How common medications impact your gut health

The human intestine contains a dense network of microorganisms, which are known collectively as the gut microbiome. The gut microbiome is involved with digestion and helps keep dangerous bacteria from the body.

However, medications like antibiotics can negatively impact the gut microbiome, since they kill some of the body's good bacteria. Now, new research suggests that other medications can also disrupt the gut microbiome and increase the risk of gut infections.

In one study, researchers from the University of Tübingen in Germany studied 53 common non-antibiotic medications, including allergy treatments, antidepressants, and hormone drugs. They tested the effects of these drugs in both synthetic and real human gut microbial communities and found that a third of these medications promoted the growth of Salmonella, bacteria that can cause severe diarrhea.

"The scale of it was utterly unexpected. Many of these non-antibiotics inhibit useful gut bacteria, while pathogenic microbes such as Salmonella Typhimurium are impervious," said Lisa Maier, a professor at the University of Tübingen and the study's senior author. "This gives rise to an imbalance in the microbiome, which gives an advantage to the pathogens."

Overall, the researchers found that certain medications reduced the total biomass of gut microbiota and harmed the biodiversity of microbes that typically compete for nutrients with pathogens — something that ultimately led to a more favorable environment for pathogens like Salmonella to grow in the gut.

In another study, researchers from the Yale School of Medicine analyzed medical records and pharmacy claims data from 1 million patients enrolled in universal health insurance in Montreal, Canada, over a 10-year period to determine the incidence of gastrointestinal (GI) infections.

The researchers identified 21 common prescription, non-antibiotic drugs that increased people's risk of GI infections to the same degree as antibiotics. Of these drugs, around half were associated with changes in microbiome composition. Four drugs (congestive heart failure medication digoxin, the anti-seizure and anti-anxiety drug clonazepam, stomach acid reducer pantoprazole, and anti-psychotic medication quetiapine) were associated with an increased risk of GI infection after exposure to a pathogen. 

"Most microbiome studies only consider current medications, but our results show that past drug use can be just as important as it is a surprisingly strong factor in explaining individual microbiome differences," said Oliver Aasmets, the study's lead author.

Commentary

Currently, scientists say that more research is needed to understand the effects of medications on the gut microbiome, especially since there may be significant differences among people. While one person may benefit from a drug, another may experience a range of side effects.

"Our overall hypothesis is that in some of these cases, differences in people's gut microbiomes could contribute to these different responses to drugs," said Andrew Goodman, chair of microbial pathogenesis at the Yale School of Medicine and principal investigator of the Yale study.

In the future, Goodman said his team plans to study if they can use people's microbiomes to predict who could have the greatest risk of infection while taking certain medications.

"I think there's a possibility for interventions in the future where you could alter a person's microbiome so that they would no longer have these risks associated with a drug that would benefit their health," Goodman said.

Meanwhile, Maier emphasized the importance of understanding the impact of medications on the gut microbiome and people's overall health.

"While the necessity of drugs is unnegotiable, even drugs with supposedly few side-effects can, so to speak, cause the microbial firewall in the intestine to collapse," she said. "It's already known that antibiotics can damage the gut microbiota. Now we have strong signs that many other medications can also harm this natural protective barrier unseen. This can be dangerous to frail or elderly people."

"If you disrupt the microbiome, you open the door to pathogens — it is an integral component of our health and must be considered as such in medicine," Maier added.