Background & Objectives : Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is common through the world including Iran. Because of its chronic nature and lack of effective treatment, patients are always anxious and stressful and physicians are also exhausted of untreated patients. The cause of IBS is unclear and it has not effective treatment. Therefore, there is a need to find and introduce a proper method of treatment to control symptoms including abdominal pain and defecation changes. This study was aimed to determine the effectiveness of probiotic yogurt on the general relief of symptoms associated with IBS.

  Methods : Subjects were recruited from patients of gastroenterology clinic in Imam Khomeini Hospital, Ardabil. A total of sixty patients fulfilling the Rome II criteria took part in this study. Subjects were randomized into two groups of trial and control. Pre- and post- treatment symptoms were investigated using a questionnaire. Thirty one patients received probiotic and 29 patients normal yogurt for 4 weeks. Bottles of yoghurt were manufactured, and coded by a company. Both participants and researcher were blinded for the bottles' code. The symptoms were followed before and after two and four weeks of treatment and two weeks post- discontinuing of trial, too. Data were analyzed by SPSS (Ver. 17) and differences between groups were compared statistically using of chi-square and t-test.

  Results: A total number of 60 patients were recruited in this study of whom 36 (60%) were female and 24(40%) male. The average age of participants was 34.1±9 which did not differ between two groups. The onset of symptoms did not show any difference between two groups. The trial group had a history of 5.7±5.1 years while this was 6.5±4.9 for the controls. In overall, patients who were given probiotic yogurt had shown a better response in the control of abdominal pain and flatulence than those who were treated with normal yogurt. There was not a significant difference between two groups in the response to treat for other symptoms including epigastric pain, vomiting, frequency of defecation and feces consistency.

  Conclusion: According to our research, adding probiotic yogurt to the patient diet may help ease symptoms of IBS especially, abdominal pain and flatulence. Considering the high prevalence of irritable bowel syndrome and the lack of effective therapies, even a slight reduction in symptoms can have positive public health consequences.