Common toothpaste ingredient could be wreaking havoc on your gut

Triclosan is everywhere, but its days seem to be numbered.

Even if you’ve never heard of it, you’ve almost certainly come across triclosan. A highly effective antibacterial and antifungal ingredient, triclosan is found in all kinds of toothpastes, hand sanitizers, deodorants, mouthwashes, detergents, cleaning supplies—if you use household products, you’re interacting with triclosan every day. So it’s worrying that a new study, published in Science Translation Medicine on Wednesday, suggests that triclosan exposure could increase rates of colitis and colon cancer.

In the new study, led by a group of food scientists at the University of Massachusetts, Amherst, the research team fed different groups of laboratory mice—some healthy, some engineered or induced with some disease of some sort—water spiked with triclosan for three weeks, to emulate the levels found in people who had used triclosan-containing toothpaste for two weeks. All of those mice experienced exacerbated gut problems of some sort. Inflammation in the colon sprung up, leading to symptoms like rectal bleeding, diarrhea, abdominal pain, and even reduced lifespan.

It all comes down to what happens to your gut microbiome. It seems that triclosan devastated the diversity of bacteria found in the gut microbiome of those mice, and in particular killed off populations of Bifidobacterium, a “good” bacteria. The chemical transformed the intestinal flora into something antagonistic to the intestinal tissue, eliciting an inflammatory response from the body, as well as encouraging more aggressive tumor development in mice who were already battling colon cancer. This was only underscored by the fact that mice bred without gut bacteria did not experience inflammation even after exposure to triclosan.

Still, while distortions in the gut microbiome led to inflammation, it wasn’t the only key factor. The researchers also noticed that other groups of mice lacking protein called Toll-like receptor 4, important in the inflammatory response of the body, were also immune to the deleterious effects of triclosan. Without the inflammation, triclosan exposure didn’t do much to displease the gut.

Triclosan is used in thousands of different consumer products. Although the FDA banned triclosan in hand soaps and body washes in 2016, citing safety concerns and skepticism that triclosan worked any better than regular soap and water, it’s still very widely used in other products. Naturally, it finds its way into the human body—especially through everyday toothpaste use—with the research team pointing out that a National Health and Nutrition Examination Survey found traces of TCA in 75 percent of urine samples in American individuals. It’s among the top 10 biggest pollutants of U.S rivers.

When it comes to triclosan’s effects on human health, “we know very little for certain,” says Paul Terry, an epidemiologist at the University of Tennessee who was not involved with the study. “It appears to prevent gingivitis when present in toothpaste, although there are other ways to prevent gingivitis. Triclosan exposure may have health consequences, but these are not clear.” And while it’s billed as an antibacterial that’s supposed to keep products safe from germs, triclosan is “certainly not a necessary ingredient in any consumer product.” Its use is already being phased out in many cases.

Terry thinks the findings make sense, and raise serious concerns, but he’s keen on seeing confirmation, especially as it pertains to human health. A study on rodents is hardly enough to proclaim continued triclosan exposure will destroy our guts.

Patrick McNamara, an environmental engineer at Marquette University who wasn’t involved in the study, finds triclosan worrisome not just as a direct hazard to human health, but also as a contributor to antibiotic resistance in many pathogens. “There's certainly more concern about triclosan than there is benefit,” he says. “It has no added benefit in soap for washing hands. I personally avoid products that contain it, especially for my young children. The red flags around it are numerous and the benefits limited. Several hospitals have eliminated using it.”

At this point, there seem to be very few defenders of continued triclosan use in products, while the backlash is only mounting higher and higher.

A common

antimicrobial

additive increases

colonic

inflammation and

colitis-associated

colon

tumorigenesis in

mice

1. Haixia Yang¹,²,*,
2. Weicang Wang¹,*,
3. Kymberleigh A. Romano³,
4. Min Gu¹,
5. Katherine Z. Sanidad¹,⁴,
6. Daeyoung Kim⁵,
7. Jun Yang⁶,
8. Birgitta Schmidt⁷,
9. Dipak Panigrahy⁸,
10. Ruisong Pei⁹,
11. Derek A. Martin⁹,
12. E. Ilker Ozay⁴,¹⁰,
13. Yuxin Wang¹,¹¹,
14. Mingyue Song¹,
15. Bradley W. Bolling⁹,
16. Hang Xiao¹,⁴,
17. Lisa M. Minter⁴,¹⁰,
18. Guang-Yu Yang¹²,
19. Zhenhua Liu⁴,¹³,
20. Federico E. Rey³,† and
21. Guodong Zhang¹,⁴,†

1. ¹Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA.
2. ²Department of Nutrition and Food Safety, College of Public Health, Xi’an Jiaotong University, Xi’an, Shaanxi 710061, China.
3. ³Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
4. ⁴Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA.
5. ⁵Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003, USA.
6. ⁶Department of Entomology and Nematology, University of California, Davis, Davis, CA 95616, USA.
7. ⁷Department of Pathology, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA.
8. ⁸Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
9. ⁹Department of Food Science, University of Wisconsin-Madison, Madison, WI 53706, USA.
10. ¹⁰Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01003, USA.
11. ¹¹College of Life Sciences, Northwest University, Xi’an, Shaanxi 710069, China.
12. ¹²Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
13. ¹³Department of Nutrition, University of Massachusetts, Amherst, MA 01003, USA.

1. ↵†Corresponding author. Email: guodongzhang@umass.edu (G.Z.); ferey@wisc.edu (F.E.R.)

• ↵* These authors contributed equally to this work.

Triclosan triggers inflammation

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. Yang and colleagues used mouse models of colitis and colon cancer to see how brief exposures of triclosan could affect inflammation. They observed that triclosan altered mouse gut microbiota and increased inflammation in a TLR4-dependent manner. Triclosan increased the severity of colitis symptoms and spurred colitis-associated colon cancer cell growth. Although the study is limited to mouse models, this work suggests that the effects of triclosan on human health should be examined more closely.

Abstract

Triclosan (TCS) is a high-volume chemical used as an antimicrobial ingredient in more than 2000 consumer products, such as toothpaste, cosmetics, kitchenware, and toys. We report that brief exposure to TCS, at relatively low doses, causes low-grade colonic inflammation, increases colitis, and exacerbates colitis-associated colon cancer in mice. Exposure to TCS alters gut microbiota in mice, and its proinflammatory effect is attenuated in germ-free mice. In addition, TCS treatment increases activation of Toll-like receptor 4 (TLR4) signaling in vivo and fails to promote colitis in Tlr4^−/− mice. Together, our results demonstrate that this widely used antimicrobial ingredient could have adverse effects on colonic inflammation and associated colon tumorigenesis through modulation of the gut microbiota and TLR4 signaling. Together, these results highlight the need to reassess the effects of TCS on human health and potentially update policies regulating the use of this widely used antimicrobial.