Tallying wheat bran's gutsy benefits.

Though many studies have indicated that diets high in wheat bran can reduce an individual's risk of developing colon cancer, the data have appeared somewhat equivocal, acknowledges David M. Klurfeld of Wayne State University in Detroit. Contributing to the problem, he notes, is the difficulty of documenting human diets. "People don't remember what they ate last Tuesday, much less 6 years ago."

However, he says, a few have failed to detect a wheat bran benefit even among animal studies, where diets can be "impeccably well controlled." To probe the significance of such contrary findings, Klurfeld conducted a metanalysis on some 30 well-designed studies that together included more than 3,000 rodents. Metanalysis combines data collected from numerous smaller studies--of mice and rats, in this case--in order to increase the statistical power of the inquiry.

Klurfeld observed a 32 percent reduction in colon cancer risk in animals that ate wheat bran, based on the data "from all of these studies--including those reporting no effect or an enhancement of risk." He says he was particularly "surprised by the very narrow range, 20 to 40 percent, on the [statistical] limits for this reduction." Further statistical analysis indicated that the finding is "very unlikely" to be overturned, even by 100 additional animal studies of similar size.

Klurfeld would like to perform a similar metanalysis of human studies on wheat bran's role in preventing colon malignancies, the third leading cause of cancer deaths in the United States.