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Microorganisms living in the large intestine have been suspected as a link between diet and certain types of colorectal cancer, but now a study by HMS researchers at Dana-Farber Cancer Institute and Massachusetts General Hospital provides the strongest evidence to date that this is true.
The paper, published online on January 26 in JAMA Oncology, focuses on Fusobacterium nucleatum, one of hundreds of types of bacteria that dwell in humans’ large intestines and one thought to play a role in colorectal cancer. By tracking the diets of more than 137,000 people for decades and examining more than 1,000 colorectal tumor samples for F. nucleatum, the researchers determined that individuals following a “prudent” diet, that is, one rich in whole grains and fiber, had a lower risk of developing types of colorectal cancer containing the bacterium. Their risk for colorectal cancer types that lacked the bacterium, however, was essentially unchanged.
“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, an HMS professor of pathology at Dana-Farber, professor of epidemiology at the Harvard T.H. Chan School of Public Health, and co-senior author of the study.
The research drew on dietary records of participants in the Nurses’ Health Study and Health Professionals Follow-up Study, both large-scale health-tracking studies. Some of the participants had developed colon or rectal cancer over decades. The researchers measured the levels of F. nucleatum in the patients’ tumor tissue and merged these data with information on diet and cancer incidence.
Participants who followed a prudent diet had a lower risk of developing colorectal cancer laden with F. nucleatum. But they received no extra protection against colorectal cancers that didn’t contain the bacteria.
The authors note that the study results underscore the need for research that further explores the complex interrelationship between what someone eats, the microorganisms in their gut, and the development of cancer.
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