Your gut is a microbiome that plays host to trillions of bacteria, including many species that are still unknown.

These intestinal floras influence health through their roles in digestion, inflammation, and immunity, and new research shows that they may play a role in the development of colon cancer as well.

A study published in the Journal of the National Cancer Institute finds that people who have a less diverse population of bacteria in their gastrointestinal tracts may be at greater risk of getting colorectal cancer.

“Samples from people who had colon cancer had less bacterial diversity compared with samples from healthy individuals.”

In the study, researchers analyzed stool samples from 47 individuals newly diagnosed with colorectal cancer and compared them with samples from 94 healthy adults who did not have cancer. By examining bacterial DNA, they compared the respective samples’ intestinal microbes.

After controlling for disease risk factors including age, gender, body mass index, race, and smoking, results showed that fecal samples from people who had colon cancer had less bacterial diversity compared with samples from healthy individuals.

The researchers looked at the specific types of bacteria found in the stool samples. They discovered that colon cancer patients had higher levels of Fusobacterium and Porphyromanas, bacteria that appear to promote inflammation in the gut and mouth, which can fuel cancer growth.

In addition, study subjects tended to have lower levels of two “good” microorganisms that may prevent the development of colon cancer – Clostridia, bacteria that help break down dietary fiber and carbohydrates and butyrate, a short-chain fatty acid produced by probiotic bacteria that prevent inflammation in the colon.

This reduced bacterial diversity may indicate an imbalance in the intestinal ecosystem. Possible triggers include obesity and diet, with an emphasis on fiber-rich food (fruits, vegetables, legumes, etc.) intake levels.

However, study authors note that the results only show an association between these factors, not conclusive evidence that differences in bacteria levels cause colon cancer.

"It will take more research to determine if this decreased diversity leads to colon cancer or is a response to having the disease,” says lead study author Jiyoung Ahn, assistant professor of epidemiology at the New York University School of Medicine in New York.

Further research may uncover new approaches to protecting against this serious disease, she says, including ways to alter gut bacteria to promote health.

The Bottom Line

According to the American Cancer Society, colon cancer claims 50,000 lives every year and is the second-leading cause of cancer deaths. These are daunting figures, and yet colon cancer isn’t the only illness intestinal bacteria have been linked to.

This study comes on the heels of another study that links intestinal bacteria to rheumatoid arthritis. Research showed that patients newly diagnosed with the condition had higher levels of the bacteria P. copri than healthy individuals or patients who were undergoing treatment for a chronic condition. Here, too, overabundance of this bacterium was associated with increased inflammation and lower levels of beneficial bacteria.

And yet another recent study showed that the number and kinds of bacteria, and even bacterial function, can change within a day of switching from a normal diet to one that is exclusively plant or animal-based. Animal-based diets stimulated the growth of 22 species of bacteria including those good at resisting bile acids, fluids produced by the body to help digest fats. These bacteria promote inflammation and are linked to colitis. By contrast, plant-based diets increased levels of three bacterial species, including one believed to be sensitive to fiber intake.

The bottom line is that each day, we’re learning more and more about how our microbiome – the bacterial community and its genes in each person’s gut – influences our health and wellness. This learning offers new and promising ways to deal with health issues as diverse as acne and obesity to colorectal cancer and rheumatoid arthritis.

While we tease out this information, you should be aware of the risk factors for colorectal cancer, which include:

• older age
• race
• inflammatory intestinal conditions
• family history of this condition
• eating a low-fiber, high-fat diet
• having a sedentary lifestyle
• diabetes
• obesity
• smoking
• heavy alcohol use

Reduce your risk by doing the following:

• minimize intake of red meat, and in particular, processed meats
• eat a wide variety of fruits and vegetables, especially dark, leafy greens and cruciferous vegetables (broccoli, cauliflower, etc.), and whole-grain foods high in fiber
• engage in regular physical activity
• watch your weight
• consume alcohol in moderation
• quit smoking

Your gut health can influence and be influenced by your overall health, so maximize your wellness and minimize your risk of developing this and other debilitating diseases.