Cancer was once considered a disease of aging, primarily affecting people over 60 or 70. While it’s still true that most new cancer cases occur in those over 70, the pattern is shifting in subtle ways. Some cancers are now appearing more frequently in younger individuals.
Consider colorectal (bowel) cancer: while rates have dropped in people over 60, data reveals a sharp rise in many developed countries among those under 50—a trend known as early-onset disease. This increase isn’t simply due to better screening or diagnosis, nor is it limited to one country or community. It’s a real, global phenomenon, with cases jumping from about 94,700 in 1990 to 225,736 in 2019. A European study found that between 2004 and 2016, incidence rose by 7.9% per year in people aged 20–29, 4.9% in those 30–39, and 1.6% in the 40–49 age group. Not only is colon cancer increasing in every age group under 50, but the rise is fastest among the youngest. Projections suggest that early-onset colorectal cancer could double every 15 years in Australia, Canada, the UK, and the US.
In England, the NHS bowel cancer screening program invites people aged 50–74 for free screening every two years. However, this leaves out younger individuals, who are often diagnosed only at a late stage when the cancer has spread and symptoms appear.
What’s driving this increase in young people? Genetics isn’t the main cause—about 75% of cases occur in people with no family history or known genetic predisposition. Scientists are instead looking at environmental factors that have changed since the 1960s, with each generation facing a higher cancer risk than the last.
One factor consistently stands out: ultra-processed foods. A 2025 review in Nature Reviews Endocrinology highlighted the connection. These foods—broadly defined as factory-packaged snacks, ready meals, sugary cereals, soft drinks, processed meats, and many fast foods—now make up over half of the average diet in countries like the UK and US.
Evidence is mounting: a major study in the British Medical Journal examined three large US groups to explore the link between ultra-processed foods and colorectal cancer risk. One group included more than 46,000 men tracked for 24 to 28 years. Compared to those who ate the least ultra-processed food, those who consumed the most had a 29% higher risk of developing colorectal cancer—even after accounting for nutrition and weight. The authors note that more research is needed to understand exactly how these foods contribute to cancer development.
Interestingly, while much research ties ultra-processed foods to rising obesity—a major risk factor for many cancers—the study above points to increased colorectal cancer even in people of normal weight. Could these foods be carcinogenic regardless of a person’s BMI? In other words, are they harmful even for those who are active and maintain a healthy weight?
Diets high in ultra-processed foods have been linked to disrupted insulin signaling, chronic low-grade inflammation, and changes in gut bacteria—all factors involved in cancer development. What we eat influences cell growth, immune function, and the behavior of gut microbes, which help regulate inflammation and immunity. Animal studies show that emulsifiers, additives, and artificial sweeteners common in ultra-processed foods can promote gut inflammation and tumor growth. At the same time, the lack of fiber and protective plant compounds in these foods can alter the gut microbiome, which is essential for the body to function at its best.Skip past newsletter promotion
Sign up for Matters of Opinion
Free weekly newsletter
Guardian columnists and writers share what they’ve been debating, thinking about, reading, and more.
Enter your email address
Sign up
Privacy Notice: Newsletters may include information about charities, online ads, and content funded by external parties. If you don’t have an account, we’ll create a guest account for you on theguardian.com to send this newsletter. You can complete full registration anytime. For more details on how we handle your data, see our Privacy Policy. We use Google reCaptcha to protect our website, and the Google Privacy Policy and Terms of Service apply.
After newsletter promotion
Ultra-processed foods: 19 essential facts
Read more
It took decades, but we now recognize that tobacco causes lung cancer and alcohol increases the risk of breast and liver cancer. In the coming years, ultra-processed foods may be identified as a major risk factor for colorectal cancer, especially in young adults. I’m not saying this to alarm you, but to highlight findings from recent, thorough long-term studies. What we eat has a greater impact than many realize.
If smoking was the cancer culprit of the 20th century, ultra-processed foods could be its equivalent in the 21st. While the science isn’t definitive yet, evidence is mounting quickly. It’s often said that food is medicine, and we’re learning more and more that food is prevention. For example, a 2025 study found that regularly eating yogurt may lower the risk of colon cancer, a type of colorectal cancer. So, if there’s one thing to remember from this: eat more yogurt and less ultra-processed food.
Prof Devi Sridhar is chair of global public health at the University of Edinburgh
Frequently Asked Questions
Of course Here is a list of FAQs about the rising rates of colon cancer in young adults designed to be clear helpful and easy to understand
BeginnerLevel Questions
1 Is it true that more young people are getting colon cancer
Yes thats correct While colon cancer is still more common in older adults studies show that the number of people under 50 being diagnosed is increasing significantly each year
2 What is the key factor that might be to blame
While the exact cause is still being researched a leading theory points to major changes in our diet and lifestyle This includes diets high in processed foods red meat and sugar and low in fiber combined with factors like obesity lack of physical activity and changes in our gut bacteria
3 What are the most common symptoms to watch for
Dont ignore persistent changes in your bowel habits such as
Diarrhea constipation or narrowing of the stool that lasts for more than a few days
Rectal bleeding or blood in your stool
Persistent abdominal cramps gas or pain
A feeling that your bowel doesnt empty completely
Unexplained weight loss
4 Im in my 30s and have a symptom Should I be worried
You shouldnt panic but you should not ignore it either See a doctor if you have any persistent or concerning symptoms Be proactive and persistent in discussing your concerns as some doctors may initially dismiss symptoms in younger patients
5 When should the average person start getting screened
The recommended age for averagerisk individuals to start screening is now 45 If you have a family history of colon cancer or other risk factors you may need to start much earlier Always talk to your doctor about whats right for you
Advanced Practical Questions
6 Beyond diet what other factors might be contributing to this rise
Researchers are also looking at other potential contributors including
The Gut Microbiome An imbalance in the trillions of bacteria in our digestive system possibly caused by modern diets and antibiotics
Environmental Factors Exposure to certain chemicals and pollutants
