How Your Oral Microbiome Influences Your Risk for Dementia

• Framework of the study — The study involved 115 participants over 50 years old from the PROTECT study, an online cohort created to track the cognitive function of older adults across the United Kingdom.⁴ Saliva samples were collected from the participants, 52% of whom had healthy brain function, while 48% showed early signs of decline in memory and other brain functions.⁵

• Pathogenic bacteria increase your risk — After analysis, the study found that participants with higher levels of Prevotella intermedia — a bacterium commonly associated with gum disease⁶ — were more likely to experience cognitive impairment.⁷

• Beneficial bacteria lower your risk — In contrast, beneficial bacteria like Neisseria and Haemophilus were more abundant in those with better cognitive function. Interestingly, participants with the APOE4 gene had a distinct oral microbiome composition compared to non-carriers, highlighting a genetic aspect that influences dementia risk in this context.

• Higher NO leads to better brain health — In an article published in The Conversation, co-author Joanna L’Heureux, Ph.D. explained that,⁸ “People who had large numbers of two groups of bacteria called Neisseria and Haemophilus performed better in brain health tests.

In particular, people with these bacteria had better memory, and better ability to pay attention and perform complex tasks. These people also had higher levels of the ion nitrite in their mouths. Nitrite is made by bacteria when they break down nitrate, which is a natural part of a vegetable-rich diet.”⁹

• Bacteria have the ability to produce NO — According to L’Heureux, “Bacteria can also break down nitrite to produce nitric oxide, which improves circulation, including blood flow to the brain. This suggests that eating lots of nitrate-rich vegetables, such as leafy green spinach and rocket, could boost levels of healthy bacteria and help improve brain health, which might be especially important as people age.”¹⁰

• The risks of having low NO levels — As noted in the PNAS Nexus study, poor NO levels have been linked to conditions like hypertension and stroke, both of which are known to increase dementia risk.

According to the researchers, “During aging, endogenous NO production is reduced through decreased NOS gene expression and increased degradation of arginine, catalyzed by arginase, which is associated with cardiovascular diseases such as hypertension and risk of vascular Ad (Alzheimer’s disease).”¹¹

• Decline takes years to happen — The researchers stress that the decline of oral health takes years, or even decades, before noticeable dementia symptoms appear. As noted in the PNAS Nexus study, the Prevotella strain acts as a pathogen that induces periodontitis, which, in turn, is implicated in the development of Alzheimer’s disease and cognitive impairment.¹²

Furthermore, antibodies produced against Prevotella bacteria have also been linked to Alzheimer’s disease, according to a 10-year follow-up study the researchers cited.¹³

• APOE4 gene lowers beneficial oral bacteria — Carriers of this gene had significantly lower levels of Neisseria. At the same time, their mouths harbored higher amounts of Prevotella intermedia. In addition, APOE4 carriers are also at risk for atherosclerosis, hypertension and skeletal muscle weakness. NO deficiency is also associated with these conditions.¹⁴

• Your blood-brain barrier is compromised — Chronic inflammation, driven by an imbalanced oral microbiome, has been shown to weaken the blood-brain barrier. This allows harmful bacteria and their metabolic byproducts to infiltrate the brain, triggering immune responses that accelerate neurodegeneration. And according to the researchers, the APOE4 gene “has been associated with weakening of the blood-brain barrier.”¹⁵

• How oral pathogens affect brain health — According to the authors, “The oral bacteria gain access to the circulatory system and then relocate to the brain by traversing the blood-brain barrier, which is increasingly permeable in Ad. Known oral disease-causing bacteria have been found in the cerebrospinal fluid of patients with a brain abscess, and P. gingivalis has been discovered in the brains of patients with Ad.”¹⁶

• Oral pathogens also enter other organ systems — In addition to crossing the blood-brain barrier, the authors noted that, “The oral bacteria may also indirectly affect the brain by impairing the oral mucosal barrier and allowing metabolites produced by the oral bacteria to enter the circulatory system or exacerbating inflammation through the overproduction of cytokines.”¹⁷

1. Increase your intake of nitrate-rich foods — Certain bacteria in your mouth convert nitrates from food into NO. To ensure optimal production, make sure to eat foods high in natural nitrates like beets, arugula, spinach and celery. Furthermore, eating these foods in their natural form, rather than juicing them, will help maximize their nitrate-producing effects.

2. Cut out processed sugars and refined carbs — Harmful bacteria living in your mouth thrive on refined sugar.¹⁸ If you regularly eat or drink sugary foods, your oral microbiome will eventually become imbalanced. To get your oral microbiome back on track, swap out sugary snacks for real whole foods, such as fruits and vegetables.

3. Brush your teeth twice a day — Brushing and flossing aren’t just about keeping your breath fresh — these habits also influence the balance of bacteria in your mouth. Use a soft-bristled toothbrush and focus on your gumline, which is where harmful bacteria tend to accumulate.

It’s also wise to floss regularly, as forgetting this habit leaves behind food particles that feed pathogenic bacteria. For a more detailed look on how to brush and floss properly, read my article “Poor Oral Health Wreaks Havoc on Your Heart and Brain.”

4. Breathe through your nose, not your mouth — Breathing through your mouth reduces saliva production, which is not only important for the proper digestion of food, but also helps maintain a healthy oral microbiome. To counteract this issue, make a conscious effort to breathe through your nose. If nasal congestion makes this difficult due to issues such as allergies, address the root cause right away.

For more information on how your breathing affects your health, read “Top Breathing Techniques for Better Health.”

5. Ditch antibacterial mouthwashes that kill good bacteria — If you use a mouthwash that claims to “kill 99.9% of germs,” you are wiping out both the good and bad bacteria in your mouth. This disrupts NO production and weakens your body’s ability to produce this beneficial compound. Instead, I recommend oil pulling, which is a great way to eliminate oral pathogens.

• Oil pulling has a rich, storied history — While oil pulling might sound like a new trend, it’s actually an ancient technique rooted in traditional Indian folk medicine. I highly recommend you add this to your routine as it helps reduce your risk of tooth decay, bad breath and other oral conditions. Having said that, what oil is the best one to use? I generally recommend high-quality coconut oil, as it has natural antibacterial properties.¹⁹

• How to do oil pulling properly — Simply measure out a tablespoon of coconut oil and place it in your mouth. Thoroughly swish it using your cheeks and tongue, making sure it’s pulling between your teeth. To avoid muscle fatigue in your jaw muscles, relax them as you swish the oil, and make sure not to swallow it. You’ll know you’ve pulled correctly when the coconut oil becomes thick and milky white, signifying that bacteria has accumulated.

• Don’t rush oil pulling — Swish for 20 minutes to get the best results. If you get the urge to swallow while pulling, just spit out the oil and start again. After you’re done, spit the oil into the garbage bin or in your yard (but not on your plants). Don’t spit it in your sink, as it may coat your drainage and lead to plumbing problems.