Beneficial effects of zinc supplementation on head circumference of Nepalese infants and toddlers: a randomized controlled trial

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.

Anthropometric proxies for child neurodevelopment in low-resource settings: length- or height-for-age, head circumference or both?

Stunting (<-2 SD of length- or height-for-age on WHO growth curves) is the most used predictor of child neurodevelopmental (ND) risk. Occipitofrontal head circumference (OFC) may be an equally feasible, but more direct and robust predictor. We explored association of the two measurements with ND outcome, separately and combined, and examined if cutoffs are more efficacious than continuous measures in predicting ND risk. Infants and young children in rural Guatemala (n = 642; age range = 0.1-35.9 months) were enrolled in a prospective natural history study, and their ND was tested using the Mullen Scales of Early Learning (MSEL) longitudinally. Length- or height-for-age and OFC-for-age were calculated. We performed age-adjusted multivariable regression analyses to explore the association between 1) length or height and ND, 2) OFC and ND, and 3) both length or height and OFC combined, with ND; concurrently, predictively, and longitudinally, as continuous variables and using WHO z-score cutoffs. Continuous length- or height-for-age and OFC z-scores were more strongly associated with MSEL than the traditional -2 SD WHO cutoff. The combination of height-for-age z-score and OFC z-score was consistently, strongly associated with the MSEL Early Learning Composite concurrently (p-values 0.0004-0.11), predictively (p-value 0.001-0.07), with the exception of the 18-24 months age group which had very few records, and in the longitudinal model (p-value <0.0001-0.004). The combination of continuous length- or height-for-age and OFC shows additional utility in estimating ND risk in infants and young children. Measurement of OFC may improve precision of prediction of ND risk in infants and young children.

A prospective cohort study of head circumference and its association with neurodevelopmental outcomes in infants and young children in rural Guatemala

Microcephaly, an anthropometric marker of reduced brain volume and predictor of developmental disability, is rare in high-income countries. Recent reports show the prevalence of microcephaly to be much higher in lower resource settings. We calculated the prevalence of microcephaly in infants and young children (n = 642; age range = 0.1-35.9 months), examined trends in occipitofrontal circumference (OFC) growth in the year after birth and evaluated the relationship between OFC and performance on the Mullen Scales of Early Learning (MSEL) in rural Guatemala. Multivariable regression analyses adjusted for age were performed: (1) a model comparing concurrent MSEL performance and OFC at all visits per child, (2) concurrent OFC and MSEL performance by age group, and (3) OFC at enrollment and MSEL at final visit by age group. Prevalence of microcephaly ranged from 10.1% to 25.0%. OFC z-score decreased for most infants throughout the first year after birth. A significant positive association between continuous OFC measurement and MSEL score suggested that children with smaller OFC may do worse on ND tests conducted both concurrently and ∼1 year later. Results were variable when analyzed by OFC cutoff scores and stratified by 6-month age groups. OFC should be considered for inclusion in developmental screening assessments at the individual and population level, especially when performance-based testing is not feasible.

Fasting Plasma Glucose Mediates the Prospective Effect of Maternal Metal Level on Birth Outcomes: A Retrospective and Longitudinal Population-Based Cohort Study

OBJECTIVE

Previously, we found that the presence of maternal serum metals before the 24th week of gestation prospectively increased fasting plasma glucose (FPG) at 24-28 weeks. We further explored the prospective association between levels of metals and neonatal outcomes and assessed the mediating effects of FPG on these relationships.

METHODS

A total of 7,644 pregnant women were included in a retrospective cohort study, and the relationships between metals [manganese (Mn), copper (Cu), lead (Pb), zinc (Zn), and magnesium (Mg)] and birth outcomes were explored. Quantile and linear regressions were performed to detect the shifts and associations between metals and neonatal size distribution focused on the 10th, 50th, and 90th percentiles. Mediation analysis was performed to assess the mediating effect of FPG on metals and birth outcomes.

RESULTS

After adjustment, a 50% increase in Mn and Zn levels was related to a 0.136-cm (95% CI: 0.067-0.205) and 0.120-cm (95% CI: 0.046-0.193) increase in head circumference, respectively. Based on head circumference distribution, the magnitude of the association with Mn was smaller at the upper tail, while the magnitude of correlation with Zn was greater at the upper tail. A 50% increase in Mn and Zn levels was related to a 0.135-cm (95% CI: 0.058-0.212) and 0.095-cm (95% CI: 0.013-0.178) increase in chest circumference, respectively. The magnitude of the association with Mn increased with increasing chest circumference, while the magnitude of correlation with Zn decreased with increasing chest circumference. FPG explained 10.00% and 17.65% of the associations of Mn with head and chest circumference. A positive indirect effect of Zn associated with head circumference (0.004, 95% CI: 0.002-0.006) and chest circumference (0.005, 95% CI: 0.003-0.008) through FPG was also observed, and the estimated proportion of the mediating effect was 13.79% and 26.32%, respectively.

