Study coauthor Tove Fall, PhD, a professor of molecular epidemiology at Uppsala University in Sweden, says it’s well-known that antibiotics can cause short-term changes to the gut microbiome. The latest findings suggest these changes could be longer-lasting than previously thought.

Here’s what the research found, plus what foods doctors recommend to support your gut when taking antibiotics.

For the study, researchers analyzed drug register data and compared it with detailed gut microbiome mappings of nearly 15,000 adults in Sweden. The gut microbiome data compared people who received different types of antibiotics and those who did not receive antibiotics during the eight-year study period.

The study specifically looked at 11 types of antibiotics, including drugs commonly prescribed in the United States like penicillin V, tetracyclines, and clindamycin — as well as less common medicines like fluoroquinolones, used only for the most severe infections, and flucloxacillin, which is not approved in the United States.

The researchers discovered that the impact on the gut microbiome differed based on the type of antibiotic.

The biggest changes involved clindamycin, fluoroquinolones, and flucloxacillin. Participants who took any of these drugs saw a 10 to 15 percent drop in the microbial diversity of their gut — which for some people lasted even when they’d taken antibiotics four to eight years earlier.

On the other hand, penicillin V was linked to small and short-lived microbiome changes.

The long-term effects of these gut microbiome changes are still being explored, Dr. Fall says.

“One well-known implication is the risk of rare infections in the gut, for example with Clostridium difficile, that can cause severe diarrhea,” she says. “There might also be an impact on cardiometabolic [heart disease] risk and other diseases, but that needs to be clarified further.”

The gut microbiome contains a range of bacteria, points out Peter Stein, MD, a gastroenterologist and director of endoscopy at Northwell Health in Westchester County, New York. “Our gut microbiome is incredibly complex and robust, with thousands of different types of bacteria normally inhabiting our healthy intestines,” he says. “These bacteria are beneficial to our health, acting to aid in digestion, produce essential nutrients, and ward off dangerous bacteria that would not normally reside in our gut.”