Fiber and its role in cancer

Question.

Eating foods high in fiber is believed to help protect against colorectal cancer. Might fiber consumption also help those who already have this cancer?

Answer. For a recent study published online this month in JAMA Oncology, researchers analyzed data on 1,575 adults (average age, 67) who had stage 1, 2 or 3 colorectal cancer, meaning that it had not spread (metastasized) to distant sites in the body.

In the next eight years, 773 people died, including 174 people whose death was attributed to colorectal cancer. Comparing the amount of fiber in the participants' diets, those with higher consumption of fiber were less likely to have died, especially from colorectal cancer.

Among people who had increased their dietary fiber intake after their cancer diagnosis, each increase of 5 grams of fiber a day lowered their odds of dying from colorectal cancer by 18 percent and of dying from any cause by 14 percent.

Results varied somewhat by the source of the fiber, with fiber from cereal showing the strongest link to risk reduction and fiber from fruit the weakest.

Who may be affected? People with colorectal cancer that has not metastasized. Having an inflammatory bowel disease, such as Crohn's or ulcerative colitis, is a risk factor for this cancer, as is having a family history of colorectal cancer or colorectal polyps.

A low-fiber, high-fat diet is among lifestyle factors believed to contribute to the development of the cancer. Others include being inactive, being overweight, smoking and drinking alcohol. Colorectal cancer, the second-leading cause of death from cancer in the United States, is most common among people 75 and older.

Caveats: Dietary data came from the participants' responses on periodic questionnaires.