American and Chinese scientists have found that an antimicrobial ingredient commonly used in hand soaps and toothpastes could have adverse effects on colonic inflammation and colon cancer by altering gut microbiota, the microbes found in people’s intestines.
A study published in the journal Science Translational Medicine revealed that short-time treatment with low-dose triclosan led to low-grade colonic inflammation, and exaggerated disease development of colitis and colitis-associated colon cancer in mice.
“These results, for the first time, suggest that triclosan could have adverse effects on gut health,” said Zhang Guodong, assistant professor of food science at the University of Massachusetts Amherst, the paper’s senior author.
Zhang told Xinhua, “The toothpaste we use can enter into the intestinal tract, then impacting the gut microbiota.”
Triclosan is among the most widely used antimicrobial ingredients and is found in more than 2,000 consumer products and a National Health and Nutrition Examination survey showed that triclosan was detected in about 75 per cent of the urine samples of individuals tested in the U.S. and it is among the top ten pollutants found in U.S. rivers.
“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 Yang Caixia, a postdoctoral fellow in Zhang’s laboratory and the paper’s first author.
Zhang’s team and Chinese researchers including those from Xi’an Jiaotong University investigated the effects of triclosan on colonic inflammation and colon cancer using several mouse models.
They reported that in all mouse models tested, triclosan promoted colonic inflammation and colon tumorigenesis.
The research team found that gut microbiota was critical for the observed adverse effects of triclosan, since feeding triclosan to mice reduced the diversity and changed the composition of the gut microbiome.
However, triclosan had no effect in a germ-free mouse model where there is no gut microbiome present, nor in a genetically engineered mouse model where there is no Toll-like receptor 4 (TLR4), an important mediator for host-microbiota communications.
“This is strong evidence that gut microbiota is required for the biological effects of triclosan,” Zhang said.
This study observed that triclosan altered mouse gut microbiota, increased inflammation, increased the severity of colitis symptoms and spurred colitis-associated colon cancer cell growth.