CONCLUSION

Maternal serum Mn and Zn levels before the 24th week of gestation may prospectively increase the circumference of the neonatal head and chest. FPG at 24-28 weeks had positive mediating effects on these relationships. Further research is needed to identify a balance between maternal blood glucose and birth size.

Adolescent Cranial Volume as a Sensitive Marker of Parental Investment: The Role of Non-material Resources?

Growth of different body parts in humans is sensitive to different resource constraints that are mediated by parental investment. Parental investment can involve the expenditure of material, cognitive, and emotional resources on offspring. Cranial volume, an important predictor of cognitive ability, appears understudied in this context. We asked (1) whether there are associations between growth and family structure, self-reported estimates for resource availability, and sibling number; and (2) whether these constraints relate to head and body growth in a similar manner. We assessed the associations between parental investment, height, and cranial volume in a cross-sectional study of Estonian children (born 1980-87, aged 11-17). Height correlated negatively with the number of siblings but this association became negligible in a model controlling for birthweight, parental heights, and mother's age at birth. Unlike height, cranial volume was unrelated to sibling number, but it was negatively associated with self-reported meat and general resource shortage. Cranial volume was related to family structure and paternal education. Children living with both birth-parents had larger heads than those living in families containing a step-parent. Since these family types did not differ with respect to meat or general resource shortage, our findings suggest that families including both genetic parents provide non-material benefits that stimulate predominantly cranial growth. For the studied developmental period, cranial volume appeared a more sensitive marker of growth constraints than height. The potential of using cranial volume for quantifying physical impact of non-material parental investment deserves further attention.

Head growth of undernourished children in rural Nepal: association with demographics, health and diet

BACKGROUND

Brain development in early childhood is a key determinant of later cognition, social achievement and educational success. Head circumference (HC) measurements are a simple method to assess brain growth, yet reports of these measurements are uncommon in nutritional surveys of undernourished children.

OBJECTIVE

To evaluate HC measurements in a population of rural Nepali children and relate these measurements to demographics, health and diet.

METHODS

An observational study of head growth was nested within a longitudinal evaluation of a livestock-based agricultural intervention in rural Nepal. Between 538 and 689 children (aged 6 months to 8 years) were measured (height, weight, HC) at each of six survey visits. A total of 3652 HC measurements were obtained. Results were converted to Z-scores (WHO Anthro).

RESULTS

Mean head circumference Z-scores (HCZ) diminished progressively over the first 4 years of life; a decline of 30% occurred between 3 and 4 years of age (-1.73 to -2.45, P < 0.0001). Overall, 56% of HCZ were <-2. Gender-adjusted HCZ (but not other measurements) were significantly lower for girls than boys [mean (SD) -2.31 (1.0) vs -1.99 (0.094), P < 0.0001]; girls more often had microcephaly (61% vs 50%, P < 0.0001). For children <3 years of age, HCZ were better in those who had eaten two or more animal-source foods (ASFs) within the previous 24 h [-1.69 (.05) vs -2.08 (0.10), P = 0.001] than in those who had eaten none or only one; HCZ correlated with the number of ASFs consumed (P < 0.001). Regression analyses demonstrated that the main determinants of HCZ were age, weight-for-age Z-scores (WAZ) and gender; 43% of the variance in HCZ in younger children was explained by WAZ and ASF consumption.

CONCLUSION

HCs reflect brain size in young children; brain size is linked to cognitive function. Poor head growth represents another facet of the 'silent emergency' of child undernutrition. Routine HCZ assessments may contribute to better understanding of the links between poverty and cognitive development.

Early Zinc Supplementation and Enhanced Growth of the Low-Birth Weight Neonate

BACKGROUND:

Nutritional deficits are almost universal in Low-Birth Weight babies. Zinc is essential for normal infant growth and its supplementation assists growth probably through insulin-like growth factor-1.

AIM:

This double-blind randomized-controlled trial aimed at evaluating the role of zinc in catch-up growth of low-birth-weight infants and investigating its proposed mediator.

MATERIAL AND METHODS:

The study was conducted in Ain Shams University Maternity Hospital. Two hundred low-birth-weight neonates were simply randomized to either oral zinc therapy or placebo. Anthropometric measurements were recorded at birth, 3, 6, and 12 months; including weight, recumbent length, head, waist, chest, and mid-upper arm circumferences, and triceps and sub-scapular skin fold thickness.

RESULTS:

We found that initial and 3-months measurements, except weight, were comparable in the 2 groups. All measurements at 6- and 12-months, except sub-scapular skin-fold-thickness, were significantly higher in zinc group than placebo. Catch-up growth, at 12-months, was significant in zinc group and was significantly higher in appropriate-for-gestational-age vs. small-for-gestational-age, in preterm vs. term, and in male vs. female infants. The median 6-months insulin-like growth factor-1 levels were significantly higher in zinc group.

