The gut might be the reigning king of microbes in the body, but second in line to the throne is the oral microbiome. Together, the two form the largest microbial ecosystems in the human body¹ that work interdependently to form the oral-gut axis.

“The mouth and the gut are both important parts of the digestive system, and they are closely connected through the food we eat and the bacteria present in both areas,” says Michael Wei, DDS, a New York City-based cosmetic dentist. Your mouth is the first step of digestion, where food is chewed and then passed down to the esophagus. The bacteria and other tiny organisms living in your mouth maintain its health and protect you from disease². And every time you swallow, “oral bacteria can transfer to the stomach,“ and then to the rest of your gut, says Erin Fraundorf, DMD, MSD, an orthodontist and founder of BOCA Orthodontic + Whitening Studio.

Aside from acting as the gatekeeper of the gut, the mouth (and its health) is drastically important for promoting overall well-being. In fact, optimal oral health is even linked to boosting longevity. “Oral health, specifically your oral microbiome, sets the stage for everything in your body,” says Dr. Fraundorf. “The better your oral health, the better your gut health, and the better your overall health [will be].”

So, how can you support your oral-gut axis on a regular basis? Ahead, we caught up with two oral health experts and a gastroenterologist to get the lowdown. Spoiler alert: Brushing your teeth is only scratching the surface; you also want to be mindful of what you eat.

How poor oral health can impact the gut

Studies show poor oral health can have a profound impact on the gut. “Research has shown that the bacteria in the mouth can affect the bacteria in the gut³ and vice versa,” Dr. Wei says. He notes that poor oral health, such as gum disease, can lead to an overgrowth of harmful bacteria in the mouth that, when swallowed, can affect the gut microbiome.

It’s not inherently a bad thing to have bacteria in your mouth or gut, but the increased presence of bacteria—as well as specific harmful strains—can cause imbalances throughout the body. “Disruption in the balance of gut bacteria—dysbiosis—has been linked to various health conditions such as inflammatory bowel disease (IBD)⁴,” Dr. Wei says. And interestingly, lots of studies have found associations between IBD and mouth issues like gingivitis and periodontal disease⁵—to the point where experts theorize that the one affects the other’s progression through a unique inflammatory relationship between the gums and the gut.

Will Bulsiewicz, MD, a gastroenterologist, bestselling author of The Fiber Fueled Cookbook, and U.S. medical director of Zoe, adds that in recent years, research has shown an even stronger correlation between the gut and oral health with regards to colon cancer. “50 percent of colon cancers have a bacteria called Fusobacterium⁶. This bacterium is not native to the intestines; it’s found in the mouth,” Dr. Bulsiewicz says. Although, more research is needed to further investigate the link between the two.

That said, the link between oral and gut health isn’t all bad news. “While some of the bacteria in your mouth is harmful, some of the bacteria in your mouth is beneficial and performs protective functions. If your oral microbiome is diverse, healthy and thriving, the rest of your body will thrive, too,” Dr. Fraundorf says. The key is to support oral (and gut) health with a few key steps outlined below.

4 ways to practice good oral hygiene for optimal oral (and gut) health

1. Brush and floss your teeth regularly

Maintaining good oral health is contingent on practicing good oral hygiene, which should be brushing and flossing at least twice daily. However, if you want a more in-depth oral hygiene routine, Dr. Fraundorf’s checklist goes as follows:

• Brush at least twice a day for at least two minutes each time: Bonus points if you brush three to four times a day—but never immediately after eating, when enamel is most vulnerable to the acidic oral environment formed when eating food.
• Use an electric toothbrush: Dr. Fraundorf recommends the Oral-B iO 9 or 10 series fitted with a soft bristle brush that’s replaced at least every three months (or more frequently if you’re sick).
• Use toothpaste with fluoride or nano-hydroxyapatite (n-HA): For folks with tooth sensitivities, Dr. Fraundorf recommends using a toothpaste that also has potassium nitrate in its ingredient list.
• Floss manually and with a water flosser: Dr. Fraundorf’s go-to is Oral-B’s water flosser, which she recommends using at least once daily.
• Use a tongue scraper: Using a tongue scraper at least once daily helps remove excess bacteria and debris from the tongue’s surface.
• Use a gentle mouth rinse: Look for a mouth rinse that doesn’t contain alcohol (to avoid drying the mouth), and use it least once daily.

2. Eat oral-microbiome-friendly foods

“While it’s imperative that you brush and floss, at minimum, twice daily to maintain good oral hygiene, your diet is the biggest player and your ultimate tool for defense,” says Dr. Fraundorf. “Developing a diverse and healthy oral microbiome starts with intentionally choosing what you put in your mouth.” Her list of foods good for your teeth and oral health includes the following:

• Whole foods, vegetables, and fermented-and probiotic-rich foods
• Local, seasonal produce
• Minimally-processed foods without preservatives or artificial additives
• Limited simple carbohydrates and sugars

3. Consider mouth taping

Although mouth taping at night—aka placing a piece of tape over your mouth to avoid mouth breathing while you sleep—might not be appropriate for everyone, some doctors agree it may have some benefits for oral and gut health. For example, Dr. Bulsiewicz points out that mouth taping can create a more hospitable environment for the microbiome (both oral and gut) that continues to evolve even while you sleep.

“If patients are mouth breathers, mouth taping may help with their oral, and thus, gut health, as mouth breathing creates a dry environment which breeds bad bacteria and acid, eroding the protective barrier of the teeth and accelerating tooth decay and gum disease,” Dr. Fraundorf agrees. But consult a medical professional before trying it out to ensure it’s safe (people who have sleep apnea or other breathing conditions, for example, should not try mouth taping).

4. Don’t skip out on your dental check-ups

Finally, it’s important to visit your dentist regularly. “It’s important to maintain a comprehensive oral hygiene routine that includes brushing, flossing, and regular dental check-ups,” Dr. Wei says. This helps ensure you stay on top of any oral health concerns that can, in turn, impact the gut microbiome.

—reviewed by Jennifer Gilbert, MD, MPH