If symptoms are recent in origin, testing may be needed to be certain that an infection, inflammation, or tumor is not responsible for the symptoms. The first step in managing IBS should be to identify what triggers the symptoms. The factors to consider include food intolerances, eating habits, dietary factors, emotional stress, exercise habits, use of laxatives, and vitamin C intake. It may help to keep a diary that relates symptoms to daily activities. This results from a shortage of lactase, an enzyme normally produced by cells lining the small intestine.
Lactase breaks down milk sugar into simpler substances that are absorbed into the bloodstream.
When there is not enough lactase, undigested lactose can ferment in the large intestine and cause nausea, cramps, bloating, flatulence, and diarrhea that begin about 30 minutes to 2 hours after consuming lactose-containing foods. The severity of symptoms varies with the amount of lactose the individual can tolerate. To determine whether lactose intolerance is a factor in IBS, the patient can experiment to see whether symptoms are related to milk intake. Laboratory testing may also be useful. Bloating or excessive gas can also be related to eating habits and diet.