Helicobacter pylori — the common stomach bacterium best known for causing ulcers and gastric cancer — is increasingly being linked to colorectal cancer (CRC) as well. But the science here is a textbook lesson in why “linked to” is not the same as “causes,” and why more evidence sometimes brings more uncertainty rather than less.
A very common infection
H. pylori is remarkably widespread, infecting roughly half the world’s population, often silently from childhood. Most people never develop symptoms, but the bacterium is a well-established cause of peptic ulcers and a recognized risk factor for stomach cancer. Because it triggers chronic inflammation in the digestive tract — and inflammation is a known driver of cancer — researchers have long wondered whether its effects might extend beyond the stomach to the colon.
What the evidence shows
A growing body of observational studies and recent meta-analyses reports an association between H. pylori infection and higher CRC risk, as well as its precursor, colon adenomas (polyps). Given how many people carry the bacterium, even a modest increase in risk would matter at a population scale. Proposed mechanisms include chronic inflammation and shifts in gut hormones and the microbial community of the gut.
Why it’s genuinely unsettled
The pivotal practical question — does eradicating H. pylori lower colon-cancer risk? — has produced conflicting answers. A 2026 population-based study found CRC incidence and mortality were lower among people who had been treated for the infection compared with the general population, hinting at a protective effect. Yet a large Swedish nationwide cohort found the opposite signal: eradication was associated with an elevated risk of colorectal adenocarcinoma. When high-quality studies point in opposite directions, and randomized controlled trials are scarce, a causal link simply cannot be established either way.
Why it matters
H. pylori testing and eradication are already routine for stomach-related reasons, so it’s tempting to assume treating it might also protect the colon — but the current evidence does not support treating the bacterium specifically to prevent colorectal cancer. The honest status is a real and strengthening association alongside an unresolved treatment question. For readers, the practical takeaways are unchanged: follow standard colorectal cancer screening guidance, and address H. pylori for its established gastric reasons. This summarizes research and is not medical advice; screening decisions belong with your doctor.