Why Are Colorectal Cancers Increasing in Young Adults? A New Clue From Gut Bacteria
November 12, 2025
Over the past decade, doctors across the world — including here in India — have noticed something unusual.
More and more young adults in their 20s, 30s, and 40s are being diagnosed with colorectal cancer — a disease that was once thought to affect mostly older people.
Until now, lifestyle and diet were considered the main culprits.
But a new international study has found another possible cause — something that starts much earlier in life and comes from deep inside the gut.
The Surprising Role of Certain Gut Bacteria
Researchers studying nearly 1,000 bowel cancer samples from 11 countries have identified a pattern of DNA damage linked to a toxin called colibactin.
This toxin is produced by certain strains of E. coli, a common bacterium that normally lives harmlessly in our intestines.
When these specific E. coli strains release colibactin, they can damage the DNA of colon cells — the first step towards cancer.
Interestingly, the study found that this DNA damage pattern was over three times more common in younger patients (below 40 years) compared to older ones.
Even more striking, the changes appear to happen very early in life — sometimes before age 10.
That means the “first hit” may occur in childhood, but the cancer itself develops decades later.
What Could Be Causing This Early Exposure?
Scientists believe that early-life factors — like diet, antibiotic use, mode of birth (C-section vs normal delivery), or even certain infections — might affect how these harmful bacteria settle in the gut.
It’s important to note: not all early-onset cancers are caused by this, and not all E. coli are bad.
But it’s a reminder that our gut health in childhood can have lifelong consequences.
What Can You Do to Protect Yourself and Your Family?
The Takeaway
This discovery doesn’t mean bacteria are the only reason colorectal cancers are rising in young people.
But it gives us a vital clue — and one more reason to take gut health seriously from a young age.
As we continue learning more about the gut–cancer connection, one thing remains clear:
early awareness, healthy lifestyle, and timely screening can make all the difference.
