In 1992, the Center for Disease Control (CDC) reported the first national guideline, emphasizing the emergency of the treatment of childhood diarrhea and the importance of zinc supplementation.3 Since then, a variety of trials have been established, lifescience especially in developing countries, to assess the effect of zinc supplementation on the duration and severity of diarrhea.4-13 The beneficial effects of zinc supplementation on childhood diarrhea have been discussed in several studies,8,9,14,15 yet the exact underlying mechanisms leading to these favorable effects are still unclear. Zinc is an essential trace element for humans.16,17

Some plausible mechanisms might be improved absorption Inhibitors,research,lifescience,medical of water and electrolytes by the intestine, faster regeneration of gut epithelium, increased levels of enterocyte brush

border enzymes, and enhanced immune response, conferring early clearance of diarrheal pathogens from the intestine.18,19 Given these findings, Inhibitors,research,lifescience,medical zinc supplementation is currently recommended as a universal treatment for all children with acute gastroenteritis.13,15 Be that as it may, some other scientists, particularly in developed countries, believe Inhibitors,research,lifescience,medical that there is not enough evidence to support its routine use.20 Despite the reported encouraging benefits of zinc supplementation in childhood (up to 18% decline in children with acute diarrhea frequency),12 the cost effectiveness of such treatment is still arguable.21-23 Although there are numerous studies evaluating the safety and efficacy of zinc supplementations in the treatment of acute gastroenteritis 7-11,14,24 and its proven effects on persistent diarrhea,25 there have been only a few studies about Inhibitors,research,lifescience,medical the potential beneficial effects of zinc supplementation on selected categories of acute diarrhea. The lack of a well-designed randomized trial assessing the effects of zinc supplements on the severity and duration of diarrhea in Iran, as a developing country, renders new research necessary. This study was, therefore, designed to compare the severity Inhibitors,research,lifescience,medical and duration of diarrhea between patients with acute diarrhea who received zinc plus oral rehydration solution

(ORS) and those who received only routine ORS. Materials and Methods Study Design, Inclusion and Exclusion Criteria This double-blind randomized clinical Cell Stem Cell trial (RCT) recruited all 9-month to 5-year-old children who were admitted with acute watery diarrhea and moderate dehydration to the Children Ward of Motahari Hospital, Urmia, Iran in 2008. The exclusion criteria were comprised of diagnosed chronic diseases (cystic fibrosis, inflammatory bowel diseases, and malabsorption), severe malnutrition (weight curve was under 3% for age), dysentery and bloody diarrhea confirmed with the existence of red blood cells (RBC) or white blood cells (WBC) in stool examination (S/E), recent consumption of antibiotics, severe dehydration or persistent vomiting, recent consumption of zinc supplements (last month), and drug intolerance.