The Effect of Zinc on Appetite and Nutritional Status in Children: A Systematic Review

Abstract

Background: Zinc is essential for growth, immune function, and numerous cellular processes. Zinc deficiency-prevalent in over 20 of children in low-and middle-income countries-is associated with stunted growth, cognitive impairment, and increased susceptibility to infections. Low zinc status may also impairtaste perception, thereby reducing appetite and exacerbating nutritional deficiencies. Objectives: This study aimed to evaluatethe effects of dietary zinc intake and/or supplementation on appetite and growth in healthy children aged 6 months to 18 years. Methods: Following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, we conducted a comprehensive search of PubMed, Web of Science, and Scopus for observational studies, prospective and retrospective cohort studies, case-control studies, and randomized controlled trials (RCTs) published between April 2015 and January 2024. Reference lists were also reviewed. The review protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42024578984). Studies assessing zinc status or intake (via supplementation or diet) and its relationship with appetite orgrowth in healthy children were included. Results: Of the 1,797 initial studies, 23 studies from 14 countries involving 79,319 participants aged 6 months to 18 years met the eligibility criteria and were included. Zinc supplementation doses ranged from 3 to 20 mg/day and were administered for durations between 1and 24 months. Of the 23 studies, 10 examined zinc supplementation alone, and 7 assessed both dietary zinc intake and supplementation. Appetite was evaluated in nine studies (five RCTs, four observational studies). Five studies (55.6, all RCTs) reported significant improvements in appetite among zinc-deficient children (level I evidence), whereas four studies (44.4, two RCTs, two observational studies) reported no significant effect (level I and II evidence). Growth outcomes were assessed in all 23 studies (12 RCTs and 11 observational studies). Sixteen studies (69.6, nine RCTs and seven observational studies) demonstrated significant improvements in weight-for-age (WAZ) and height-for-age (HAZ) Z-scores (Level I and II evidence), particularly among zinc-deficient or malnourished children. Seven studies (30.4, three RCTs and four observational studies) reported no significant effect (level I and II evidence). Zinc levels were measured in 18 studies using plasma or serum analysis, and 10 studies used placebo-controlled designs. Conclusions: Zinc supplementation demonstrates variable but generally positive effects on appetite and growth in healthy children, with stronger benefits in zinc-deficient or malnourished populations. The evidence (primarily level I from RCTs) supports zinc's role in improving appetite and growth in specific contexts; however, inconsistencies across studies highlight the need for further research to optimize supplementation protocols and explore synergistic effects with other micronutrients.