Key TakeawaysColorectal cancer is on the rise in people younger than 50, despite a decline in colorectal cancer diagnoses in the general population.Researchers are working to understand how the trillions of microbes in the gut impact the development and progression of colorectal cancer.Diet, environment, and certain medications can affect your gut microbiome, which may relate to cancer risk.

Key Takeaways

Colorectal cancer is on the rise in people younger than 50, despite a decline in colorectal cancer diagnoses in the general population.Researchers are working to understand how the trillions of microbes in the gut impact the development and progression of colorectal cancer.Diet, environment, and certain medications can affect your gut microbiome, which may relate to cancer risk.

When the actor Chadwick Boseman died of colon cancer at the age of 43, it shocked many to find out that colon cancer can affect someone so young.

Colon cancer is one of the fastest-growing cancer types in people younger than 50.Between 1995 and 2019, newly diagnosed cases of colorectal cancer in people who were younger than 55 have almost doubled, from 11% to 20%.

This uptick is partially due to increased awareness and improved screening efforts.But one possible pathway that may influence colorectal cancer risk is the bacteria in your gut.

What you eat, what medicines you take, and how often you exercise can all change your gut microbiome, which could be linked to cancer development down the line, according to Kimmie Ng, MD, director of the Young-Onset Colorectal Cancer Center at the Dana-Farber Cancer Institute.

However, research on the microbiome and cancer risk is still in its infancy, Ng said, and many more studies are needed to understand this possible connection better.

Adults aged between 20 and 39 had the steepest increase in distant-stage colorectal cancer occurrence from 2000 to 2016, according to a study published last year.Distant-stage, ormetastatic, means the cancer has spread to other parts of the body.

Why Does Gut Health Matter?

Several factors might be driving this trend, and the microbiome’s involvement is just one theory to explain the increase, according toRabia de Latour, MD, a gastroenterologist at NYU Grossman School of Medicine.

The “microbiome” refers to the trillions of microorganisms—bacteria, viruses, and fungi—living in the body. Most of these microbes live in your intestines, where they play a role in digestion and possibly other biological processes. Some microbes are helpful to the body, while others can be harmful.

Scientists know much more about what can go wrong in the microbiome than what a healthy microbiome should look like. Taking antibiotics, having an infection, or changing your diet can all cause this phenomenon called “dysbiosis”—an imbalance or unfavorable shift in the microbiome. This can change either the diversity of species or the amounts of specific microbes in your gut, hence harming your digestive function and overall health.

The microbiome is somewhat of a new frontier in medicine, and even the top experts in the field have a lot to learn about how the balance of bacteria in the gut may affect cancer development.

Researchers at the Dana Farber Cancer Institute are currently conducting a large prospective study to further investigate the role of the microbiome in young-onset colorectal cancer, according to Ng, and several other studies of the microbiome are underway.

Dysbiosis: Overview and Treatment

How May the Gut Microbiome Affect Cancer Risk?

An increasing number of studies have considered the role of the gut microbiome in colorectal cancer progression.

Normally, “good bacteria” in the gut act as a barrier to harmful microbes that can cause disease or inflammation. When there’s an imbalance in the gut microbiome—particularly a reduction in helpful microbes—inflammation can occur. This kind of inflammation and imbalance has been seen in association with type 2 diabetes, obesity, and inflammatory bowel disease.

Long-term or chronic inflammation in any part of the body can increase the chances that normal cells will mutate to become cancerous, de Latour explained. Researchers have theorized that dysbiosis in the gut can lead to inflammation that increases cancer risk, but they have yet to prove this process in scientific studies.

In research, scientists have identified specific strains of bacteria present in fecal samples from people with colorectal cancer. One study found that a species called “Flavonifractor plautii”—a bacteria that helps to break down some plant foods—was the dominant bacterium in people with young-onset colorectal cancer’sstool.

