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Healthy Mouth, Healthy Body

Healthy Mouth, Healthy Body

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Why we shouldn’t ignore the oral microbiome

If you’re like me, you’d prefer not to dwell on the millions of bacteria living in your mouth. But if you care about your health, you can’t ignore the oral microbiome!

Up to 700 different species of bacteria live in various niches within the mouth.[1],[2],[3] Even individuals with good oral hygiene have up to 100,000 bacteria on each tooth, and the numbers can rise to a billion per tooth in less well-maintained mouths (yikes!)[4]

Some oral bacteria are benign or even beneficial (such as those that play a critical role in nitric oxide production),[5] while others are responsible for tooth decay or periodontitis (infections of the gums and tooth-supporting structures).[6],[7],[8] A dynamic balance of neighboring bacteria is crucial in determining whether harmful bacteria proliferate or not.[9],[10] If we’re not careful, this balance can shift from a healthy, symbiotic relationship to disease.

Evidence began to emerge in the 1980’s of possible linkages between periodontal disease and systemic diseases.

In chronic periodontitis, for example, the healthy microbiota on the tooth surface is replaced by a consortium of bacteria that gradually destroy periodontal tissue. However, research continues to show that this not only impacts the health of the oral cavity. Evidence began to emerge in the 1980’s of possible linkages between periodontal disease and systemic diseases.[11] We now know that diabetes is a risk factor for periodontal disease, but, at the same time, periodontal disease exacerbates type 2 diabetes.[12],[13],[14] Researchers at Tufts University, who are studying this phenomenon, note the importance of developing personalized strategies for maintaining a healthy oral microbiota in order to manage these risks.[15].

Let’s examine the impact of the oral microbiome on both oral and systemic disease, and how diet and nutrition may help.

The oral microbiome in health and disease

Dental cavities. Dental cavities are driven primarily by Streptococcus mutans (S. mutans), a member of the “viridans group” streptococci, which together comprise up to 80% of early dental plaque.[16],[17] S. mutans metabolizes sucrose to lactic acid and other organic acids, which degrade the tooth’s enamel.[18] Repeated acid attacks can break down the hard enamel on the surface of teeth, leading to tooth decay. The bacteria in plaque also trigger an inflammatory response, resulting in the breakdown of the gums, bone, and other supporting structures of the teeth.[6],[19],[20]

Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.

Along with many other factors, an overabundance of oral Streptococcus also increases the risk of stroke and heart attack.[21] The culprit is a specific serotype of S. mutans, which produces a collagen-binding protein known as Cnm that interferes with blood clotting, thereby increasing the risk of hemorrhagic stroke (the type of stroke in which in which blood vessels in the brain rupture, causing bleeding).[22],[23],[24] Individuals with Cnm-positive S. mutans had a 14-fold higher risk of cerebral microbleeds compared with individuals who tested negative.[25]

Another oral Streptococcus species, S. mitis, has an opposite but equally damaging effect: it promotes blood clotting, and may increase for blockage of the arteries leading to ischemic heart attack or stroke.[26],[27] Scientists who isolated blood clots from patients with stroke found unmistakable evidence of S. mitis infection in 84% of the aspired clots.[26] They concluded that “Streptococcal bacteria, mostly of oral origin, may contribute to the progression and thrombotic events of cerebrovascular diseases.”

Periodontitis. In addition to type 2 diabetes, periodontitis – which affects nearly half of adults over the age of 30 –[28] also has been implicated as a possible risk factor for heart disease,[29],[30],[31] stroke,[22] rheumatoid arthritis,[32],[33] inflammatory bowel disease,[34] Alzheimer’s disease,[35] and cancer (including oral, esophageal, colorectal, lung, breast, and pancreatic malignancies).[36],[37],[38],[39],[40]

The data suggest that oral pathogens associated with periodontitis can enter the bloodstream and accumulate in internal organs, where they interact with other factors to increase disease susceptibility.[41],[42],[43] A pathogen that triggers the development of periodontitis, Porphyromonas gingivalis,[44] has been found in the arterial plaque of heart disease patients, and may contribute to the initiation or acceleration of atherosclerosis.[45],[46] P. gingivalis also increases the risk of pancreatic cancer, among the most aggressive cancers known to mankind.[47],[48]

The presence of periodontitis at the time of Alzheimer’s disease diagnosis is associated with a six-fold increase in the rate of cognitive decline.

