Repeated use of some types of antibiotics may put people at increased risk of developing type 2 diabetes through potentially altering their gut bacteria, according to a large observational study.
The findings, published in the European Journal of Endocrinology, appear to reinforce public health policies to reduce unnecessary antibiotic prescriptions.
Researchers from the University of Pennsylvania looked at the number of antibiotic prescriptions given out in the UK to over 200,000 patients with diabetes at least one year before they were diagnosed with the disease.
They compared this to the number given to 800,000 patients without the condition of the same age and sex.
“We think changing levels and diversity of gut bacteria could explain the link”
The researchers found that patients prescribed at least two courses of penicillins, cephalosporines, quinolones and macrolides were at higher risk of being diagnosed with type 2 diabetes. The risk increased with the number of antibiotic courses prescribed.
Patients prescribed two to five courses of penicillins increased their risk of diabetes by 8%, while for those with more than five penicillin courses this risk increased by 23%.
For quinolones, diabetes risk increased by 15% among patients that were prescribed with two to five courses and by 37% for those with more than five courses.
The risk was calculated after adjusting for other risk factors such as obesity and smoking.
Senior study author Dr Yu-Xiao Yang said: “While our study does not show cause and effect, we think changing levels and diversity of gut bacteria could explain the link between antibiotics and diabetes risk”.
Lead study author Dr Ben Boursi added: “Gut bacteria have been suggested to influence the mechanisms behind obesity, insulin resistance and diabetes in both animal and human models.”
“Our findings are important, not only for understanding how diabetes may develop, but as a warning to reduce unnecessary antibiotic treatments that might do more harm than good,” he said.
The study found little evidence of a similar link between antibiotic use and the risk of type 1 diabetes, noted the researchers.