The invention relates to methods and compositions for the treatment of irritable bowel syndrome (IBS) and other functional gastrointestinal disorders. The methods of the invention involve the administration, in a delayed-release capsule or tablet containing a mixture of peppermint oil and chlorophyll. Other ingredients that may also be effective treatments may be included. This method may be useful as a new and safer treatment for IBS and other functional gastrointestinal disorders. The action of the peppermint oil is effective as a modulator of gastrointestinal motility and sensation. Chlorophyll may improve bowel activity by stimulation of secretion and motility. This is the first description of this unique mixture of these natural products for the treatment of gastrointestinal conditions.