The publication in April 2000 of the results of a clinical trial that found high fibre cereals had no protective effect against colorectal adenomas stirred up considerable media attention and shook a cherished tenet of popular health culture.1 After all, boxes of All-Bran have been assuring us for nearly two decades that they contain “at last, some news about cancer you can live with,”2 and the manufacturers of high fibre cereals have enjoyed unprecedented profits thanks to the assumption that their products provide insurance against colon cancer. What will happen to “the high fibre feeding frenzy”3 that has possessed Americans for the past 20 years now that that assumption has been challenged? #### Summary points Throughout human history, bowel irregularity has been considered to be dangerous to health In the 19th century medical scientists formulated a theory of “intestinal autointoxication”—self poisoning from one's own retained wastes The public became prey to marketers of anticonstipation foods, drugs, and devices; All-Bran was introduced in the early 1900s to combat autointoxication Recent clinical evidence suggests that cereal rich in fibre does not have a protective effect against bowel cancer, but because constipation has a historic hold over the public mind, people may continue to believe that bran is protective Not much, most likely. It isn't just that the epidemiologists continue to remind us that there are many observational studies of population groups that show a correlation between consumption of a bulky diet and low incidence of colorectal cancer,4 or that the gastroenterology authorities continue to recommend daily ingestion of a minimum of 30 grams of fibre.5 More important than anything the experts have to say, I would wager, is human intuition, which has seen bowel irregularity to be dangerous from as far back as health literature can be traced. The oldest …