Fibre-rich diet reduces mortality risk in colon cancer patients

People who eat a high-fibre diet or increase their fibre intake after a colon cancer diagnosis may be less likely to die of such tumours than those who do not eat much fibre, according to a new study.

“Eating more fibre after colorectal cancer diagnosis is associated with a lower risk of dying from colorectal cancer,” said senior study author Dr. Andrew Chan of Harvard Medical School and Massachusetts General Hospital in Boston.

“This seems to be independent of the amount of fibre eaten before diagnosis,” Chan said.

Chan and colleagues examined data on 1,575 adults diagnosed with colon cancer who completed diet surveys detailing how much fibre they ate. They followed half of the participants for at least 8 years. During that period, 773 people died, including 174 who died of colon and rectal tumours.

High fibre diets were associated with lower mortality. Compared to the lowest fibre intakes in the study, each additional five grams of fibre intake was associated with 22 percent lower odds of death from colorectal cancer during the study, as well as 14 percent lower mortality from all causes of death, researchers report.

Changing the diet after the diagnosis to add more fibre was also linked with survival benefits. Each additional five grams of fibre people added to their diets after a colorectal cancer diagnosis was associated with 18 percent lower odds of death from colorectal cancer during the study, as well as 14 percent lower mortality from all causes of death.

The type of fibre mattered, however. “It appears that cereal fibre and foods high in whole grains seem to be associated with the lowest risk of dying from colorectal cancer,” Chan said. Each additional 5 grams a day of cereal fibre was linked to 33 percent lower odds of death from colorectal cancer and 22 percent lower odds of mortality from all causes, the study found.

Vegetable fibre wasn’t linked to a meaningful reduction in deaths from colon cancer, but each extra 5 grams a day was associated with 17 percent lower chances of death from all causes.

Fruit fibre, meanwhile, didn’t appear to lower death from cancer or other causes.

The study wasn’t a controlled experiment designed to prove whether or how fibre intake might influence the odds of death from colon cancer, researchers note.

The most important risk factors for colorectal cancer are family history, personal history of polyps/cancer, certain diseases such as ulcerative colitis, and not getting screened, noted Dr. Samantha Hendren, a researcher at the University of Michigan.

“Lifestyle can also influence risk,” Hendren said. “However, diet is only one component of lifestyle risk. Not smoking, being normal weight, and taking aspirin are all associated with lower colorectal cancer risk.”

Even though diet is only one piece of the puzzle, it’s possible that fibre may have beneficial effects on metabolism that may protect against cancer, Hendren added. It’s not clear why patients who already have colorectal tumours would live longer by eating more fibre at that point, however.

“Therefore, consuming a healthy diet that is high in whole grain foods (e.g. brown rice, oatmeal, whole grain cereals or whole wheat bread) and other fibre sources such as fruits and vegetables may protect from colorectal cancer and also improves outcomes and reduces risk of death among colorectal cancer survivors,” Makarem said

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