Why Doctors Think Colon Cancer Is on the Rise in Gen Z and Millennials

Generation Z and millennials are known for prioritizing their physical and mental health. However, that doesn’t make them invincible when it comes to a certain type of cancer.

In the United States, the number of cases of colorectal cancer (CRC) has nearly doubled in younger adults—especially those between the ages of 20 and 49—since the early 1990s.

A 2022 study published by the National Library of Medicine revealed the rate of CRC has increased from 8.6 cases per 100,000 people in 1992 to 12.9 cases per 100,000 in 2018, with the biggest rise seen in those aged 40-49. While CRC death rates have been dropping in older adults, they have remained unchanged at 2.8 per 100,000 in younger adults.

While medical professionals cannot pinpoint one specific cause, there are many factors that may increase the likelihood of being diagnosed with CRC. Newsweek spoke to three doctors about the rising rates of CRC in young people and the lifestyle changes that can help prevent it.

Why Is Colorectal Cancer on the Rise Among Young Adults?

Tim Spector, a British epidemiologist, medical doctor, and scientific co-founder of ZOE, a health science company specializing in personalized nutrition, spoke to Newsweek about the diets of Gen Z and millennials.

“It seems that younger generations want to eat well. However, because ‘wellness’ has become fashionable, there’s a great deal of misinformation on social media. This can make it difficult for people of any age to know how to eat healthily,” he said.

Researchers have discovered that consuming large amounts of ultra-processed foods (UPF) raises the risk of several types of cancer, including colorectal, breast, and pancreatic cancers. Candy, fast food, and sugary drinks may instantly spring to mind when thinking of this food group, but there are products marketed as “healthy” that are heavily processed and contain artificial ingredients, such as protein bars, granola, and vegan “meats.”

The American diet can be characterized by insufficient fruits and vegetables, reliance on refined grains, consumption of fatty protein sources like fried foods and bacon, sugary drinks instead of water, and excessive processed foods high in sugar, fat, and sodium.

“We know that high fiber diets can help reduce risk for colorectal cancer but unfortunately the American diet is typically low in fiber,” Dr. Anne K. Mongiu, a colon and rectal surgeon in New Haven, Connecticut, told Newsweek. “It includes multiple types of foods that we know can increase cancer risk such as red meat and processed foods.

“This kind of diet tends to promote obesity and issues with metabolism. There are multiple things that change when a person is obese and/or has metabolic syndrome. These conditions can change the environment within the body and lead to things like chronic inflammation, development and growth of cancers by affecting certain cells and increasing levels of hormones like leptin and adiponectin.”

She added: “The high-fat content of this diet can activate certain pathways in the body that stimulate basic cell types (stem cells) that line the large intestine and trigger them to turn cancerous.”

Can Certain Foods or Diets Help Protect Against Colorectal Cancer?

Spector emphasized the importance of a fiber-rich foods like fruits, vegetables, whole grains, legumes, nuts and healthy fats found in nuts, seeds, and oily fish.

“When it comes to protecting against colorectal cancer, it’s not just about avoiding the bad stuff—it’s also about doubling down on what actively helps your body thrive,” he said. “Fiber does far more than just help with digestion; it regulates bowel movements and reduces the time harmful substances are in contact with the colon. That’s crucial, because anything that lowers the odds of toxins building up in the gut is going to help reduce cancer risk. Think of fiber as a kind of cleanup crew for your colon.”

Fiber is the main fuel for gut microbes, helping them produce beneficial chemicals that support overall health, not just in the gut, and is crucial for maintaining a healthy gut barrier and immune system communication.

“It’s not enough to simply eat ‘healthy’—you need to eat in a way that supports a healthy, balanced gut microbiome. This is where fermented foods really shine,” Spector said.

Fermented foods are beneficial for gut health as they contain probiotics—live bacteria that help balance the gut microbiome. These include yogurts, Kefir, and Kimchi.

Spector emphasizes the importance of healthy fats, which help reduce inflammation—a key factor in CRC. He advises creating a diet that is anti-inflammatory, microbiome-friendly, and high in fiber, while avoiding ultra-processed foods that contribute to chronic inflammation.

But food isn’t solely to blame, there are other factors that cause CRC such as family history, smoking, heavy alcohol use and environment.

Pollutants Disrupt the Balance of Bacteria in Our Gut

Dr. Michelle Hughes, a gastroenterologist at Yale Medicine, told Newsweek about the exposure to environmental factors like natural or human-made chemicals that may mimic, block, or interfere with the body’s hormones, called Endocrine-disrupting chemicals (EDCs).

“EDCs are small airborne particles and chemical pollutants is thought to be a significant contributor. These pollutants can disturb the healthy balance of bacteria in our intestines, causing inflammation and stress that can lead to cancer. Another factor is what’s known as the ‘birth cohort effect,'” she said. “This means that people born after 1950 might be more at risk because they have been exposed to more environmental changes and pollutants throughout their lives.”

Diagnosis in Younger Adults Is Often Delayed

Mongiu, who is affiliated with Yale New Haven Hospital, explained to Newsweek that CRC doesn’t discriminate and can affect people of all ages.

“I have seen a rise in early onset colorectal cancer with patients presenting as early as their mid-20s, often with advanced disease,” she said.

Mongiu continued: “Younger adults experience the same warning signs as older individuals, but the diagnosis can often be delayed due to the false perception that young people are less likely to have this disease.”

The symptoms include change of bowel habits, blood in stool, tiredness and abdominal pain. Mongiu said that symptoms are often mistaken for a “less serious” condition such as irritable bowel syndrome (IBS). She urges all age groups to recognize the warning signs and seek prompt medical attention.

“Early detection can improve treatment outcomes, especially in younger adults who might not typically be considered at risk for colorectal cancer,” she said.

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