex and 4% reported sex-disaggregated data. No article defined "sex" and/or "gender." No publication carried out a comprehensive sex and gender analysis.

CONCLUSIONS

Findings highlight poor uptake of sex and gender considerations in the Canadian RCT context and underscore the need for better articulated guidance on sex and gender analysis to improve reporting of evidence, inform policy development, and guide future research.

Interactions of cisplatin and the copper transporter CTR1 in human colon cancer cells

There is much interest in understanding the mechanisms by which platinum-based anticancer agents enter cells, and the copper transporter CTR1 has been the focus of many recent studies. While there is a clinical correlation between CTR1 levels and platinum efficacy, cellular studies have provided conflicting evidence relating to the relationship between cisplatin and CTR1. We report here our studies of the relationship between cisplatin and copper homeostasis in human colon cancer cells. While the accumulation of copper and platinum do not appear to compete with each other, we did observe that cisplatin perturbs CTR1 distribution within 10 min, a far shorter incubation time than commonly employed in cellular studies of cisplatin. Furthermore, on these short time-scales, cisplatin caused an increase in the cytoplasmic labile copper pool. While the predominant focus of studies to date has been on CTR1, these studies highlight the importance of investigating the interaction of cisplatin with other copper proteins.

Simulated effects of home fortification of complementary foods with micronutrient powders on risk of inadequate and excessive intakes in West Gojjam, Ethiopia

Home fortification of complementary foods (CFs) with multiple micronutrient powders (MNPs) is being scaled up in various countries, but little is known about the prevailing complementary feeding practices and the type and nutrient gaps to be filled with MNPs. The present study evaluated the complementary feeding practices of young children and simulated the risk of inadequate and excessive intakes associated with home fortification with MNPs. We have assessed the sociodemographic status, anthropometry, and complementary feeding practices of young children (N = 122) in Mecha district, rural Ethiopia. Using a 2-day, quantitative 24-hr recall, usual intakes of energy, protein, iron, zinc, and calcium were estimated. The risks of inadequate and excessive iron and zinc intakes with or without home fortification scenarios were assessed. The simulations considered intakes from CFs assuming average breast milk contributions and additional nutrients provided by the MNPs. Stunting was highly prevalent (50%) and was associated with a lower dietary diversity (P = .009) and nutrient intakes from the CFs. Median energy, zinc, and calcium intakes were below the estimated needs from CFs; protein needs were met. Median dietary iron intake appeared adequate, but 76%, 95% CI [68%, 84%], of children had inadequate intake (assuming low bioavailability), whereas another 8%, 95% CI: [3%, 13%], had excessive intakes. Simulation of daily and alternative day's fortification with MNP decreased the prevalence of inadequate iron and zinc intake but significantly increased the risk of excessive intakes that remained unacceptably high for iron (>2.5%). Untargeted MNP interventions may lead to excessive intakes, even in settings where poor complementary feeding practices are prevalent.

Usual Intake of Key Minerals among Children in the Second Year of Life, NHANES 2003-2012

Iron, calcium, and zinc are important nutrients for the young, developing child. This study describes the usual intake of iron, calcium, and zinc among US children in the second year of life using two days of dietary intake data from the National Health and Nutrition Examination Survey 2003-2012. Estimates were calculated using PC-SIDE to account for within and between person variation. Mean usual iron, calcium, and zinc intakes were 9.5 mg/day, 1046 mg/day, and 7.1 mg/day, respectively. Over a quarter of children had usual iron intakes less than the Recommended Dietary Allowance (RDA) (26.1%). Eleven percent of children had usual calcium intakes below the RDA and over half of children had usual intakes of zinc that exceeded the tolerable upper intake level (UL). Two percent or less had usual intakes below the Estimated Average Requirement (EAR) for iron, calcium, and zinc. Our findings suggest that during 2003-2012, one in four children and one in ten children had usual intakes below the RDA for iron and calcium, respectively. Children who are not meeting their nutrient requirements could be at increased risk for developing deficiencies such as iron deficiency or could lead to a shortage in adequate nutrients required for growth and development. One in every two children is exceeding the UL for zinc, but the interpretation of these estimates should be done with caution given the limited data on adverse health outcomes. Continued monitoring of zinc intake and further assessment for the potential of adverse health outcomes associated with high zinc intakes may be needed.

