Fiber from whole grains reduces risk of bowel cancer: Study

By Dr. Ananya Mandal, MDNov 14 2011

A review of previous studies shows that high-fiber diet from whole grains could help ward off colorectal cancer.

The researchers from Britain and the Netherlands found that the more total dietary fiber and cereal fiber people consumed, the lower their colorectal cancer risk. For example, people who consumed an extra 90 grams of fiber from whole grains a day also had a 20 percent lower risk of colorectal cancer, according to the British Medical Journal review. However, these researchers didn't find that getting extra fiber from vegetables or fruits was linked with the decreased colorectal cancer risk, which means that there might be something else in the whole grains at works.

The review included results of 25 studies that involved nearly 2 million participants. They found that for each additional 10 grams of total dietary fiber and cereal fiber consumed a day, the person's colorectal cancer risk decreased by 10 percent.

Study researcher Dagfinn Aune, of Imperial College London, told WebMD that even if a person starts off with a low level of fiber consumption - say, 5 grams a day - and increase it by 10 grams - to 15 grams a day - that could still be beneficial at lowering colorectal cancer risk. “This study highlights the importance of a diet rich in fiber,” Dr. Anthony Starpoli, a gastroenterologist at Lenox Hill Hospital who was not involved with the study, told USA Today. “We know that soluble is most helpful in improving colon transit times. As the contents of the colon move at a better rate, there is thought to be less toxic exposure to the interior of the colon thereby reducing risk of developing colon cancer.” The findings, which appeared in the Archives of Internal Medicine, found that people who ate the most fiber in the study had a 22 percent lower risk of death than people who ate the least fiber.

The evidence was weaker for fiber from fruits, vegetables, and legumes, says study researcher Dagfinn Aune. “It doesn't mean you shouldn't eat your fruits and vegetables," he said. He found fewer studies on the impact on colon cancer risk of fiber from fruits, vegetables, and legumes than studies looking at the other foods, he says. “It's possible that we did not have enough statistical power.” He added that the study looked only at the effect of fiber.

A government study earlier this year suggested that the more fiber a person eats, the longer they will live, the Associated Press reported. That's because of a lowered risk of death from heart, respiratory and infectious disease for men and women, as well as a lowered risk of dying from cancer for men.

The findings provide more evidence of the many health benefits of whole grains, but further research is needed to learn how this occurs, Anne Tjonneland, from the Danish Cancer Society, added in an accompanying editorial.

A whole-wheat bread slice has 2 grams of fiber and a cup of oatmeal has 4 grams of fiber. Americans don't usually get enough fiber each day, with most consuming about 15 grams. The recommended daily dose of fiber for women is 25 grams a day, and 38 grams a day for men. Fiber in diet also helps lower blood sugar and cholesterol and prevents constipation.

Colorectal cancer is the third most common cancer worldwide, with 1.2 million new cases diagnosed each year. More than 141,000 new cases of colorectal cancer are expected in the U.S. this year, according to the American Cancer Society.