Taking too many antibiotics could raise the risk of Type 2 diabetes, according to new research.
A study of more than a million people, including 170,500 with the disease, found a clear link between higher numbers of prescriptions for the drugs and having a diabetes diagnosis.
Increasing amounts of antibiotics led to a greater chance of developing the disease.
Antibiotics may affect the "microbiota" of bugs in the gut, some of which are known to influence metabolism. But an alternative explanation could be that people with as-yet undiagnosed diabetes may be more prone to infection, and therefore use more antibiotics, say the scientists.
The researchers, whose findings appear in the Journal of Clinical Endocrinology & Metabolism, tracked antibiotic prescriptions made out for 170,404 Danes with Type 2 diabetes and 1.3 million people who did not have the disease.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Five or more prescriptions over a period of up to 15 years was associated with a 53 per cent increase in risk compared with being given antibiotics just once, or never.
The relative risk was slightly higher for antibiotics effective against a narrow range of bacteria as opposed to broad-spectrum drugs.
Study author Dr Kristian Mikkelsen, from Gentofte Hospital in Hellerup, Denmark, said, "In our research, we found people who have Type 2 diabetes used significantly more antibiotics up to 15 years prior to diagnosis compared to healthy controls.
"Although we cannot infer causality from this study, the findings raise the possibility that antibiotics could raise the risk of Type 2 diabetes. Another equally compelling explanation may be that people develop Type 2 diabetes over the course of years and face a greater risk of infection during that time."
Type 2 diabetes is one of the greatest health problems facing the UK and other countries in the western world.
