A 38-year-old female presents to the clinic with complaints of alternating diar-
rhea and constipation. She reports some abdominal discomfort and bloating
that are relieved with her bowel movement. She states that her episodes are
worse in times of stress. She denies any blood in her diarrhea. She denies any
weight loss or anorexia. Her physical exam is all within normal limits. She has
been prescribed a cellulose-containing dietary supplement, which her doctor
says will increase the bulk of her stools.
What is the most likely diagnosis?
What is the biochemical mechanism of the dietary supplement’s
effect on the intestines?