How can probiotic improve irritable bowel syndrome symptoms?

Table 1 Summary of diagnostic criteria used to define irritable bowel syndrome

Diagnostic criteria	Symptoms included in criteria
Rome 1 (1990)	Abdominal pain or discomfort relived with defecation; Abdominal pain or discomfort associated with a change in stool frequency or consistency; In addition, two or more of the following on at least 5% of occasions or days for 3 mo: (1) Altered stool frequency and form; (2) Altered stool passage; (3) Passage of mucus; and (4) Bloating or distension
Rome II (1999)	Abdominal discomfort or pain that has two or three features for 1 wk (need to be consecutive) in the last year; Relieved with defecation; Onset associated with a change in the frequency of stools; Onset associated with a change in the form of stools
Rome III (2006)	Recurrent abdominal pain or discomfort three days per month in the last 3 mo associated with two or more of: (1) Improvement in defecation; (2) Onset associated with a change in the frequency of stools; and (3) Onset associated with a change in the form of stools
Rome IV (2016)	Recurrent abdominal pain on average at least 1 d/wk in the last 3 mo, associated with 2 or more of the following1: (1) Related to defecation (i.e., either increasing or improving pain); (2) Associated with a change in stool frequency; and (3) Associated with a change in stool form (appearance)

¹Criteria fulfilled for the last 3 mo with symptom onset at least 6 mo before diagnosis.