VDR and Diarrhea: Therefore, the defensive effect of vitamin D in bacterial diarrhea can be defined by these mechanisms, which increase resistance against invading pathogenic organisms in the intestine, including Shigella and Salmonella. Similarly, animal studies have shown that reduced Salmonella invasion is associated with VDR expression, and anti-bactericidal effects on E. coli have been found in vitamin D-regulated antimicrobial peptides [10].