Exposure to an ingredient known as triclosan is hard to avoid in the United States. In fact, it was found in 75 percent of urine samples from a nationally representative sample of over 2,500 participants.

While the Food and Drug Administration (FDA) banned the use of the chemical in certain products, a new study of mice led by the University of Massachusetts Amherst suggested that further scrutiny may be required. 

The study titled "A common antimicrobial additive increases colonic inflammation and colitis-associated colon tumorigenesis in mice" was published in Science Translational Medicine on May 30.

So, what do we know about this ingredient?

Triclosan is a high-volume chemical used as an antimicrobial chemical in thousands of everyday products. The FDA issued a rule in 2016 to end the marketing of wash products that contain triclosan and triclocarban. But the ingredient is still found in other products like furniture, toys, kitchenware, etc.

While there was no evidence of benefits from antibacterial soaps and washes, the chemical is still allowed in toothpaste. In a 2017 statement to Time Magazine, Colgate stated that triclosan, in safe amounts, can help in fighting harmful plaque germs that can cause gingivitis.

What were the results of the new research paper?

The study suggested, for the first time, that triclosan could have adverse effects on gut health. Led by senior author Guodong Zhang, researchers studied the effects of the ingredient on mice. In all mouse models tested, triclosan promoted colonic inflammation and colon tumorigenesis, Zhang stated.

The study used genetically engineered mice who were predisposed to inflammatory bowel disease (IBD). Since the disease was worsened upon exposure, the researchers suggested that IBD patients may need to reduce exposure to the ingredient.

Gut flora (the microorganisms living in our digestive tracts) was essential for the adverse effects to take place. When triclosan was fed to the mice, their gut flora experienced changes in diversity and composition. This was similar to what was observed in a previous human study. However, mice without gut microbiome did not experience such biological effects. 

Why do the findings of the study raise concerns?

By affecting gut microbiome, triclosan could potentially have adverse effects on colonic inflammation and colon cancer. Research has shown how certain changes to the microbiome can directly contribute to tumorigenesis. 

While we do not ingest the ingredient directly, it can seep in through the gums and into the bloodstream while brushing. Triclosan can also accumulate on toothbrush bristles, following someone who may have switched to triclosan-free toothpaste but did not change their toothbrush.

The study was limited due to the use of a mouse model and the ingestion of the ingredient, suggesting that human beings have relatively less exposure to triclosan. But further research is warranted, said the researchers.

"Because this compound is so widely used, our study suggests that there is an urgent need to further evaluate the impact of triclosan exposure on gut health in preparation for the potential establishment of further regulatory policies," said co-first author Haixia Yang, a postdoctoral fellow in Zhang laboratory.