Fiber Moral


Even for those who are not preoccupied with their colons, the recent news about fiber was cause for dismay. That dietary fiber reduced the risk of colon cancer was something we thought we knew, but here were two rigorous studies that suggested otherwise.

Despite the disappointment and confusion it caused, the episode was salutary in at least once respect: It highlighted the provisional nature of medical science.

The idea that eating fiber helps ward off colon cancer, widely accepted since the 1970s, was a plausible hunch that was supported by preliminary evidence. But in two large, randomized studies reported last month in The New England Journal of Medicine, people who ate high-fiber diets were no less likely to develop colon polyps, which can be precursors to cancer, than people who ate normal diets.

All of the subjects had already had at least one polyp removed, and the results might have been different with broader samples, or with longer follow-up periods. Still, the findings cast serious doubt on the conventional wisdom about fiber and colon cancer.

But even if that wisdom is mistaken, that doesn't mean the experts were wrong to recommend fiber all these years. Leaving aside fiber's other health benefits, the limited evidence about colon cancer may have been enough reason to eat more fruits, vegetables, and whole grains. Doing so entailed little risk, and if the fiber hypothesis turned out to be right, many people could have died needlessly while waiting for it to be confirmed.

Preventive medicine is largely a matter of playing the percentages, weighing possible benefits against possible harms. It may be perfectly rational to act on inconclusive evidence, because failing to act has its own risks.

That's a reality the Food and Drug Administration does not like to admit. Its policy regarding health claims for dietary supplements requires "significant scientific agreement"–a reasonable-sounding but fuzzy standard that in practice has barred all but two statements proposed by manufacturers.

More than a year ago, the U.S. Court of Appeals for the D.C. Circuit ordered the FDA to change its approach. "The FDA must explain what it means by significant scientific agreement or, at a minimum, what it does not mean," the court said, describing the agency's working definition as "I know it when I see it."

The court was responding to a First Amendment challenge by supplement designers Durk Pearson and Sandy Shaw, who had sought permission to use four cautiously worded health claims on their products. To address the FDA's concern that the statements were misleading, they offered to include a disclaimer such as, "The FDA has determined that the evidence supporting this claim is inconclusive."

Although the appeals court said the FDA should consider that approach, the agency still has not approved any of Pearson and Shaw's label statements, even with a disclaimer. Their attorney, Jonathan Emord, has asked the U.S. District Court in D.C. for a preliminary injunction barring the FDA from continuing to block health claims based on the rationale the appeals court rejected.

"FDA does not seem to have gotten the message yet that it too must comply with the Constitution," Emord recently told an industry newsletter. "Four FDA rules were held invalid under the First Amendment….Those four rules…are still being enforced."

One of the statements rejected by the FDA was, "Consumption of fiber may reduce the risk of colorectal cancer." In light of the recent fiber studies, the agency's censors probably feel vindicated.

They shouldn't. If anything, the statement proposed by Pearson and Shaw was more cautious than the advice routinely offered by physicians, medical writers, and public health officials.

If that advice was wrong, it wasn't because these people were trying to mislead anyone. They were giving what they thought was the best guidance they could, based on the evidence available at the time.

Further research may cast doubt on other hypotheses that Pearson and Shaw want to mention on their labels, such as the possible usefulness of antioxidant vitamins in preventing cancer or omega-3 fatty acids in preventing coronary heart disease. But that does not mean they are perpetrating a fraud by calling attention to the existing evidence.

People are bound to disagree about such matters. It's out of these disagreements, and the research they stimulate, that our knowledge improves. Pearson and Shaw would like to participate in this debate, if only the FDA would let them.