If you've been shoveling down high-fiber cereals every morning in hopes of preventing colon cancer, you can stop. 

The 30-year-old notion that cereal fiber reduces colon cancer risk is turning out to be yet another government-sanctioned myth. It may be time for the Food and Drug Administration to butt out of our colons. 

A study published in this week's The Lancet reports that a "... high-fiber diet and supplementation with wheat bran fiber may not be effective strategies for the prevention of [colon cancer]." 

By itself, the study would not be overly persuasive. But it is the fourth study in a major medical journal in the last two years to reach the same conclusion, including a January 1999 study in the New England Journal of Medicine that followed about 89,000 women over a period of 16 years. 

How did the myth get started? 

British medical missionary Dr. Denis Burkitt gave birth to the idea that dietary fiber reduced colon cancer risk in 1971. Burkitt observed — almost casually, not in any scientific manner — that poor rural Africans had much less colon cancer than Westerners. He theorized this was due to the Africans' fiber-rich diet. 

The idea was that larger, faster moving stools reduced the colon's exposure to carcinogenic bile acids. The theory's intuitive appeal propelled it to become conventional wisdom. But it lacked persuasive scientific support. 

Some studies seemed to support the theory; others did not. None of the studies were particularly well-designed — they tended to be retrospective in nature, relying on unverified self-reports of subjects' dietary and lifestyle habits. 

The National Research Council, the research arm of the National Academy of Sciences, thought the theory was so speculative that it declined in 1982 to make a specific recommendation about dietary fiber and colon cancer. 

Eventually, though, commercial interests perceived value in the theory and the scientific controversy became a memory. 

In 1984, cereal manufacturer Kellogg placed a message on its All Bran cereal claiming scientific evidence linking a high fiber diet with a reduction in colon cancer risk. The FDA took no action against Kellogg, though the claim seemed to defy a longstanding FDA rule prohibiting health-related messages on food products. 

The National Research Council reversed itself and came out in favor of a link between dietary fiber and reduced colon cancer risk in 1989 — though the state of the science had not changed. 

A 1990 federal law clarified the FDA's authority over food label content and the agency subsequently issued rules permitting health-claims labeling, provided there was some scientific support. 

In a 1997 effort to boost stagnant cereal product sales, Kellogg petitioned the FDA for permission to make the claim that some of its products contain ingredients that may help prevent certain cancers, especially colon cancer. 

In July 1999, the FDA permitted whole-grain foods to claim on their labels that "diets rich in whole-grain foods and other plant foods and low in total fat, saturated fat and cholesterol may reduce the risk of heart disease and certain cancers." 

The FDA did not give the scientific research on whole-grain foods the scrutiny that goes into the approval of a new drug. Instead, the agency relied on recommendations made by the NRC 10 years earlier. The FDA ignored the NEJM study that was published six months before the approval of the Kellogg petition — even though it was the largest study ever on dietary fiber and colon cancer. 

The result of the FDA's scientific sloth is that millions of consumers will continue to be misled for the foreseeable future about an important health issue — all the while choking down bran cereals and imagining they're preventing colon cancer. Certainly whole grains are part of a balanced diet. But by overestimating the benefits, many will have a false sense of security. 

And while the FDA is allowing companies to market junk science-fueled myths, the agency uses junk science to remove a product with known benefits. Maybe you've noticed that your favorite laxative doesn't work as well as it used to. 

Researchers from the U.S. government's National Toxicology Program reported to the FDA in April 1997 that mice fed high doses of the compound phenolphthalein had higher rates of cancer. At the time, phenolphthalein was the most effective active ingredient in laxative products. 

The FDA bullied laxative manufacturers to reformulate their products without phenolphthalein despite that: (1) the mice were genetically engineered to be more susceptible to cancer — they were, in a sense, "cancer time bombs"; (2) the doses of phenolphthalein were 30 times higher than consumer use; and (3) phenolphthalein was used as a laxative ingredient for more than 100 years with absolutely no indication of increased cancer risk among users. 

The several scientific studies published after the FDA decision also failed to link laxative-use with increased cancer risk. 

Hey, who needs laxatives when you've got bran? 

President Clinton this week announced a new effort to fight colon cancer, including, among other recommendations, that adults over the age of 50 have annual colon cancer screenings. Every year, there are an estimated 130,000 new cases of colon cancer and more than 50,000 deaths from the disease. 

Colon cancer may be cured if detected early enough. It's too bad there doesn't seem to be any cure for junk science at the FDA. 

— Steven Milloy is a biostatistician, lawyer, adjunct scholar at the Cato Institute and publisher of Junkscience.com.