What you eat can play an important role in maintaining a healthy oral microbiome — the community of bacteria and other microorganisms living in the mouth.

The oral microbiome contains around 700 bacterial species, along with viruses, fungi and other microorganisms. While some bacteria contribute to cavities and gum disease, others can help prevent harmful microbes from taking over.

One of the main threats is Streptococcus mutans, a bacteria that feeds on sugar and produces acids that damage tooth enamel, potentially causing cavities. Other harmful microbes, including Porphyromonas gingivalis, can thrive between the teeth and gums and are associated with gum disease and several other health conditions.

Maintaining a diverse mix of beneficial microbes is therefore important. Diet can influence which bacteria thrive in the mouth, meaning oral health is about more than brushing and flossing alone.

What to eat

Foods high in refined sugar should be limited, as they provide fuel for cavity-causing bacteria. Processed carbohydrates such as white bread, crackers, biscuits, cakes and pretzels can also be easily broken down into sugars in the mouth.

Leafy green vegetables such as kale, spinach, beetroot and radishes may support beneficial bacteria because they are rich in nitrate. Oral bacteria such as Neisseria can convert nitrate into compounds involved in processes that may benefit cardiovascular health.

Garlic may also have benefits despite its effect on breath. It contains allicin, a compound that can attack bacteria associated with cavities and gum disease.

A diet rich in plant foods can provide polyphenols, compounds that may help suppress harmful oral bacteria. Research suggests polyphenols found in tea can inhibit bacteria linked to cavities and gum disease and reduce their ability to stick to teeth. Tea may also help suppress bacteria associated with bad breath.

Dark-coloured berries and other fruits are also rich in polyphenols. Research cited in the article suggests cranberry juice may inhibit dental plaque and bacteria associated with cavities and periodontal disease.

Cheese may offer another benefit. A small study found that eating Grana Padano cheese was associated with changes in oral bacteria, including fewer S. mutans and more S. sanguinis, which is more commonly found in healthy mouths. Chewing cheese also increases saliva production, helping wash away sugars and neutralise acids.

Fermented foods such as kefir may also support oral health by providing beneficial bacteria that compete with harmful microbes.

Overall diet matters most

Researchers caution that there is no single “superfood” for maintaining a healthy oral microbiome.

Instead, regularly consuming refined sugars and easily fermentable carbohydrates can favour bacteria that produce and tolerate acids, potentially disrupting the balance of the oral microbiome.

A diet based on whole vegetables, fruits, legumes, whole grains, fibre and complex carbohydrates, while limiting frequent refined-sugar consumption, is considered more supportive of a stable oral ecosystem.

A Mediterranean-style diet, which emphasises fruits, vegetables, whole grains and healthy fats, has also been associated with less severe gum disease.

Food, however, is only part of the equation. Regular brushing and flossing remain essential for controlling harmful bacteria and maintaining oral health.

The simplest approach, researchers say, is to maintain a balanced diet rich in vegetables and leafy greens, choose whole foods over refined carbohydrates and limit sugar, particularly sugary drinks.