Antibiotics overuse could increase bowel cancer risk, study finds

The overuse of antibiotics could increase a person’s risk of developing bowel cancer, the findings of a US study suggest.

Research published in medical journal Gut found extended use of antibiotics significantly increased the chance of polyp formation in the colon, a precursor of bowel cancer.

The findings add weight to emerging evidence that the type and diversity of bacteria in the gut may have a key role in the development of cancer, according to the authors of the study.

An Australian bowel cancer expert, Associate Professor Graham Newstead, the head of the colorectal unit at the Prince of Wales private hospital and director of Bowel Cancer Australia, said the research had “credence”.

“We know already that if you take antibiotics you frequently get diarrhoea,” Newstead said.

This happened because the antibiotic killed some of the normal bacteria, leading to an overgrowth of the abnormal bacteria in the gut.

But Newstead said the study did not look at the effect of antibiotics on the colon and caution must be taken.

US researchers monitored the health of more than 120,000 nurses, aged between 30 and 55, who were part of the the Nurses Health Study launched in 1976.

Between 2004 and 2010, 1,194 abnormal growths in the colon and rectum were diagnosed.

Those who had taken antibiotics for two months or more between the ages of 20 and 39 were 36% more likely to be diagnosed with an adenoma, or polyp, compared with those who had not taken antibiotics for any extended period in their 20s and 30s.

Similarly, women who had taken antibiotics for two months or more during their 40s and 50s were 69% more likely to be diagnosed with an adenoma.

And those who had taken these drugs for 15 days or more between the ages of 20 and 39, and between the ages of 40 and 59, were 73% more likely to be diagnosed with an adenoma.

“It does seem to indicate that people who have too many antibiotics might be at more risk of of getting polyps than people who have less of them,” Newstead said.

“And, remembering that not all polyps turn to cancer but the cancer comes from the polyps. If you have more polyps or tendency to get polyps then maybe you are slightly more at risk of getting cancer.”

The message to be taken from the study was not to use antibiotics for a “tickle” in the throat or a cold, Newstead said.

Antibiotics overuse could increase bowel cancer risk, study finds