The purpose of this study is to:

1. To determine if fiber versus placebo improves symptoms in children with recurrent abdominal pain/irritable bowel syndrome.
2. To determine possible ways fiber or placebo improve(s) symptoms in children with recurrent abdominal pain/irritable bowel syndrome by carrying out gastrointestinal tests and questionnaires.

Understanding how diet and fiber affect GI function potentially will benefit the large numbers of children with irritable bowel syndrome (IBS) and provide insight into prevention of IBS in at risk children. We expect that the results from these studies can be used to lessen significantly the huge financial burden to society caused by these chronic conditions.

Consent will be obtained from the parent/guardian and assent from the child.

Children with recurrent abdominal pain (RAP) who meet the criteria for irritable bowel syndrome (IBS) will be recruited and studied. They will have been diagnosed by a pediatric gastroenterologist and will have had at least one healthcare visits in the past year for the complaint of abdominal pain.

Coordinators will come out to the family's home on an evening that is convenient. Both the parent and child will fill out some questionnaires. Next, the parent and child will get instructions on how to fill out a diary to record any stomach pain the child is having and what their stools look like. The child will also collect a stool sample during the regular diet and diary collection period. Once the child has completed the diary, the child will go on a special diet for eight days to remove foods that may cause stomach pain (foods and drinks containing lactose, fructose, and sorbitol will be eliminated).

Two weeks later, the coordinators will come out to the family's home again to review the pain and stool diary that the child kept while on the special diet. The coordinators will explain how to collect some samples of urine, stool, and breath. These tests will evaluate the gastrointestinal (GI) tract for inflammation and transit time. If the special diet does not make the stomach pain go away, the child will be selected at random, like the flip of a coin, to be placed in one of two groups: one group that receives fiber or one group that receives a placebo or sugar pill. Fiber has been suggested to help children with stomach pain.

After the child has been on the treatment for 6 weeks, he/she will keep another diary and collect another set of samples of urine, stool, and breath.

The children will be followed at 3 months, 6 months and 18 months after the treatment period.

Children will be asked to collect additional stools

Inclusion Criteria:

• Children who have had at least one physician visit in the past year for abdominal pain or IBS symptoms.
• Children with recurrent abdominal pain who meet the criteria for irritable bowel syndrome.

Exclusion Criteria:

• Children who have another disease that accounts for stomach pain
• Current use of anti-inflammatory medication
• Children taking a GI medication that makes pain go away completely
• Children with other chronic conditions including chronic pain conditions (e.g. heart condition, diabetes)
• Children who have decreased growth
• GI blood loss
• Unexplained fever
• Chronic severe diarrhea
• Weight loss of > or = to 5% of body weight within 3 month prior to enrollment
• History of abdominal surgeries
• A history of suicide
• Cognitive impairment significantly below average age and/or grade level
• Non-English speaking parent or child
• Vomiting >2x/month
• Children currently in psychotherapy for abdominal pain.