CONCLUSION:

We conclude that early start of oral zinc supplementation in low-birth-weight neonates assists catch-up growth, probably through rise of insulin-like growth factor-1.

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

BACKGROUND

Zinc deficiency is prevalent in low- and middle-income countries, and contributes to significant diarrhoea-, pneumonia-, and malaria-related morbidity and mortality among young children. Zinc deficiency also impairs growth.

OBJECTIVES

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

SEARCH METHODS

Between December 2012 and January 2013, we searched CENTRAL, MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, Embase, African Index Medicus, Conference Proceedings Citation Index, Dissertation Abstracts, Global Health, IndMED, LILACS, WHOLIS, metaRegister of Controlled Trials, and WHO ICTRP.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

Two authors screened studies, extracted data, and assessed risk of bias. We contacted trial authors for missing information.

MAIN RESULTS

We included 80 randomised controlled trials with 205,401 eligible participants. We did not consider that the evidence for the key analyses of morbidity and mortality outcomes were affected by risk of bias. The risk ratio (RR) for all-cause mortality was compatible with a reduction and a small increased risk of death with zinc supplementation (RR 0.95, 95% confidence interval (CI) 0.86 to 1.05, 14 studies, high-quality evidence), and also for cause-specific mortality due to diarrhoea (RR 0.95, 95% CI 0.69 to 1.31, four studies, moderate-quality evidence), lower respiratory tract infection (LRTI) (RR 0.86, 95% CI 0.64 to 1.15, three studies, moderate-quality evidence), or malaria (RR 0.90, 95% CI 0.77 to 1.06, two studies, moderate-quality evidence).Supplementation reduced diarrhoea morbidity, including the incidence of all-cause diarrhoea (RR 0.87, 95% CI 0.85 to 0.89, 26 studies, moderate-quality evidence), but the results for LRTI and malaria were imprecise: LRTI (RR 1, 95% CI 0.94 to 1.07, 12 studies, moderate-quality evidence); malaria (RR 1.05, 95% 0.95 to 1.15, four studies, moderate-quality evidence).There was moderate-quality evidence of a very small improvement in height with supplementation (standardised mean difference (SMD) -0.09, 95% CI -0.13 to -0.06; 50 studies), but the size of this effect might not be clinically important. There was a medium to large positive effect on zinc status.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, five studies, high-quality evidence). We found no clear evidence of benefit or harm of supplementation with regard to haemoglobin or iron status. Supplementation had a negative effect on copper status.

AUTHORS' CONCLUSIONS

In our opinion, the benefits of preventive zinc supplementation outweigh the harms in areas where the risk of zinc deficiency is relatively high. Further research should determine optimal intervention characteristics such as supplement dose.

Plasma zinc levels, anthropometric and socio-demographic characteristics of school children in eastern Nepal

Background

Zinc deficiency is a major public health problem in many developing countries including Nepal. The present study was designed to assess the prevalence of zinc deficiency and to study the association of zinc deficiency with anthropometric and socio-demographic variables, in school children of eastern Nepal.

Methods

This cross-sectional study included total 125 school children of age group 6–12 years from Sunsari and Dhankuta districts of eastern Nepal. Plasma zinc level was estimated by Flame Atomic Absorption Spectroscopy.

Results

The Median interquartile range (IQR) values of zinc in the two districts Sunsari and Dhankuta were 5.9 (4.4, 7.9) μmol/L and 5.8 (4.3, 8.4) μmol/L respectively. A total of 55 children (87.3%) in Sunsari and 52 (83.9%) in Dhankuta had zinc deficiency, no significant difference was observed in the Median (IQR) plasma zinc levels (p = 0.9) and zinc deficiency patterns (p = 0.3) of the two districts. Significant differences were observed in the plasma zinc levels (p = 0.02) and zinc deficiency patterns (p = 0.001), of the school children having age groups 6–8 years than in 9–10 and 11–12 years of age, and zinc deficiency patterns between male and female school children (p = 0.04) respectively.

Conclusions

The present study showed higher prevalence of zinc deficiency among school children in eastern Nepal. In our study, zinc deficiency was associated with both sex and age. The findings from the present study will help to populate data for policy implementation regarding consumption and supplementation of zinc.

Exposure to zinc oxide nanoparticles affects reproductive development and biodistribution in offspring rats

Understanding reproductive development effects and transferable properties to next generation of zinc oxide nanoparticles is necessary for prevention of its potential risks. To accomplish this, rats were exposed to zinc oxide nanomaterials (500 mg/kg bw) of less than 100 nm beginning 2 weeks before mating to postnatal day 4. In addition, body distribution of zinc concentration was evaluated in dams and offspring. Rat treated with nano-zinc oxide showed reduced number of born/live pups, decreased body weights of pups and increased fetal resorption. Zinc oxide nanomaterials were also distributed to organs such as mammary tissue of dams and liver and kidney of pups. These results indicate that zinc oxide nanoparticles-exposure before and during pregnancy and lactation could pose health risks to pregnant women and their fetus.