John Harvey Kellogg was a leading advocate for the guesswork of autointoxication and, the legend goes, manufactured whole-grain cereals to promote regular bowel movements. (It was his brother, Will, who founded the Fray Creek Toasted Corn Flake Company, which later became the Kellogg Company.)

"It's all just nonsense," says Dr. Brian Lacy of Dartmouth Medical School, author of Legislative Touch of IBS: A Physician Answers Your Questions about Irritable Bowel oxy powder capsules Syndrome. With prices often topping $100 and sometimes elevated $1,000 for weeklong spa therapies, Lacy calls colon cleansing "a very expensive enema."