A widely occurring stomach bacterium could be associated with as many as one in five bowel cancer cases globally, new research indicates. In a large international analysis drawing on health data from 48 million people, scientists found that exposure to Helicobacter pylori, commonly known as H. pylori, was linked to a 1.59 times higher risk of developing bowel cancer.
H. pylori infections often go unnoticed, with many people experiencing no symptoms at all. However, in some cases, the bacteria can trigger stomach ulcers or inflammation of the stomach lining. In the UK, it is estimated that up to 40% of people may carry H. pylori in their stomach. The infection can spread through contact with an infected person’s saliva, vomit or faeces.
The bacterium is already recognised as a cause of stomach cancer, but its possible role in bowel cancer has long been debated. Researchers said the connection between H. pylori and colorectal cancer remains “highly controversial,” prompting them to take a closer look at the evidence.
The study was led by experts from the University of Hong Kong and the University of California San Diego, who reviewed and analysed findings from 43 previously published studies.
Writing in the journal eGastroenterology, the researchers said: “H. pylori exposure may be related to an estimated 22% of global CRC (colorectal cancer) cases under a causal assumption.”
Among the studies examined, four specifically assessed whether antibiotic treatment to “eradicate” H. pylori had any effect on a person’s longer-term risk of cancer.
Those findings pointed to a possible reduction in bowel cancer risk after the infection was cleared, although the benefit appeared to emerge only after a period of around 10 years.
The analysis also suggested that the share of bowel cancer cases potentially connected to H. pylori exposure appeared to increase in more recent birth decades, particularly among those born in the 1960s and 1970s.
The researchers noted that many other factors play a role in bowel cancer risk, including genetics, age, lifestyle and diet.
When H. Pylori causes gastritis, symptoms include belly pain, feeling sick, belly bloating and burping.
It is typically treated with a combination of medication to reduce the amount of acid in the stomach and antibiotics.
