Eating More Fiber Tied to Lower Mortality With Colon Cancer
By Lisa Rapaport
(Reuters Health) - People who eat a high-fiber diet or increase their fiber intake after a colon cancer diagnosis may be less likely to die of these tumors than individuals who don’t consume much fiber, a recent study suggests.
“Eating more fiber 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 fiber eaten before diagnosis,” Chan said by email.
Chan and colleagues studied 1,575 adults with colon cancer who completed diet surveys detailing how much fiber they ate. They followed half of the participants for at least 8 years. During that period, 773 people died, including 174 who died of colorectal tumors.
High fiber diets were associated with lower mortality. Compared to the lowest fiber intakes in the study, each additional five grams of fiber intake was associated with 22% lower odds of death from colorectal cancer during the study, as well as 14% lower mortality from all causes of death, researchers reported November 2 in JAMA Oncology.
Changing the diet after the diagnosis to add more fiber was also linked with survival benefits. Each additional five grams of fiber people added to their diets after a colorectal cancer diagnosis was associated with 18% lower odds of death from colorectal cancer during the study, as well as 14% lower mortality from all causes of death.
The type of fiber mattered, however.
“It appears that cereal fiber 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 fiber was linked to 33% lower odds of death from colorectal cancer and 22% lower odds of mortality from all causes, the study found.
Vegetable fiber wasn’t linked to a meaningful reduction in deaths from colon cancer, but each extra 5 grams a day was associated with 17% lower chances of death from all causes.
Fruit fiber, 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 fiber 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 in Ann Arbor who wasn’t involved in the study.
It’s possible that fiber may have beneficial effects on metabolism that may protect against cancer, Hendren added by email, but it’s not clear why patients who already have colorectal tumors would live longer by eating more fiber.
JAMA Oncology 2017.
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