A diet high in fiber--that's fruits, vegetables, and cereals--significantly lowers the risk of bowel cancer, according to a massive study of European eating habits by the British Medical Research Council's Dunn Human Nutrition Unit in Cambridge, England.

Involving more than a half-million people in 10 European countries, the research is the biggest study ever done on diet and cancer and showed that no matter the food source, fiber protects against bowel cancer, a disease that kills nearly 1 million people worldwide each year.

No doubt you've heard the "five a day" promotion that encourages us all to eat five servings of fruits and vegetables daily. The European study findings suggest that if you're currently eating less than that and you double the amount of fruits, vegetables, and cereals you are eating, you'll slash your risk of bowel cancer by a whopping 40 percent.

"You want loads of fruits and vegetables on your plate and whole-meal pasta and less fats and less meat," the study's lead author, Sheila Bingham, told Reuters.

And the more fiber you eat, the better. People with the lowest risk were eating five or more portions of fruit and vegetables a day plus the equivalent of five slices of whole-meal bread. In addition, previous research has shown that just two slices a day of dark bread, such as wheat, rye, and pumpernickel, as well as fiber-packed cereals significantly lowers elderly adults' risk of developing cardiovascular disease.

The European research was confirmed by U.S. researchers at the National Cancer Institute in Rockville, Md., in a study of more than 37,000 people, 3,600 of whom had non-malignant colon adenoma, which are polyps that can be precursors of bowel cancer. "In our study, high intakes of dietary fiber, especially from grains, cereals, and fruits, was associated with lower risk of colon adenoma," explained lead author Ulrike Peters in the study.