Study finds common toothpaste ingredient may up colon cancer risk

A common antimicrobial ingredient triclosan, found in hand soaps and toothpastes, may alter gut bacteria and increase the risk of colon cancer, a study has found.

The study, published in the journal Science Translational Medicine, suggests that short-time treatment with low-dose triclosan caused 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 Guodong Zhang from the University of Massachusetts Amherst in the US.

Triclosan is among the most widely used antimicrobial ingredients and is found in more than 2,000 consumer products, researchers said.

"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 Haixia Yang, a postdoctoral fellow in Zhang laboratory.

Researchers investigated the effects of triclosan on colonic inflammation and colon cancer using several mouse models. In all mouse models tested, triclosan promoted colonic inflammation and colon tumorigenesis.

"In particular, we used a genetically engineered mouse model which develops spontaneous inflammatory bowel disease or IBD," said co-author and food scientist Hang Xiao.

"Also, treatment with triclosan significantly increased disease development of IBD in the mice, suggesting that IBD patients may need to reduce exposure to this compound," Xiao said.

In a series of experiments designed to explore mechanisms, the research team found that gut microbiota is critical for the observed adverse effects of triclosan.

Feeding triclosan to mice reduced the diversity and changed the composition of the gut microbiome, a result similar to what was observed in a human study conducted by others, Zhang said.

Also, 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.