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Could Bacteria Play a Role in Colon Cancer?

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Doctor and nurse looking at colonoscopy image

The human body contains about 39 trillion bacterial cells. While most bacteria prove to be beneficial for our bodies, that’s not always the case.

Research shows certain strains of bad bacteria could play a role in the development of colon cancer. Abram Eisenstein, MD, former Cooper Clinic Gastroenterology Director, explains what the research shows and how this discovery could one day prevent colon cancer, a disease that kills more than 50,000 people in the U.S. every year.  

Bacteria Basics 

Different strains of bacteria are present in our bodies, but how do these bacteria get there in the first place? Eisenstein says it starts the day you’re born.

“What seems to happen is as you pass through the birth canal, you start acquiring bacteria in your colon,” explains Eisenstein. 

In the first several years of life, bacteria continue to accumulate and start colonizing in the colon. It’s estimated there are about 40,000 bacterial species in the human gut alone. It’s an astounding number but one Eisenstein says is meant to keep us safe. 

“These bacteria have a purpose and that’s to protect us,” says Eisenstein. “These bacteria are possibly the most powerful factor in determining not just the health of your colon, but overall health.” 

But what happens when the bacteria meant to keep us safe, doesn’t?

Bacteria Gone Bad

Most bacteria in your gut live in the colon lining, which is comprised of a mucus layer that acts as a buffer or protective covering. Normally, the bacteria don't go through that mucus barrier. In a February 2018 study, researchers found particular strains of bacteria can get through.

“These bacteria can break into this protective barrier and produce toxins,” explains Eisenstein. “This can alter the immune status of the cells in your colon, weakening them and allowing cancer to occur." 

While more research is still needed, Eisenstein says if this theory proves to be true, it could change the way colon cancer is treated and even prevented.

“If you could identify which specific bacteria species are able to break through that barrier, maybe we could develop a vaccine to kill those strains,” says Eisenstein. He says having access to that information could also allow patients to take a stool test to see if they have those species of bacteria in their bodies. 

Beneficial Bacteria

While certain “bad” strains of bacteria can play a role in the development of colon cancer, Eisenstein says “good” strains, also known as probiotics, could also prove to be beneficial in keeping cancer at bay.

“Many researchers believe we can use probiotics to help prevent colon cancer,” explains Eisenstein. “We’re at the early stages of learning how to identify good bacteria, increase their number long term and find out if it can offset the bad bacteria.”

How do these probiotics overtake the bad? That question is one researchers are still trying to answer, but one Eisenstein says science is starting to prove.

“For years, we’ve emphasized one of the best ways to prevent colon cancer is to eat more green, leafy vegetables,” says Eisenstein. “It's been proven that people who eat a plant-based diet have less cancer. Researchers think it’s because of the good bacteria.”

Eisenstein says when you eat green, leafy vegetables, your microbiome changes with more healthy bacteria than if you eat a diet containing a lot of meat or high-saturated fat. 

Why a Colonoscopy Is Key

When it comes to colon cancer detection, there are several new products available on the market. The Food and Drug Administration has approved certain at-home stool and blood tests to screen for colon cancer and polyps. The goal is to detect cancer without having to have a colonoscopy first. 

“At first you might say, ‘Eureka! This is it. I don't have to go do these tests where they put scopes in me. I'll just do a stool sample at home,’” says Eisenstein. But he says that’s where the problem lies. 

“The problem is these non invasive tests are very insensitive,” explains Eisenstein. “The tests come back positive only if you have advanced cancer.”

The tests have shown to produce false-negative results, meaning you could have colon cancer, but the test doesn't pick it up.

“Our gold standard at Cooper Clinic is to get a colonoscopy,” says Eisenstein. “For one, it's the most sensitive way of picking up early stage polyps that can cause cancer. It can also remove the polyps at the same time.”  

Eisenstein says the incidence of colon cancer in those over age 50 has decreased over the last two decades, as a result of colonoscopy screenings

“It's not just a diagnostic test, it's therapeutic,” says Eisenstein. “It can prevent colon cancer. No other test can do that.”

For more information about colonoscopy screenings or to schedule an appointment, visit