It’s Now Possible to Track Your Oral Microbiome

We put the new Bristle Health mouth microbiome test through the paces, and here’s what we found.

OK, OK, I confess: I only brush my teeth once a day, in the evening. Despite that, I’ve gone virtually my entire adult life without so much as a single cavity. What’s my secret? Could it be related to my oral microbiome, that underexplored sea of microorganisms living within us and that science is increasingly associating with so much of human health? To find out, I’ve been studying my mouth microbiome with a new test from Y Combinator startup Bristle.

First off, don’t get me wrong. I take care of my teeth. My bedtime ritual is sacred: I never miss a brushing. I use a good quality electric toothbrush for a full two minutes (and yes, I change the heads regularly). And I floss: every single night, even when traveling. I visit the dentist every six months where a hygienist picks me apart and tells me how everything’s fine. “You must brush a lot,” she says, and I just smile.

But we all have friends who still get cavities even though they brush all the time. Those people are the reason your office restroom smells like Colgate after lunch. They buy custom-fitted “whole mouth toothbrushes” to guarantee they catch every spot. They order hard-to-find dentist-grade toothpaste, rinse multiple times per day with anti-gingivitis mouthwash, and yet they still end up with enough cavities to keep their dentist in a Tesla Model X SUV.

Ironically for something so troublesome to so many people, the cause of most dental cavities is well understood: microscopic bacteria that generate acid that eats away at tooth enamel. Brushing is supposed to clean out those bacteria—and the particles they live on—before they cause problems. The more you brush, the more you’ll clear them out, right?

Well, sort of. Unfortunately, the 700+ microbial species in your mouth are members of a complex oral ecosystem that science is just beginning to understand. Sweeping them away entirely isn’t necessarily the goal. We don’t even know what most of the microbes do.

It’s not just cavities. Your taste receptors, especially those that detect bitter flavors, seem tuned for specific bacterial compounds, though nobody yet knows why. Spanish scientists have shown that your oral microbes help determine how you perceive the taste of wine, perhaps explaining why some people insist they actually like the taste of bad rosé. 

Cardiologists have long noticed that most of their patients have bad teeth. Periodontitis raises blood sugar and may be a cause of diabetes for some people. And don’t assume that swollen gums are no big deal. Some scientists speculate that, untreated, what seems like a minor mouth infection could over time overwhelm the body’s immune system and create an opening for a more serious chronic condition. In all more than 50 diseases, from Alzheimer’s to schizophrenia, have been linked to poor oral health.

Like most microbes, the community matters as much as an individual species.

Some microbes that appear to be “bad”—Viridans streptococci bacteria, for example, are a leading cause of heart infections—can be “good” when kept under proper control. Those same viridans are voracious eaters that outcompete their strep throat-causing cousins. They’re like lethargic bouncers at a fancy nightclub: menacing enough to prevent trouble, but not active enough to actually cause it—as long as they don’t get out of control.

Then of course there’s cavities. When the acidic secretions of sugar-loving Streptococcus mutans were first shown to harm tooth enamel, scientists tried to develop a vaccine to rid us of the pesky buggers. But it turned out that, like most microbes, the community matters as much as an individual species. We know that the oral microbiota of preschoolers who will later develop cavities are different from those who don’t, but exactly which ones make the difference, nobody is completely sure.

Testing with Bristle

If you want to learn more about your own microbiome, these days it’s easy to find consumer-priced gut tests. I’ve lost track of the dozens of companies that, for $100–$300, will mail you a poop collection kit that after a few weeks processing time will tell you in varying levels of detail the breakdown of microbes in your gut. The underlying microbiome sequencing technology is the same, and I’ve often wondered why these companies don’t offer an oral microbiome option.

Now that’s starting to change. Viome (whose gut and blood versions I’ve tried previously) just announced a $350 “full body” option that includes the mouth microbiome. Nebula Genomics includes a basic oral microbiome report with its various DNA sequencing products (priced from $99–$1,000). And Bristle, a new San Francisco-based startup partially funded by 23andMe co-founder Anne Wojcicki, now ships a test specifically focused on the oral microbiome.