A Review of Dietary Zinc Recommendations

BACKGROUND

Large discrepancies exist among the dietary zinc recommendations set by expert groups.

OBJECTIVE

To describe the basis for the differences in the dietary zinc recommendations set by the World Health Organization, the US Institute of Medicine, the International Zinc Nutrition Consultative Group, and the European Food Safety Agency.

METHODS

We compared the sources of the data, the concepts, and methods used by the 4 expert groups to set the physiological requirements for absorbed zinc, the dietary zinc requirements (termed estimated and/or average requirements), recommended dietary allowances (or recommended nutrient intakes or population reference intakes), and tolerable upper intake levels for selected age, sex, and life-stage groups.

RESULTS

All 4 expert groups used the factorial approach to estimate the physiological requirements for zinc. These are based on the estimates of absorbed zinc required to offset all obligatory zinc losses plus any additional requirements for absorbed zinc for growth, pregnancy, or lactation. However, discrepancies exist in the reference body weights used, studies selected, approaches to estimate endogenous fecal zinc (EFZ) losses, the adjustments applied to derive dietary zinc requirements that take into account zinc bioavailability in the habitual diets, number of dietary zinc recommendations set, and the nomenclature used to describe them.

CONCLUSIONS

Estimates for the physiological and dietary requirements varied across the 4 expert groups. The European Food Safety Agency was the only expert group that set dietary zinc recommendations at 4 different levels of dietary phytate for adults (but not for children) and as of yet no tolerable upper intake level for any life-stage group.

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.

Zinc supplement use and contribution to zinc intake in Australian children

Objective

The aims of the present study were to examine the Zn intake and characteristics of Zn supplement users and non-users and to survey Zn supplements that are commercially available.

Design

Cross-sectional national nutrition survey (2007 Australian Children’s Nutrition and Physical Activity Survey) and a review of commercially available Zn supplements.

Setting

Australia.

Subjects

Children (n4834) aged 2–16 years.

Results

Zn supplement use was associated with younger age, being female, having a lower BMI and consuming a vegetarian or modified diet. Supplement users had significantly higher intakes of Zn than non-users in all age and gender subgroups. Adolescent boys aged 14–16 years who did not use Zn supplements were at highest risk of inadequate Zn intake (15 % compared with 1 % of users). Conversely, children aged 2–3 years were at highest risk of exceeding the recommended upper limit of Zn intake (86–87 % of users and 64–71 % of non-users), followed by children aged 4–8 years (9–29 % of users and 3–12 % of non-users). The most common sources of Zn supplements consumed by children were multi-vitamin and mineral preparations (92 %), followed by Zn-only supplements (5 %) and Zn-containing cold and flu, or cold sore supplements (3 %). A survey of commercially available Zn supplements revealed that the median elemental Zn content was 2 and 25 mg for multi-vitamin and mineral preparations and Zn-only supplements, respectively.

Conclusions

Based on these data, widespread Zn supplement use among young children is unlikely to be warranted. The impact of exceeding the upper limit of Zn intake on biomarkers of Zn toxicity requires further investigation.

Differences in energy and micronutrient intakes among Central Texas WIC infants and toddlers after the package change

OBJECTIVE

To assess nutrient intakes after the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) package changes within an at-risk, majority Hispanic population of WIC infants and toddlers in Central Texas.

METHODS

For this cross-sectional observational study, Nutrition Data System for Research was used to collect 24-hour recalls of infants and toddlers from a sample of caregivers in 2009 and 2011. Usual nutrient intakes were estimated and compared with Dietary Reference Intakes using the National Cancer Institute method. Mean single-day nutrient intakes were compared using Mann-Whitney tests.

RESULTS

Subjects were children ages 4-24 months (2009, n = 84; 2011, n = 120). After the package change, usual energy intakes exceeded recommended levels for infants (79% in excess of Estimated Energy Requirement), but fell below recommended levels for toddlers (88% below Estimated Energy Requirement). Also after the package change, mean usual intake of vitamin D was below the Estimated Average Requirement for toddlers (6.54 vs 10 μg), and mean usual intakes of vitamin A and zinc exceeded the Tolerable Upper Intake Level for all groups.

CONCLUSIONS AND IMPLICATIONS

Whereas lower energy intake may reduce obesity risk, in toddlers, lower energy intake increases risk for micronutrient deficiencies. Recommendations include culturally appropriate education and reinstatement of previous milk allotment in the toddler package.