Zinc Deficiency and Immune Function in Children from Low- and Middle-Income Countries: A Systematic Review

Abstract

Zinc is an essential micronutrient required for several metabolic activities. It plays a key role in immune system function, growth, protein and DNA synthesis, and is also needed in the metabolism of over 200 enzymes. Its role in child growth and development cannot be overemphasized. Despite zinc's established immunological benefits, a significant knowledge gap exists regarding the prevalence, consequences, and impact of its deficiency on immunological function among children in low- and middle-income countries (LMICs). This review aims to establish the relationship between zinc deficiency and immune system function among children in LMICs. Literature databases were searched with keywords related to zinc deficiency, children, and immune function. The search included studies focused on children from 0 to 18 years in LMICs, assessing zinc status and immune- elated outcomes. The studies should have been published between 2010 and 2024 and published in English. Animal studies and editorials were excluded. Scopus, PubMed, Web of Science, Google Scholar, and Cochrane were searched for eligible articles. Data was extracted by 2 independent reviewers. Information obtained included characteristics of participants, assessments, immune parameters, and interventions. Prevalence of zinc deficiency ranged from 9.5 to 99%. Zinc deficiency in children significantly reduced T-cell counts, impaired cytokine regulation, and elevated inflammatory markers such as CRP and IL-6. Intervention studies reported that zinc supplementation significantly increases serum zinc concentrations. Supplementation was also found to reduce the incidence of diarrhea and pneumonia. Fortification showed moderate improvements with smaller effect sizes. Zinc deficiency in children remains a significant public health concern in LMICs and is strongly related to impaired function and heightened susceptibility to infections in children. Current evidence supports zinc supplementation and fortification as effective strategies for improving zinc status and immune outcomes.