Over the years, I’ve tested my mouth microbiome dozens of times, so when Bristle recently sent me a review copy (normal price is $120), I eagerly put it through the paces.

Hands down, the Bristle test is the easiest microbiome test I’ve ever tried. No yucky toilet paper, no cotton swabs. You just spit into a small vial and mail it back in a prepaid mailer. It’s not a lot of spit either: one good pucker, and you’re done. 

Three weeks later, an email announced my results. I received access to a web page with an easy-to-understand summary of my results, a lengthy “oral health guide,” and a raw breakdown of the specific microbes and abundances found in my sample.

The Bristle Health test kit

No decay for me

The summary section is the easiest to follow. My results are scored in five categories, each with a single 1–10 rating and how I compare to healthy people. On the first and second categories, “beneficial bacteria” and “tooth decay,” my results are through the roof, thus confirming my apparent resistance to cavities. 

But more worryingly, I score poorly on “gum inflammation” (9.4, where healthy people are 2.2) and “halitosis” (I’m a very high 9.2 out of 10. They don’t say if that’s healthy, and I don’t want to know). A final score for “gut inflammation” (I’m moderate 4.1) seems like it would be unrelated to teeth, but as I described, the oral microbiome affects the entire body. 

The author’s tooth decay results

What can I do about it?

My good scores related to tooth decay are reassuring, but what should I think about the other results? Here the company offered me a list of recommendations, each labeled with how confident they are with the science. Fluoride, for example, clearly helps prevent tooth decay, and Bristle recommends a couple of products that can beef up my tooth enamel. They also suggested a couple of brands of toothpaste to try, specifically some containing “nano-hydroxyapatite.” Don’t rinse after using it, though, they add; you want to give the substance time to settle on the enamel.

Bristle also lists a few other treatments, but with less confidence, such as a few commercially available mouth rinses that might help with bad breath. Other suggestions, like probiotic lozenges, are labeled “being investigated” because although the idea of treating my oral microbiome with special probiotics sounds intriguing, Bristle told me they haven’t yet concluded that the scientific evidence is quite there.

How will the science get there? Obviously Bristle hopes that you’ll help: By collecting more samples like mine (and yours), the company wants to build a massive database that can unlock some of the secrets that remain hidden due to lack of data. Meanwhile—and a refreshing contrast with other microbiome testing companies—I’m able to download the raw data for my results. CEO Danny Grannick goes further. “You own your personal data and control access to your results, so we can’t sell it to companies,” he says.

The microbiome changes a lot from test to test, even if you think you’ve done nothing special.

It’s too early to tell what insights the company may find, but unlike previous low-cost microbiome tests based on older technology, Bristle is wise to start with the latest “WGS” (whole genome sequencing) high-resolution technology from the start. Although this increases their costs, it gives them visibility into the whole family of microbes, including non-bacterial fungi and archaea. 

My one caveat, which I’ve learned from my own regular testing, is that the microbiome changes a lot from test to test, even if you think you’ve done nothing special. What you had for dinner last night, how much you slept and how much your mouth was open, even when and how you took the test—all of these variables matter, and I’m not sure how informative a single test can be. Bristle recognizes that, and strongly encourages you to buy a subscription (20 percent discount if you order 4 per year). I think they’re right, and if you have a specific problem and are serious about improving your oral hygiene, a subscription is the lowest-cost WGS microbiome test you’ll find.

Until my next test confirms a consistent pattern one way or another, I’m not going to over-interpret my results. Although my dentist says my gums are fine, and my wife doesn’t complain about my breath, I’ll try some of the interventions they suggest—especially the mouth rinse. I’ll take their reassurance that, at least for preventing tooth decay, my microbes are happy with only one brushing a day.  

Just don’t tell anybody, okay?

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