The purpose of this study is to determine whether administration of glucomannan (dietary fiber) is effective in treating functional constipation in children.

Constipation is a common condition in children. In many patients symptoms persist to adulthood and decrease quality of life. The standard treatment, mostly osmotic laxatives such as lactulose or polyethyleneglycols, are often ineffective and may cause adverse events. Therefore, alternative treatment measures are being searched for.

Glucomannan, a water-soluble fiber polysaccharide from the tubers of the Japanese Konjac plant, has been reported to be effective in constipated children. To date, 2 randomized trials were performed.1,2 One evaluated the effect as glucomannan as an adjunct to standard treatment.1 Another was conducted in neurologically impaired children, who constitute a specific population that cannot be compared to patients with functional constipation.2 In both trials, the number of patients was relatively small.

Well-powered, randomized controlled study is required to evaluate clinical effectiveness of glucomannan as a sole treatment in childhood functional constipation.

Inclusion Criteria:

• functional constipation diagnosed according to Rome Criteria III (duration of symptoms for at least 2 months prior to study inclusion)
• age 3 to 16 years
• informed consent from parents and/or child

Exclusion Criteria:

• organic cause of defecation disorders (Hirschsprung's disease, spinal anomalies or anorectal pathology; history of gastro-intestinal surgery)
• mental retardation
• metabolic disease (e.g. hypothyroidism)
• irritable bowel syndrome
• intake of medications influencing gastrointestinal motility

The participants and researchers conducting the study were blinded. Intervention products were prepared in sachets centrally by the hospital pharmacy by a person not involved in the conduct of the trial. The active product and placebo were packaged in identical sachets and labeled with one of two codes, each allocated to the experimental product or placebo. This procedure was performed by an independent pharmacist, who was the only person aware of the codes' meaning. The appearance and texture of the dry products were identical.