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Healthy Habits

A Bacterial Link

The microbes living in your gut may explain how diet influences colorectal cancer risk. By Lori Miller Kase

A growing body of research indicates that a healthy diet—rich in vegetables, fruits, whole grains and fiber—may help reduce the risk of developing certain types of colorectal cancer. A study published in the July 2017 issue of JAMA Oncology suggests that diet may influence colorectal cancer risk by affecting the bacteria in the gut.

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​The study tracked the diets of more than 137,000 people enrolled in the ongoing Nurses’ Health Study and Health Professionals Follow-up Study. During 2​6 to 32 years of follow-up, 3,260 people developed colorectal cancer. Researchers were able to analyze the microbial content of the tumors of 1,019 of these participants.

People following a diet rich in whole grains, fiber, fruits and vegetables, referred to as a prudent diet, had a reduced risk of developing colorectal tumors containing Fusobacterium nucleatum, a bacterium that has been linked to both inflammatory bowel disease and colon cancer.

​PHOTO © artisteer / istock​
Fiber content appeared to play a role in the beneficial effects of the prudent diet. Compared to subjects with the least fiber-rich diets, those with the most fiber in their diets were half as likely to develop F. nucleatum-positive tumors. “That’s a big effect in epidemiology,” says Shuji Ogino, a pathologist and epidemiologist at the Dana-Farber Cancer Institute in Boston and the study’s co-senior author. Fiber may encourage the growth of beneficial bacteria, while suppressing that of F. nucleatum.

The researchers found little evidence that diet affects the risk of developing F. nucleatum-negative colorectal cancer.
“This is the first large, well-designed human study to link diet, the gut bacteria and colon cancer,” says Jiyoung Ahn, a molecular epidemiologist at the NYU Perlmutter Cancer Center in New York City, who identified an association between Fusobacterium and colon cancer in a 2013 study. The new study, she adds, “helped to contribute to a better understanding of the diet and colon cancer relationship.” ​​


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