Everyday chemicals are quietly damaging beneficial gut bacteria
A large study has revealed that dozens of widely used chemicals can damage beneficial gut bacteria. Many of these substances, found in pesticides and everyday industrial products, were never thought to affect living organisms at all. When gut bacteria are stressed by these chemicals, some may also become resistant to antibiotics. The research raises new questions about how chemical exposure could be influencing human health behind the scenes.
Scientists have completed a large laboratory analysis of widely used human-made chemicals and found that 168 of them are harmful to bacteria that normally live in a healthy human gut. These substances slow or stop the growth of microbes that play an important role in supporting overall health.
Many of the chemicals identified are ones people are likely to encounter through everyday exposure, including food, drinking water, and the environment. Until now, most were not believed to interfere with bacteria at all.
Links to Antibiotic Resistance Raise New Concerns
When gut bacteria are exposed to these chemical pollutants, some change how they function in an attempt to survive. In certain cases, this adaptation also makes the bacteria resistant to antibiotics such as ciprofloxacin. If similar changes occur inside the human body, infections could become more difficult to treat.
The study was led by researchers at the University of Cambridge and involved testing 1076 different chemical contaminants on 22 species of gut bacteria under laboratory conditions.
Pesticides and Industrial Chemicals Among the Most Harmful
The chemicals shown to damage gut bacteria include pesticides such as herbicides and insecticides commonly applied to crops. Industrial compounds used in products like flame retardants and plastics were also found to be toxic to these microbes.
The human gut microbiome contains roughly 4,500 different types of bacteria that help keep the body functioning properly. When this delicate system is disrupted, it can contribute to a wide range of health problems, including digestive issues, obesity, weakened immune function, and effects on mental health.
Why Chemical Safety Testing Misses Gut Health
Current chemical safety evaluations typically do not account for the gut microbiome. This is because chemicals are designed to target specific organisms or processes, for example insecticides should target insects.
Using the data from their experiments, the researchers developed a machine learning model to help predict whether industrial chemicals -- whether already in use, or in development -- are likely to harm human gut bacteria. The findings and the new model were published in the journal Nature Microbiology.
Researchers Call for a New Approach to Chemical Safety
Dr. Indra Roux, a researcher at the University of Cambridge's MRC Toxicology Unit and the study's first author, 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 plasticizers -- that we are regularly in contact with -- weren't thought to affect living organisms at all, but they do."