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Connection Between Gut, Diet, and Colorectal Cancer

Wednesday, May 17, 2017

The lead authors at Dana-Farber Cancer Institute and Massachusetts General Hospital report that a new study has provided some of the strongest evidence yet that microorganisms in the large intestine can serve as a link between diet and certain types of colorectal cancer.

The online publication in JAMA Oncology, focuses on one of the hundreds of types of bacteria in the large intestines, Fusobacterium nucleatum, which is thought to play a part in colorectal cancer. The researchers tracked the diets of more than 137,000 people for decades and examined over 1,000 colorectal tumor samples for this bacteria. They determined that people with a ‘prudent’ diet which is rich in whole grains and fiber had a lower risk of developing colorectal cancer containing F nucleatum, however their risk of colorectal cancer that lacked that bacteria was unchanged.

Having a prudent diet appears to protect oneself from colorectal cancer. This study suggests that healthy foods may achieve these benefits, in part, by altering the amounts of the microorganisms in the digestive tract, such as the F nucleatum.

"Though our research dealt with only one type of bacteria, it points to a much broader phenomenon—that intestinal bacteria can act in concert with diet to reduce or increase the risk of certain types of colorectal cancer," says Shuji Ogino, MD, PhD, of Dana-Farber, Harvard T.H. Chan School of Public Health, and Brigham and Women's Hospital, the cosenior author of the study with Charles Fuchs, MD, MPH, director of the Gastrointestinal Cancer Center at Dana-Farber and Brigham and Women's, and Andrew Chan, MD, MPH, of Massachusetts General Hospital, Brigham and Women's, and the Broad Institute of Massachusetts Institute of Technology and Harvard.

Chan adds that “These data are among the first in humans that show a connection between long-term dietary intake and the bacteria in tumor tissue. This supports earlier studies that show some gut bacteria can directly cause the development of cancers in animals.”

This research was drawn from dietary records of 137,217 people in the Nurses' Health Study and Health Professionals Follow-up Study, large-scale health tracking studies, some of which had developed colon or rectal cancer over decades. The researchers measured the levels of F nucleatum in the patients' tumor tissue and blended the data with information of diet and cancer incidence.

Ogino remarks “Recent experiments have suggested that F nucleatum may contribute to the development of colorectal cancer by interfering with the immune system and activating growth pathways in colon cells.” He adds "One study showed that F nucleatum in the stool increased markedly after participants switched from a prudent to a Western-style, low-fiber diet. We theorized that the link between a prudent diet and reduced colorectal cancer risk would be more evident for tumors enriched with F nucleatum than for those without it."

And that is exactly what the study shows, participants who followed a prudent diet had a lower risk of developing colorectal cancer laden with F nucleatum. However, they did not receive extra protection against colorectal cancers which did not contain the bacteria.

"Our findings offer compelling evidence of the ability of diet to influence the risk of developing certain types of colorectal cancer by affecting the bacteria within the digestive tract," Ogino says.

"The results of this study underscore the need for additional studies that explore the complex interrelationship between what someone eats, the microorganisms in their gut, and the development of cancer," Chan says.

Reference: Dana-Farber Cancer Institute