The bacteria speciesFusobacterium nucleatumandpks+ Escherichia colihave also been linked to colorectal cancer, Ng said. In the study of fecal samples,Fusobacteriumwas also identified as an important bacterium for colorectal cancer progression both in young-onset cases and in people over 50 with colorectal cancer.E. coli, a bacterium commonly implicated in food poisoning,can carry a marker called “pks,” which is linked to colorectal cancer development.

It’s also important to considerracial disparitiesin colorectal cancer risks: Black and Hispanic Americans are more likely to be diagnosed with early-onset colorectal cancer that has already progressed to advanced stages.

How Can You Better Take Care of Your Gut?

The makeup of your microbiome may also affect how you respond to cancer treatments such asimmunotherapy, Ng said, although research has focused on other cancer types.

While some aspects of the microbiome don’t change much after the first few years of life, the balance of bacteria in your gut constantly shifts as you eat and move through the world. Taking antibiotics can impact your gut microbiome, asantibioticsaffect both good and bad bacteria growth.Your microbiome even looks slightly different after a bowel movement, de Latour said.

In general, Ng said that the diet and lifestyle behaviors recommended for colorectal cancer prevention also likely result in improved gut health. This includes not smoking or drinking alcohol, minimizing red meat intake, exercising, and maintaining a healthy body weight.

Best and Worst Foods for Gut Health

What This Means For YouMaintaining a healthy and diverse microbiome may be a facet of cancer prevention in the near future. Keep this in mind as you feed the helpful and harmful bacteria in your gut.

What This Means For You

Maintaining a healthy and diverse microbiome may be a facet of cancer prevention in the near future. Keep this in mind as you feed the helpful and harmful bacteria in your gut.

10 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Koh B, Tan DJH, Ng CH, et al.Patterns in cancer incidence among people younger than 50 years in the US, 2010 to 2019.JAMA Netw Open. 2023;6(8):e2328171. doi:10.1001/jamanetworkopen.2023.28171

Siegel RL, Wagle NS, Cercek A, Smith RA, Jemal A.Colorectal cancer statistics, 2023.CA A Cancer J Clinicians. 2023;73(3):233-254. doi: 10.3322/caac.21772

Done JZ, Fang SH.Young-onset colorectal cancer: A review.World J Gastrointest Oncol. 2021;13(8):856-866. doi:10.4251/wjgo.v13.i8.856.

Montminy EM, Zhou M, Maniscalco L, et al.Shifts in the proportion of distant stage early-onset colorectal adenocarcinoma in the United States.Cancer Epidemiol Biomarkers Prev. 2022;31(2):334-341. doi:10.1158/1055-9965.EPI-21-0611

Dunn AB, Jordan S, Baker BJ, Carlson NS.The maternal infant microbiome: considerations for labor and birth.MCN Am J Matern Child Nurs. 2017;42(6):318-325. doi:10.1097/NMC.0000000000000373

Gritz EC, Bhandari V.The human neonatal gut microbiome: a brief review.Front Pediatr. 2015;3:17. doi:10.3389/fped.2015.00017

Al Bander Z, Nitert MD, Mousa A, Naderpoor N.The gut microbiota and inflammation: an overview.Int J Environ Res Public Health. 2020;17(20):7618. doi:10.3390/ijerph17207618

Yang Y, Du L, Shi D, et al.Dysbiosis of human gut microbiome in young-onset colorectal cancer.Nat Commun. 2021;12(1):6757. doi:10.1038/s41467-021-27112-y

Ramirez J, Guarner F, Bustos Fernandez L, Maruy A, Sdepanian VL, Cohen H.Antibiotics as major disruptors of gut microbiota.Front Cell Infect Microbiol. 2020;10:572912. doi:10.3389/fcimb.2020.572912

Meet Our Medical Expert Board

Share Feedback

Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit

Was this page helpful?

Thanks for your feedback!

What is your feedback?OtherHelpfulReport an ErrorSubmit

What is your feedback?