Vitamin D 3 supplementation as an adjunct in the management of childhood infectious diarrhea: a systematic review

Some studies have reported the possible role of vitamin D in ameliorating disease outcomes in childhood infectious diarrhea. However, findings about its effectiveness and the association of serum vitamin D levels with diarrhea risk appear inconsistent. We aimed to determine the efficacy of oral vitamin D as an adjunct in managing childhood infectious diarrhea and the relationship between vitamin D status and the disease. We searched the PubMed and Google Scholar electronic databases for relevant articles without limiting their year of publication. We selected primary studies that met the review's inclusion criteria, screened their titles and abstracts, and removed duplicates. We extracted data items from selected studies using a structured data-extraction form. We conducted a quality assessment of randomized controlled trials (RCTs) and non-randomized studies with the Cochrane collaboration tool and the Newcastle Ottawa Scale, respectively. We assessed the strength of the relationship between serum vitamin D levels and diarrhea using the correlation model. We estimated the I and tau values to assess between-study heterogeneity. Nine full-text articles were selected, consisting of one RCT, three cross-sectional studies, two cohort studies, two longitudinal/prospective studies, and one case-control study. A total of 5,545 participants were evaluated in the nine studies. Six non-randomized studies provided weak evidence of the relationship between vitamin D levels and diarrhea risk as there was no correlation between the two variables. The only RCT failed to demonstrate any beneficial role of vitamin D in reducing the risk of recurrent diarrhea. The calculated I and tau values of 86.5% and 0.03, respectively suggested a high between-study heterogeneity which precluded a meta-analysis of study results. Oral vitamin D may not be an effective adjunct in managing childhood infectious diarrhea. Additionally, the relationship between vitamin D status and infectious diarrhea appears weak. We recommend more adequately-powered RCTs to determine the effectiveness of vitamin D as an adjunct therapy in infectious diarrhea.