Background: Worldwide, children have a very high prevalence of vitamin D deficiency. Epidemiological evidence connects vitamin D deficiency to immune system dysfunction and an elevated risk of infections. For the therapy of acute diarrhea in children, it may be useful to know how vitamin D deficiency affects the severity of the condition.
Objectives: To study the relation between vitamin D deficiency and recurrent acute diarrhea in children.
Patients and Methods: A Hundred Egyptian children (1 month to 5 years old) with a history of recurrent attacks of acute diarrhea were enrolled in the study. They were subjected to complete history, clinical examination and laboratory investigation including vitamin D assays.
 Results: we found a positive correlation between vitamin D deficiency and recurrent acute diarrhea. Vitamin D deficiency was deficient in 15%, insufficient in 17%, and sufficient in 68% of children with recurrent acute diarrhea. There was a significantly decreased percentage of vitamin D supplementation in deficient patients (20%) when compared with insufficient patients (64.7%) and sufficient patients (63.2%). There was a highly significantly increased total number of diarrhea episodes in deficient patients (5.6 ± 1.1) when compared with insufficient patients (4.3 ± 1.5) and sufficient patients (2.2 ± 0.9).
Conclusion: This study pays attention to the role of vitamin D in the susceptibility to infection-related illness in children.