People who have taken certain antibiotics repeatedly may be at an increased risk of type 2 diabetes, according to a new study.
Researchers found that people in the study who had ever been prescribed two or more courses of specific types of antibiotics were more likely to be diagnosed with type 2 diabetes than people who had never been prescribed these antibiotics, or had taken just one course. The antibiotics in the study came from one of four categories: penicillins, cephalosporins, quinolones and macrolides.
The study "raises a red flag about the overuse of antibiotics, and it should make us much more concerned about this overuse," said Dr. Raphael Kellman, a New York City internist who was not involved in the study. "We should certainly be more judicious, more cautious when we use antibiotics."
Physicians should keep in mind that one of the complications of prolonged use of antibiotics may be diabetes, Kellman told Live Science.
In people with type 2 diabetes, the cells of the body stop responding to the hormone insulin, which normally causes cells to take in sugar from the blood. People with the condition tend to have levels of sugar in their blood that are too high.
In the study, the researchers looked at a database of people in the United Kingdom. The researchers examined the number of antibiotic prescriptions that were given to about 200,000 people with diabetes at least one year before the individuals were diagnosed with the condition. The scientists then compared that total with the number of antibiotics prescribed to 800,000 people who didn't have diabetes, but were the same average age as the patients. The ratio of men to women in the two groups was also the same.
The researchers found that the more courses of antibiotics people were prescribed, the greater their risk of diabetes. [7 Bizarre Drug Side Effects]
For example, the risk of type 2 diabetes in people who had been prescribed between two and five courses of penicillin increased 8 percent, compared with people who had taken one course of penicillin or none. In those who had been prescribed more than five courses of the antibiotic, the risk increased 23 percent compared with the one- or no-course group.
Among people who had been given two to five courses of quinolones, the likelihood of being diagnosed with diabetes grew by 15 percent, and it increased 37 percent among those who had received more than five courses.
However, the people in the study who had been prescribed a single course of antibiotics did not have an increased risk of developing type 2 diabetes, compared with those who had never taken antibiotics.
Exactly how the repeated use of antibiotics might be linked diabetes is not clear, but the researchers said they suspect that it be may be related to an imbalance in people's gut bacteria brought on by antibiotics.
"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," study co-author Dr. Yu-Xiao Yang, an assistant professor of medicine and epidemiology at the University of Pennsylvania, said in a statement.
An imbalance in gut bacteria has been previously linked to the mechanisms behind obesity, insulin resistance and diabetes in animal and human studies, the lead author of the study Dr. Ben Boursi, a researcher at the University of Pennsylvania, said in the statement.
Kellman agreed, saying, "I think this study further supports the idea that problems with the microbiome can lead to metabolic dysfunction, inflammation and even diabetes."
Moreover, the antibiotics that are prescribed by doctors are likely not the only problem, he added. "Most of the antibiotics that are consumed come from the food that we eat," such as poultry and other types of meat.
In general, the rise in the incidence of type 2 diabetes in recent years might have something to do with the antibiotics in food, said Kellman, who also wrote the book "The Microbiome Diet" (Da Capo Press, 2014).
"Studies like this will bring out a new awareness" of the connection between diet and chronic diseases, he said.
The new study was published today (March 24) in the European Journal of Endocrinology.