Deficiency of Vitamin D should be considered as a comorbidity in children with diarrhoea in developing countries, and focused interventions to optimize the management of both diseases need to be implemented.

Systematic review and meta-analysis to explore the possible link between deficiency of Vitamin D and diarrhoea in childhood.

'Vitamin D deficiency', 'Vitamin D', '25-hydroxyvitamin D', 'diarrhoea', 'gastroenteritis', 'children', and 'pediatric' were the main keywords used to explore the PubMed, Ovid, Scopus, and Cochrane Library (from beginning to August 2022). Only English language, full-text studies were included. Unpublished trials, repositories, thesis, dissertations and conference paper abstracts were not included. The Newcastle-Ottawa quality assessment scale served as the tool for assessing bias risk.

Of the total 5,565 articles, twelve articles were included in this systematic review, but only 7 articles were qualified for meta-analysis. The meta-analysis revealed a noteworthy correlation between vitamin D deficiency and diarrhea among the pediatric population in developing nations (OR = 1.79; 95% CI = 1.15 to 2.80 with a p-value of 0.01). However, conflicting findings emerged regarding the link between vitamin D deficiency and the length or relapse of diarrhea as per the secondary outcome analysis.

An evident link exists between insufficiency of vitamin D and the incidence of diarrhoea. Subsequent research should aim at exploring the causal relationship as to how vitamin D deficiency influences diarrhoea severity, along with whether management of this vitamin deficiency affects diarrhoea prevalence needs to be investigated.