The mechanisms underlying these mouth/body/disease connections are under active investigation. With respect to Alzheimer’s disease (AD), for example, it has been known that the presence of periodontitis at the time of diagnosis is associated with a six-fold increase in the rate of cognitive decline.[49] Now, in a groundbreaking study published in 2019, an international team of scientists discovered P. gingivalis in the brains of AD patients, and showed that P. gingivalis-derived proteins, known as “gingipains”, correlated with the disease pathology.[35] Small-molecule gingipain inhibitors blocked beta-amyloid production (a hallmark of AD), reduced brain inflammation, rescued neurons in the hippocampus, and even reduced the bacterial load of P. gingivalis in animals, suggesting that gingipain is a possible drug target. Clinical trials are underway to assess whether gingipain inhibitors can be used to treat AD in humans.[50]

All these findings shed an entirely new light on the oral microbiome, and should make us sit up and take notice of our oral health.

How you can influence oral health

Good dental care is critical to keeping your oral ecosystem healthy. The American Dental Association suggests brushing your teeth twice daily, flossing once daily, and visiting a dentist at least twice yearly to remove plaque that may have accumulated. Chewing sugarless gums, including mastic gum, can help inhibit plaque formation.[51],[52]

What you put in your mouth impacts not only your general health but also that of your teeth and gums.

What you put in your mouth impacts not only your general health but also that of your teeth and gums. When you eat and drink sugary foods and beverages, you’re feeding the bacteria that cause tooth decay and periodontal disease.[53] Experts suggest limiting free sugar intake to less than 5% of total calories.[54]

Diets that include a high intake of fruits and vegetables, fiber, and dairy products are associated with a reduced risk of periodontal disease.[55] Although fresh fruit contains sugar in the form of fructose, fruit consumption is associated with low levels of dental caries.[56] Here are some foods to seek out:

  • Fiber-rich fruits and vegetables. Foods with fiber help keep your teeth and gums clean. Dietary fiber also encourages the growth of beneficial microbes in the mouth.[57]
  • Nitrate-containing vegetables. Dietary nitrates, found in vegetables such as beets and kale, induce beneficial changes in the oral microbiota,[58],[59] providing protection against mutans pathogenesis.[60],[61] Certain oral bacteria reduce nitrates to nitrites, which are then converted to nitric oxide (NO), which plays an important role in maintaining a healthy blood pressure.[62],[63]
  • Dairy products. Dietary calcium, particularly from milk and fermented products such as yogurt, may help protect against periodontitis.[64],[65]
  • Green and black teas. Green and black teas contain polyphenols that suppress harmful oral bacteria.[66]

Key nutrients for oral health

Along with good oral hygiene, adequate nutrition is essential for oral health.[67],[68],[69] Here are some key nutrients and nutraceuticals backed by research:

  • Vitamin C: A systematic review of seven human studies showed that higher vitamin C intakes were linked to a lower risk of periodontal disease.[67],[69]
  • Vitamin D: Periodontal disease is associated with vitamin D deficiency,[70] and vitamin D supplementation helps reduce the severity of periodontitis.[71],[72] Vitamin D was shown to reduce inflammation, stimulate tooth mineralization, and boost the production of antimicrobial peptides, which may help defend against the pathogens associated with oral disease.[73]
  • Curcumin: Curcumin has efficient antibacterial activity against P. gingivalis infection and biofilm formation, based on laboratory and animal studies.[74],[75],[76]
  • Berberine: Berberine, commonly used as an antimicrobial and blood sugar-balancing agent, was found to inhibit the growth of P. gingivalis, reduce gingipain activity, and increase osteogenesis (bone cell formation), suggesting that it could even help repair periodontal bone loss.[77],[78]
  • Melatonin: Melatonin, the body’s natural sleep-inducing hormone/antioxidant, may help protect against free radicals produced by inflammatory periodontal bacteria.[79] A recent clinical trial showed that melatonin supplementation (10 mg daily) was a helpful adjunct to the surgical treatment of periodontal disease.[80]
  • Hydrogen-rich water: Water enriched with hydrogen (usually generated by water ionization or the reaction of a special preparation of metallic magnesium with water) may attenuate oxidative stress and ameliorate periodontitis, according to studies in animals and humans.[81],[82],[83] In the human trial, the participants consumed one liter of hydrogen-rich water daily for eight weeks.


The link between the oral microbiome and many diseases, including Alzheimer’s, should spur us all to take care of our teeth! The oral microbiome is influenced by a multitude of factors, including age, smoking, dental hygiene, genetics, medications, diet, and nutrition. High-fiber diets that emphasize vegetables and fruits, along with adequate calcium and vitamins – especially vitamins C and D – are crucial for oral health. Select nutraceuticals, including curcumin, berberine, melatonin, and hydrogen-rich water, may also be protective.

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