Antibiotics are a potential link to bowel cancer precursor

A new study has found that people who take antibiotics over long time are more at risk of developing growths on the bowel that could be a precursor to cancer.

The research forms part of a wider line of scientific inquiry about the effect that antibiotics and other antimicrobials have on the human digestive tract and that microorganisms that live within it. Antibiotics are designed to kill harmful bacteria but they are not precise and they kill beneficial bacteria as well. If the balance slips too far and too many beneficial bacteria are killed, this imbalance has been linked to adverse health events. The likelihood of this change to the body's microbiome is greater the longer the period of time that a course of medication is taken for. The term microbiome refers to the microorganisms living in a given ecological niche - in this case the human intestines.

Data about long-term antibiotic use and bowel growths comes from a major U.S. trial called the Nurses' Health Study, which reviewed data from 16,000 nurses. The main findings, as summarized by BBC Science, were:

Nurses who took antibiotics for two months or more, aged between of 20 and 39 years, were more likely to be diagnosed with bowel polyps (called adenomas) compared with people who had not taken long-term antibiotics

Nurses who had taken antibiotics for two months or more in their 40s and 50s were even more likely to be diagnosed with an adenoma decades later.

This led the researchers to conclude: "Antibiotics fundamentally alter the gut microbiome, by curbing the diversity and number of bacteria, and reducing the resistance to hostile bugs." This led principal scientist Yin Cao of Harvard University to tell The Tribune: "The findings, if confirmed by other studies, suggest the potential need to limit the use of antibiotics and sources of inflammation that may drive tumor formation."

While the new research, which examines cases of long-term antibiotic use with signs of growth, signals a potential link to cancer, what is being reported is bowel polyps. These are tiny growths on the lining of bowel. These growths are common and they affect around one fifth of the population. In many cases these growths do not cause any symptoms and do not become cancerous. However, some can, if untreated, become cancerous.

The research is published in the journal Gut, in a paper titled "Long-term use of antibiotics and risk of colorectal adenoma."

This is an observational study so no firm conclusions can be drawn about cause and effect. Readers should be aware that this article refers to one study and that further research is needed in this area. Any person on antibiotics should continue with their course and raise any concerns with a medical professional.

Posted by Dr. Tim Sandle