Your oral microbiome plays an important role in maintaining healthy teeth, gums and overall wellbeing. Here’s how your diet can help support it.
Most people know that sugary foods can contribute to tooth decay by feeding harmful bacteria in the mouth. But maintaining a healthy oral microbiome is not only about avoiding certain foods—it is also about eating the right ones.
Scientists are increasingly uncovering the importance of the oral microbiome, the diverse community of microorganisms living in the mouth.
It contains around 700 species of bacteria, alongside viruses, fungi and other microorganisms, and can have a significant impact on both oral and overall health.
Like the gut microbiome, the oral microbiome responds to what we eat. A balanced diet can help beneficial microbes thrive while making it harder for harmful bacteria to take over.
A thriving mouth
The mouth is home to a complex ecosystem in which different microbes occupy different environments. Some live on the surface of the teeth, while others inhabit the tongue or the spaces between the teeth and gums.
Some bacteria, however, can cause serious problems.
Streptococcus mutans, for example, thrives on sugar. It converts sugars into acids that gradually erode tooth enamel, potentially resulting in cavities.
Other bacteria can be beneficial. Species belonging to groups such as Veillonella, Actinomyces, Streptococcus and Neisseria can help prevent harmful microbes from establishing themselves in the mouth.
Maintaining a healthy balance is important not only for teeth and gums but potentially for wider health. Poor oral hygiene can allow pockets to develop between the teeth and gums, creating an oxygen-poor environment where harmful bacteria such as Porphyromonas gingivalis can flourish.
P. gingivalis is associated with gum disease and has also been linked to a range of health conditions, including cardiovascular disease, diabetes, rheumatoid arthritis and inflammatory bowel disease.
Researchers are also investigating possible links between the oral microbiome and conditions such as Alzheimer's disease, depression and certain cancers.
Recent research has found associations between particular bacteria in the mouth and an increased risk of pancreatic cancer. Other studies suggest that lower microbial diversity in the mouth may be associated with depression.
The evidence is still developing, and these associations do not necessarily mean that oral bacteria directly cause these conditions. However, they highlight the growing interest in the oral microbiome and its potential role in human health.
What to eat—and what to limit
Foods and drinks containing large amounts of added sugar are best limited because they provide fuel for cavity-causing bacteria.
It is also worth cutting back on highly processed carbohydrates, which can be quickly broken down into sugars in the mouth. Examples include white bread, crackers, biscuits, cakes and pretzels.
On the other hand, eating foods that support beneficial bacteria can help maintain a healthier microbial balance.
Beneficial microbes can compete with harmful bacteria for food and space. Some can also produce substances that inhibit or attack unwanted microbes.
"Within the broader family of these sugar loving microbes, Streptococcus, there are some [bacteria] that don't produce much acid at all, and they'll actually attack some of the microbes that do produce acid," says Laura Weyrich, an associate professor of anthropology and bioethics at Pennsylvania State University who studies the oral microbiome.
She describes these helpful bacteria as "freedom fighters" because some produce natural antimicrobial substances that can suppress harmful microbes.
For example, Streptococcus salivarius produces proteins capable of killing a range of unwanted microorganisms, including some pathogens that are resistant to conventional antibiotics.
Load up on leafy greens
One of the simplest ways to support a healthy oral microbiome may be to eat more vegetables, particularly leafy greens.
Foods such as kale, spinach, beetroot and radishes are rich in nitrate. Certain oral bacteria, including Neisseria, can convert nitrate into nitrite, which is subsequently involved in the production of nitric oxide in the body.
Nitric oxide helps regulate blood vessels and blood pressure. Research into nitrate-rich foods, including beetroot, has found potential cardiovascular benefits.
Garlic may also have benefits for oral health. Although chewing raw garlic can certainly affect your breath, it contains allicin, a compound with antimicrobial properties that can act against bacteria associated with cavities and gum disease.
A largely plant-based diet may offer additional benefits because plants contain polyphenols, a broad group of compounds with antioxidant and other biological properties.
These compounds may influence the composition and activity of microbes in the mouth, potentially helping to create an environment where beneficial bacteria can thrive.
Ultimately, protecting the oral microbiome is not about finding a single "superfood". A varied diet rich in vegetables and other minimally processed plant foods, combined with good oral hygiene and regular dental care, is a more reliable way to support a healthy mouth.
However, polyphenols can protect against harmful bacteria too. For instance, Wu's research and that of others has shown that the polyphenols found in tea can suppress the "bad" oral bacteria that cause cavities and gum disease and stop them from clumping together and attaching to the surface of teeth.
"The polyphenols inhibit one of the enzymes that is responsible for the stickiness of the plaque," says Christine Wu, professor of paediatric dentistry at the University of Illinois Chicago College of Dentistry in the US, whose research focuses on foods that could help combat oral pathogens.
In Wu's study, drinking tea also appeared to inhibit the bacteria responsible for bad breath, which live at the back of the tongue.
Other foods rich in polyphenols include many fruits, particularly dark-coloured berries. This is why, contrary to what you may expect, these sugar and acid-rich foods can benefit oral health. Wu's research has shown that drinking cranberry juice can prevent the growth of dental plaque, and inhibit the bacteria associated with cavities and periodontal disease. Honey is also packed with polyphenols and has likewise been shown to prevent plaque formation and fight against the bacteria that causes cavities.
Chewing on cheese is also thought to have some benefits for our oral communities.
In one small study by researchers in Italy, nine participants were asked to eat Grana Padano cheese each day for five days.
At the end of the study, the scientists found that the genetic signatures of the bacterial communities in their mouths had shifted slightly, with fewer of the sugar-loving S. mutans and more S. sanguinis, a bacteria more likely to be found in healthy mouths.
Cheese can also counteract some of the harm caused by S. mutans.
"Cheese is awesome because it has all the good properties of milk, but it is solid, so when you chew it the saliva increases," says Wu. "The saliva will get rid of some of the extra sugar on the tooth or in the mouth, and because saliva is neutral it buffers the acid that's produced in the mouth."
Fermented foods can also benefit your oral microbiome as they contain beneficial bacteria that compete with the "baddies."
For instance a recent review found that drinking kefir – a fermented milk product – could inhibit certain oral pathogens and stop them from producing their sticky biofilm.
However, according to Gaetano Isola, associate professor of periodontology at the University of Catania, Italy, there is no single "superfood" for oral health, and what matters much more is the overall dietary pattern.
