bacteria and colorectal cancer risk

A recent clinical study investigated the link between diet, gut bacteria and colorectal cancer risk. A prudent diet low in fats, cholesterol, and sodium was associated with a lower risk of developing colorectal cancer, particularly the type associated with the presence of gut bacteria Fusobacterium nucleatum, compared to a Western diet.

 

Colorectal cancer is characterized by a malignant tumor found in the colon or rectum that has the potential to spread to other parts of the body. It is the second leading cause of death from cancer in men and the third leading cause in women. According to a recent systematic meta-analysis, a prudent diet rich in fruits, vegetables, and whole grains has been associated with a lower colorectal cancer risk. On the other hand, a Western diet rich in red and processed meats has been associated with colorectal carcinogenesis. While the link between diet and cancer risk has been well documented, how diet can influence the development of colorectal tumors remains unclear. Interestingly, a type of bacteria in the gut, known as Fusobacterium nucleatum (F. nucleatum), has been shown to contribute to the development of colorectal cancer by limiting the ability of the host’s immune response to kill the tumor cells. A higher amount of F. nucleatum has even been linked to shorter survival time in cancer patients. Researchers are interested in the role of these gut bacteria in the link between diet and colorectal cancer; this relationship remains unclear because F. nucleatum is not found in all colorectal cancers.

In this study, Mehta and the team of researchers at the Clinical and Translational Epidemiology Unit in Boston sought to determine if the association between diet and colorectal cancer risk is dependent on the presence of F. nucleatum in the tumor tissue. Data from two ongoing prospective cohort studies, the Nurses’ Health Study (NHS) and the Health Professional Follow-up Study (HPFS), were used. Of the total individuals considered for the study, 47 449 men aged 40 to 75 years old and 86 768 women aged 30 to 55 years old were included in their analysis. Participants reported food intake and incidence of colorectal cancer, and researchers assessed the presence of F. nucleatum in cases with available colorectal tissue data.

The study, published in JAMA Oncology, found that the association between a prudent diet and colorectal cancer differs depending on the presence of F. nucleatum in the cancerous tissue. Those who followed a prudent diet had a significantly lower chance of developing F. nucleatum-positive colorectal cancer but not F. nucleatum-negative colorectal cancer. Individuals who followed a prudent diet had the same chances of development F. nucleatum-negative colorectal cancer compared to those who followed a western diet. This suggests that diet is related to colorectal cancer risk, but only when F. nucleatum plays a role.

This study reiterates the importance of diet in modulating cancer risk, and indicates that the cancer preventative effects of diet are likely mediated through the bacteria colonizing the gut.

 

Written By: Danielle Vitali, BSc



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