Thursday, 1 January 2026

Hundreds of Everyday Chemicals Found To Damage Beneficial Gut Bacteria

BY J. GARGET, U. OF CAMBRIDGE, DEC. 31, 2025


A broad chemical screen reveals that substances designed for industrial and agricultural use may have unintended effects on the microbes that support human health.
 Credit: Stock



Many everyday chemicals can damage beneficial gut bacteria and potentially fuel antibiotic resistance, prompting calls to rethink chemical safety testing.

A sweeping laboratory analysis of synthetic chemicals has uncovered 168 substances that can harm beneficial bacteria living in the human gut. These compounds interfere with the growth of microbes that play an essential role in maintaining health.

Many of the chemicals identified are commonly encountered through everyday exposure, including food, drinking water, and the surrounding environment. Until now, most were assumed to have little or no impact on bacteria.

When gut microbes adapt in response to these chemical stresses, some also develop resistance to antibiotics such as ciprofloxacin. If similar changes occur inside the human body, this could make bacterial infections more difficult to treat.

A broad screen reveals hidden toxicity

The study, led by researchers at the University of Cambridge, examined how 1076 chemical contaminants affect 22 different species of gut bacteria under laboratory conditions.


Chemicals that have a toxic effect on human gut bacteria include pesticides, like herbicides and insecticides, that are sprayed onto food crops. These chemicals stifle the growth of gut bacteria thought to be vital for health. 
Credit: Ailen Fernandez-Lande/ University of Cambridge



Among the harmful substances were pesticides, including herbicides and insecticides applied to crops, as well as industrial compounds commonly used in flame retardants and plastics.

Why gut microbes matter for health

The human gut microbiome consists of roughly 4,500 bacterial species that support many critical functions in the body. Disruptions to this complex system have been linked to digestive disorders, obesity, and changes in immune function and mental health.

Despite this importance, traditional chemical safety testing does not account for effects on gut bacteria. These assessments typically focus on intended targets, such as insects in the case of insecticides, while overlooking potential impacts on the human microbiome.


Kiran Patil, senior author of the study, says the study has provided the data to predict the effects of new chemicals, with the aim of moving to a future where new chemicals are safe by design.
 Credit: Jonathan Settle/University of Cambridge



The researchers have used their data to create a machine learning model to predict if industrial chemicals – whether already in use, or in development – will be harmful to human gut bacteria.

The research, including the new machine learning model, was published in the journal Nature Microbiology.

Rethinking chemical safety standards

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

Professor Kiran Patil in the University of Cambridge’s MRC Toxicology Unit and senior author of the study said: “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.”


Roux was surprised to find that many industrial chemicals we’re regularly in contact with affect human gut bacteria, even though they weren’t previously thought to affect living organisms at all. 
Credit: Jonathan Settle/University of Cambridge



Dr Stephan Kamrad at the University of Cambridge’s MRC Toxicology Unit, who was also involved in the study, said: “Safety assessments of new chemicals for human use must ensure they are also safe for our gut bacteria, which could be exposed to the chemicals through our food and water.”

From lab findings to real-world exposure

Very little information is available about the direct effects of environmental chemicals on our gut microbiome, and in turn our health. The researchers say it’s likely our gut bacteria are regularly being exposed to the chemicals they tested, but the exact concentrations reaching the gut are unknown. Future studies monitoring our whole-body exposure will be needed to assess the risk.

Patil said: “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.”

In the meantime, the researchers suggest the best way to try and avoid exposure to chemical pollutants is to wash our fruit and vegetables before we eat them, and not to use pesticides in the garden.


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1 comment:

  1. And yet not a mention of the preservatives used in processed food to keep them bacteria free for a long time.

    ReplyDelete

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