Long-term use of antibiotics during adulthood increases the likelihood of developing precancerous intestinal abnormalities. This is the conclusion of a study carried out by researchers from Massachusetts General Hospital and Harvard Medical School in Boston (USA) that reflects an increased risk of adenoma incidence.
The connection between antibiotics and bowel cancer is due to the effect of antibiotics on intestinal bacteria (the microbiome); altering the numbers and types of bacteria present in the intestine, triggering pathologies.
To investigate this, the experts examined data from the Nurses Health Study, a project that has analyzed 121,700 American nurses since 1976. The women were between 30 and 55 years old when the study began. Every 2 years, participants filled out detailed questionnaires with general demographic information, lifestyle factors (such as smoking and exercise), medical history, and disease development. Every 4 years, they also completed a questionnaire about their eating habits.
Using data from 16,642 women in this sample, aged 60 and over in 2004, scientists found that 1,195 adenomas (polyps: benign tumors that precede most cases of bowel cancer) had been diagnosed.
After analyzing all the documentation, the experts observed that the long-term use of antibiotics had a direct relationship with the adenoma if it had been consumed at younger ages. Thus, women who had taken antibiotics for 2 months when they were 20 or 30 years were 36% more likely to be diagnosed with adenoma and n compared with those who had not taken antibiotics for many consecutive weeks.
Additionally, women who took antibiotics for two months or more during their 40s and 50s were 69% more likely to be diagnosed with an adenoma compared to those who had not taken these drugs for a long period of time.
Although this is an observational study and more studies will be needed to confirm this finding, the scientists suggest that there is a biological explanation for these associations, which is that antibiotics significantly alter the gut microbiome by reducing the diversity and number of bacteria.
“The findings, if confirmed by other studies, suggest the potential need to limit the use of antibiotics and sources of inflammation that can lead to tumor formation,” the authors state.
The study has been published in the journal Gut.
