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

Epigallocatechin gallate alleviated the in vivo toxicity of ZnO nanoparticles to mouse intestine

To evaluate the oral toxicity of nanoparticles (NPs), it is necessary to consider the interactions between NPs and nutrient molecules. Recently, we reported that epigallocatechin gallate (EGCG), a healthy component in green tea, alleviated the toxicity of ZnO NPs to 3D Caco-2 spheroids in vitro. The present study investigated the combined effects of EGCG and ZnO NPs to mice in vivo. Mice were administrated with 35 or 105 mg/kg bodyweight ZnO NPs with or without the presence of 80 mg/kg bodyweight EGCG via gastric route, once a day, for 21 days, and the influences of EGCG on the toxicity of ZnO NPs to intestine were investigated. We found that EGCG altered the colloidal properties of ZnO NPs both in water and artificial intestine juice. As expected, ZnO NPs induced toxicological effects, such as decreased bodyweight, higher Chiu's scores, and ultrastructural changes in intestine, whereas EGCG alleviated these effects. Combined exposure to EGCG and ZnO NPs also changed trace element levels in mouse intestine. For example, the levels of Ti, Co, and Ni were only significantly elevated after co-exposure to EGCG and ZnO NPs, and Fe levels were only significantly decreased by ZnO NPs. Western blot analysis suggested that tight junction (TJ) and endoplasmic reticulum (ER) proteins were elevated by ZnO NPs, but EGCG inhibited this trend. Combined, these data suggested that gastric exposure to ZnO NPs induced intestinal damage, trace element imbalance, and TJ/ER protein expression in mouse intestine, whereas EGCG alleviated these effects of ZnO NPs.

The Role of Zinc in Bone Tissue Health and Regeneration-a Review

Zinc is a micronutrient of key importance for human health. An increasing number of studies indicate that zinc plays a significant role in bone tissue's normal development and maintaining homeostasis. Zinc is not only a component of bone tissue but is also involved in the synthesis of the collagen matrix, mineralization, and bone turnover. It has been demonstrated that zinc can stimulate runt-related transcription factor 2 (Runx2) and promote the differentiation of osteoblasts. On the other hand, zinc has been found to inhibit osteoclast-like cell formation and to decrease bone resorption by stimulating osteoclasts' apoptosis. Moreover, zinc regulates the RANKL/RANK/OPG pathway, thereby facilitating bone remodeling. To date, not all mechanisms of Zn activity on bone tissue are well understood and documented. The review aimed to present the current state of research on the role of zinc in bone tissue, its beneficial properties, and its effects on bone regeneration. Since calcium phosphates as bone substitute materials are increasingly enriched in zinc ions, the paper included an overview of research on the potential role of such materials in bone filling and regeneration.

Food sources of zinc and nutritional status with usual dietary zinc intake in Korean toddlers and preschool children

BACKGROUND/OBJECTIVES

This study aimed to evaluate the food sources of zinc and the usual intake of dietary zinc among Korean toddlers and preschool children.

SUBJECTS/METHODS

A total of 2,679 children aged 1-5 years was selected from the 2009-2013 Korea National Health and Nutrition Examination Survey (KNHANES) data. Dietary data collected from a single 24-h recall were used to evaluate the food sources of zinc. To estimate usual zinc intake, the distribution obtained from single 24-h recall data in the total sample was adjusted using the ratio of within-to-between-person variance in zinc intake obtained from 2-day 24-h recall sub-sample data of the 2009 KNHANES. The proportion of children with usual zinc intake below the estimated average requirement (EAR) and above the tolerable upper intake level (UL) was assessed.

RESULTS

The main sources of zinc in Korean children were grains, dairy products, and meat. The mean usual intakes of zinc among all individuals, those aged 1-2 yrs, and those aged 3-5 yrs were 5.50, 5.01, and 5.83 mg/d, respectively. In all participants, 1.1% of the children consumed zinc below the EAR, whereas 10.7% exceeded the UL. The proportion of children with excessive zinc intake was 25.6% in the 1-2 yrs age group and 0.6% in the 3-5 yrs age group.

CONCLUSIONS

According to the current UL, the risk of excessive zinc intake appears to be high among Korean toddlers. Future studies that monitor the health effects of excessive zinc intake are needed to appropriately guide zinc intake in children.

Dietary supplements increase the risk of excessive micronutrient intakes in Danish children

PURPOSE

Dietary supplement use is common in Northern Europe. Many dietary supplements contain 100% of nutrient reference values (NRV) of micronutrients. This study investigates the contribution of dietary supplements to micronutrient intake, the prevalence of excess intake of micronutrients, and parental characteristics of dietary supplement use in Danish children.

METHODS

Data on 499 4-10-year-old children from the Danish National Survey of Diet and Physical Activity 2011-2013 were analysed using non-parametric statistics to compare micronutrient intake from the diet and dietary supplements to the reference intake (RI), and to the tolerable Upper Intake Level (UL) for users and non-users of dietary supplements. Furthermore, characteristics of the parents of users and non-users of dietary supplements were examined by logistic regression analysis.

RESULTS

Sixty-four percent of the children were dietary supplement users. Multivitamin-mineral supplements were the most frequently used type of supplement (60%). Children of never-smokers were more likely to use supplements than children of smokers. Users had significantly higher total intakes of 15 micronutrients compared to non-users. Intakes of vitamin A, zinc, and iodine from the diet alone exceeded ULs in 12-30% of the children. Use of dietary supplements gave rise to 21-73% of children in exceedance of the aforementioned three ULs as well as the UL for iron (6-45%).

CONCLUSION

Dietary supplement use was common among 4-10-year-old Danish children and resulted in a considerable proportion of users exceeding the ULs for vitamin A, zinc, iodine, and iron. The long-term health consequences of exceeding these ULs for children are unknown.

Zinc Fortification: Current Trends and Strategies

Zinc, through its structural and cofactor roles, affects a broad range of critical physiological functions, including growth, metabolism, immune and neurological functions. Zinc deficiency is widespread among populations around the world, and it may, therefore, underlie much of the global burden of malnutrition. Current zinc fortification strategies include biofortification and fortification with zinc salts with a primary focus on staple foods, such as wheat or rice and their products. However, zinc fortification presents unique challenges. Due to the influences of phytate and protein on zinc absorption, successful zinc fortification strategies should consider the impact on zinc bioavailability in the whole diet. When zinc is absorbed with food, shifts in plasma zinc concentrations are minor. However, co-absorbing zinc with food may preferentially direct zinc to cellular compartments where zinc-dependent metabolic processes primarily occur. Although the current lack of sensitive biomarkers of zinc nutritional status reduces the capacity to assess the impact of fortifying foods with zinc, new approaches for assessing zinc utilization are increasing. In this article, we review the tools available for assessing bioavailable zinc, approaches for evaluating the zinc nutritional status of populations consuming zinc fortified foods, and recent trends in fortification strategies to increase zinc absorption.