刮舌头比刷舌头更能去口臭，可舌头上的细菌也在帮你降血压

Have you ever finished brushing, stuck your tongue out at the mirror, and seen a white layer on it?

In recent years, one small tool has been especially hot on social media: the tongue scraper.

A strip of stainless steel or copper bent into a U, pulled from the root of the tongue to the tip, and that white coating comes right off — videos often caption it 'gross but satisfying.'

One market research firm estimates the global tongue-scraper market will grow past a billion dollars over the next decade.

Tongue scraping itself isn't new at all.

India's traditional medicine, Ayurveda, long ago made tongue scraping a step of every morning.

What's new is that there's now more research to answer a simple question: does it actually work?

The answer comes in two halves.

The first half is about bad breath, the second about blood pressure — and the second is more surprising.

First, bad breath.

Most bad breath comes from the back of the tongue.

Bacteria there break down proteins and produce volatile sulfur compounds — that rotten-egg smell.

In 2004, the University of São Paulo ran a crossover trial in which 10 subjects cleaned their tongues with a toothbrush and then a tongue scraper.

The toothbrush cut sulfur compounds by 45%, the scraper by 75%.

A sizable gap, but the sample was just 10 people.

In 2006, a Cochrane systematic review screened the relevant research; only 2 small trials met its standards.

Its conclusion: tongue scrapers have a short-term effect on bad breath, slightly better than toothbrushes, but the evidence is limited and there's no long-term data.

Put simply, scraping freshens your breath for a while afterwards, but it's not a once-and-for-all fix.

If the story ended here, it would just be an ordinary life hack.

The really interesting part is the second half.

The bacteria on your tongue aren't all smell-making 'bad guys.'

One group of them, such as Neisseria and Rothia, does a job few people know about.

When you eat vegetables like spinach, beetroot and lettuce, you take in a lot of nitrate.

After nitrate is absorbed, roughly a quarter returns to your mouth through saliva.

At this point, these tongue bacteria convert the nitrate into nitrite, which, once swallowed, is turned into nitric oxide inside the body.

Nitric oxide relaxes and widens blood vessels, and blood pressure drops as a result.

In other words, some of the bacteria in your mouth are a link in your body's blood-pressure-lowering system.

So what happens if you wipe these bacteria out?

In 2019, a research team had 26 healthy volunteers use a strong chlorhexidine antibacterial mouthwash twice a day for a week.

Their average systolic blood pressure rose from 113 to 115 millimeters of mercury.

Two points may not sound like much, but this was a change in healthy people over just one week, and it points the same way as earlier research: wipe out mouth bacteria on a large scale, and blood pressure goes up.

After they stopped the mouthwash, the nitrate-reducing bacteria on the tongue came back.

So does tongue scraping also accidentally harm these 'good bacteria'?

The same study gave a somewhat surprising answer.

People who normally cleaned their tongues twice a day or more had tongue microbiomes leaning toward producing nitric oxide, with relatively fewer ammonia-producing bacteria.

A reasonable explanation: scraping is physical removal — it takes off the thick coating and the many anaerobic bacteria in it, without wiping out bacteria wholesale the way chemical disinfection does; once the coating is thinner,

the environment actually suits the useful bacteria better.

The researchers wrote in their conclusion: managing the tongue microbiome through regular cleaning, together with adequate dietary nitrate, may help lower resting systolic blood pressure.

A caveat: this was a 26-person study, and it's too early to say 'tongue scraping lowers blood pressure.'

But at least we can say: tongue scraping probably doesn't harm this system; what really deserves attention is the habit of using strong antibacterial mouthwash every day.

So, putting all this together, the takeaway is actually quite practical.

To improve your breath, a scraper works better than a toothbrush, but you have to keep at it daily, and the effect is temporary.

If bad breath is severe for a long time, the problem may be gum disease or even acid reflux — then you should see a doctor; a pricier scraper won't fix it.

As for mouthwash, unless your dentist recommends it, there's no need to use the strong antibacterial kind every day.

One last question for you: if the bacteria in your mouth really are helping lower your blood pressure, would you still want to kill them all?