Does Tongue Scraping Cause Cancer?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Tongue cleaning can reduce the stinky gaseous compounds that cause bad breath by up to 75 percent, whereas just brushing your teeth alone may only reduce it by 25 percent. This is why tongue cleaning has the greatest priority in the treatment of bad breath. Are there any downsides?

Well, most people do not enjoy placing an object toward the back of their throats, as it can trigger the gag reflex. Tips to help prevent this include momentarily stopping breathing during tongue cleaning. You can experiment, and if the mint flavor in toothpaste sensitizes your throat to an elevated gag reflex, you may want to clean the tongue before tooth brushing. Some recommendations even suggest doing it on an empty stomach in case vomiting ensues. That doesn’t sound very pleasant, but when tongue cleaning is practiced on a daily basis, the process evidently becomes easier and less objectionable over time.

So, the main complaint of the subjects is the gagging reflex, and also, you know, tongue carcinogenesis related to mechanical stimulation. Wait! Tongue carcinogenesis means the development of tongue cancer. “These are unpleasant side effects associated with tongue-cleaning devices.” Cancer is more than an unpleasant side effect!

I know there are alcohol-containing mouthwashes, and one might expect that to predispose people to oral cancer. I talked about this in my alcohol and breast cancer video Breast Cancer and Alcohol: How Much Is Safe?  A single sip of an alcoholic beverage—one teaspoon swished and even spit out after just five seconds—results in carcinogenic concentrations of the toxic alcohol breakdown product acetaldehyde. This is produced from ethanol in the oral cavity instantly after a small sip of a strong alcoholic beverage, and this exposure continues for at least 10 minutes after just those five seconds. And yes, this concern extends to alcohol-containing mouthwash. Researchers determined that alcohol-containing mouthwashes offer a rather low margin of safety, and that prudent public health policy should recommend generally refraining from using them. Okay, yeah, we know alcohol causes cancer, but why tongue scraping?

Well, animal experiments have shown that mechanical injuries of the tongue may be carcinogenic. Okay, even if you could extrapolate to people, are you actually injuring the tongue when you scrape it? What exactly did these experiments entail? Concerns have been raised based on an experiment in rodents showing the experimental induction of tongue cancer using carcinogenic dimethylbenzanthracene, a powerful carcinogen found in cigarette smoke and broiled meats. They evidently produced more cancer with the carcinogen if they injured the tongue using a root canal instrument. Here’s the study they cite. Indeed, scratching their tongues with essentially a little piece of barbed wire did result in more cancer, presumably because the ulceration or injury allowed for greater retention and penetration of the carcinogen into deeper tissue layers. But people don’t scrape their tongues with barbed wire. Ah, but evidently even a regular toothbrush can do it.

This appears to be the study they cite for that. But it doesn’t say a regular toothbrush, but rather “extreme mechanical stimulation.” Though then in a figure in the paper, they say just “[o]ne stroke of a dental broach was given on the tongue surface with a very light force that did not cause bleeding,” which was apparently enough to cause the cancer to show up about a month earlier. So, was it a toothbrush, extreme stimulation, or just a light scratch? Here’s the original data (and thanks to our wonderful Japanese volunteers), I am told it was no toothbrush. And even if it was, and could be extrapolated, that was with a carcinogen. So, unless you were smoking, using chewing tobacco, or eating barbequed chicken every day, there doesn’t seem to be any parallel. If you just scratch a hamster’s tongue with a barbed wire every day, no tumors develop.

And another thing…most human tongue cancers are found on the side of the tongue, and so the relationship between tongue scraping and cancer has not yet been confirmed in humans, though there is still a possibility that mechanical stimulation may be a cause. So, I’d recommend taking it easy.

In this study, they had been brushing their tongue with an electric toothbrush with medium hardness bristles, and ended up causing an increase in the expression of c-fos in tongue muscle cells, which is a protein that may be involved in cancer development.

Any kind of electrical device for tongue cleaning is not recommended, but even a manual toothbrush can cause some damage, so-called micro-bleeding. Therefore, tongue cleaning should be carried out gently, with low force, to avoid unnecessary tissue trauma. Just the top surface of the tongue should be cleaned, not the sides.

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Motion graphics by Avo Media

• alcohol
• animal studies
• bad breath
• cancer
• carcinogens
• dental health
• halitosis
• tongue scraping
• toothpaste