Pesticides Endanger People's Good Gut Microbes

Key Takeaways

• British researchers have identified 168 pesticides, flame retardants and other chemicals that could harm helpful bacteria in the gut

• The lab research suggests exposure to these chemicals might also encourage antibiotic resistance

• More study needs to be done to test out these findings in people

WEDNESDAY, Nov. 26, 2025 (HealthDay News) — Pesticides used on commercial farms, and even your backyard flower bed, could be harming the healthy bacteria that live in your gut, new research suggests. 

And it’s not only pesticides: British researchers found that other chemicals ubiquitous in modern homes — flame retardants and plastics compounds — may also be toxic to your “microbiome,” the trillions of helpful germs living in the digestive tract. 

“We’ve found that many chemicals designed to act only on one type of target, say insects or fungi, also affect gut bacteria,” said study lead author Indra Roux, of the University of Cambridge’s MRC Toxicology Unit. “We were surprised that some of these chemicals had such strong effects. For example, many industrial chemicals like flame retardants and plasticizers — that we are regularly in contact with — weren’t thought to affect living organisms at all, but they do.”

The findings were published today in the journal Nature Microbiology.

In their research, Roux and colleagues lab-tested 1,076 chemicals on 22 different species of helpful bacteria commonly found in the human gut. 

As they noted in a university news release, that’s just a fraction of the approximately 4,500 helpful bacterial species known to live in or on the human body.

Disruptions in the microbiome can trigger a host of health issues, including obesity, gastrointestinal issues, immune conditions and even mental health problems.

In all, the Cambridge team identified 168 chemicals that appeared to harm gut bacteria, curbing their healthy growth. 

The research also showed that attempts by bacteria to resist these chemicals led some species to become resistant to a common antibiotic, ciprofloxacin. That could make treating infections with antibiotics more difficult, the study authors said. 

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According to the authors, the only way to cut down on exposures to pesticides is to wash fruit and vegetables before consumption, and not to use pesticides in your home garden.

Many chemicals, such as pesticides, are designed to target insects, but their effect on microbiome bacteria hasn’t been investigated till now. The new data might be useful in creating safer chemicals, said study senior author Kiran Patil, also of the MRC Toxicology Unit.

“The real power of this large-scale study is that we now have the data to predict the effects of new chemicals, with the aim of moving to a future where new chemicals are safe by design,” he said in the news release. 

The researchers noted that these studies were conducted in the lab, so exact exposures to pesticides and other chemicals by bacteria in the gut remain unknown.

“Now we’ve started discovering these interactions in a laboratory setting it’s important to start collecting more real-world chemical exposure data, to see if there are similar effects in our bodies,” Patil said. 

More information

Find out more about the microbiome at the National Human Genome Research Institute.

SOURCE: University of Cambridge, news release, Nov. 26, 2025

What This Means For You

New research suggests that pesticides and other chemicals you ingest might be harming helpful bacteria essential to your gut health.