A common antibacterial ingredient used in liquid hand soaps, toothpaste and body washes could harm the guts leading to bowel cancer, a new study warned.
Triclosan, a common antimicrobial, found in more than 2,000 consumer products could have adverse effects on colonic inflammation and colon cancer by altering gut microbiota, the microbes found in our intestines.
Short-time exposure to low-dose triclosan caused low-grade colonic inflammation, and exaggerated disease development of colitis and colitis-associated colon cancer in mice, scientists at the University of Massachusetts Amherst found.
And because traces of the chemical has been found in three quarters of US citizens tested there was an urgent need to test its safety.
Senior author Assistant Professor Guodong Zhang "These results, for the first time, suggest that triclosan could have adverse effects on gut health.
"Triclosan (TCS) is a widely used antimicrobial ingredient and is incorporated into more than 2,000 consumer products.
"Here, our central finding is that short-time exposure to low-dose TCS caused low-grade colonic inflammation, and increased colitis and colitis-associated coloncancer in mice, which suggests a potential adverse effect of his compound on gut health."
Co-first authors Dr Haixia Yang and Weicang Wang, both from the Zhang laboratory in the food science department at UMass Amherst noted triclosan was detected in about 75 per cent of the urine samples of individuals tested in the United States and it is among the top ten pollutants found in U.S. rivers.
Postdoctoral fellow Yang 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."
The study 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, Prof Zhang reported.
Co-author, food scientist Associate Professor Hang Xiao, added: "In particular, we used a genetically engineered mouse model which develops spontaneous inflammatory bowel disease or IBD.
"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."
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.
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.
Prof Zhang said: "This is strong evidence that gut microbiota is required for the biological effects of triclosan.
"Further studies are urgently needed to better characterise the effects of TCS exposure on gut health to establish science-based policies for the regulation of this antimicrobial compound in consumer products.
"Besides TCS, many other high-volume chemicals are also used as antimicrobial ingredients in various personal care and household products.
"Compared with TCS, less is known about the health effects of other antimicrobials.
"Our research suggests the importance of evaluating the potential toxic effects of other antimicrobials on gut microbiota and associated colonic diseases to developsafe antimicrobials with minimal adverse impact on human health and the environment."
The study was published in the journal Science Translational Medicine.
In an editorial note accompanying the article, the journal said: "Antimicrobials are ubiquitous in manufactured products beyond hand soap and exist in the environment as pollutants.
"Triclosan exposure is practically unavoidable in the United States, but little is known how ingestion may affect our health.
"Although the study is limited to mouse models, this work suggests that the effects of triclosan on human health should be examined more closely."