What your mouth reveals about your brain: a surprising link to memory problems

What your mouth reveals about your brain: a surprising link to memory problems

Dementia is a growing problem, especially now that the population is aging. In the Netherlands, one in five people will be affected by it, and that number is even higher among women. While scientists worldwide are searching for ways to reduce the risk of this devastating brain disorder, new research points to an unexpected source of information: your mouth.

A look into your saliva

Researchers from the United Kingdom have examined the composition of bacteria in the saliva of people aged fifty and older. What they found is interesting, to say the least: people with good cognitive health appeared to have different types of oral bacteria than people whose memory was already starting to falter.

In particular, certain 'good' bacteria were found more frequently in participants who scored high on memory tests. These bacteria play a role in the breakdown of nitrate – a substance commonly found in leafy greens such as spinach and beetroot. Carbon monoxide is released during this process, which affects blood flow to the brain. In other words: what you eat influences not only your body, but possibly also your brain through your mouth.

What if you have fewer good bacteria?

In participants with lower cognitive scores, researchers found bacteria specifically linked to gum inflammation and impaired carbon monoxide production. This, in turn, affects blood flow to the brain. One of these bacteria was even found more frequently in people with a genetic predisposition to Alzheimer's. Although the precise role of these microorganisms still needs to be investigated further, there does indeed appear to be a link between oral health and brain health.

More than just cleaning

The lead researcher emphasizes that these findings could open up new possibilities. Who knows, perhaps in the future dentists will be able to help detect early signs of memory loss. According to her, it is important to take oral health more seriously: “We now know that it has more influence than just fresh breath or white teeth.”

What can you do yourself?

Although there is no conclusive evidence yet that poor oral health causes dementia, indications are mounting that it may indeed have an influence. Previous studies have already shown that people with gum problems are more likely to experience cognitive decline. This new research adds an extra dimension to this: it identifies specific bacteria that may play a role.

Nutrition proves to be an important factor in this. Healthy eating habits, with plenty of fruits and vegetables, contribute to a balanced bacterial ecosystem in the mouth. At the same time, sugar, fat, and alcohol can actually have a counterproductive effect. And of course, it remains important to brush properly, floss, and visit the dentist regularly. Smoking and vaping can disrupt the balance of the microbiome and thereby put your brain health under pressure as well.

What awaits us?

The oral microbiome has not been studied nearly as extensively as that in the gut. There is therefore still much to learn. The researchers now want to investigate further whether, for example, drinking nitrate-rich beetroot juice can have a direct effect on brain function in the elderly – via the bacteria in the mouth.

One thing already seems clear: whoever takes good care of their mouth might also be doing their memory a favor.

1. The oral microbiome and cognitive decline

Study: "Oral microbiome and nitric oxide biomarkers in older people with mild cognitive impairment" (January 2025) OUP Academic+1Taylor & Francis Online+1

Insights: This study investigated the interactions between the oral microbiome, nitric oxide biomarkers, and cognitive functions in 60 participants with mild cognitive impairment and 60 healthy controls. The results suggest that specific bacterial profiles in the mouth are associated with cognitive performance. OUP Academic

2. Porphyromonas gingivalis and neurodegenerative diseases

Study: "Porphyromonas gingivalis: a potential trigger of neurodegenerative diseases" (March 2025) Frontiers

Insights: This review summarizes how the bacterium P. gingivalis , known for periodontitis, may be involved in the development of neurodegenerative disorders such as Alzheimer's disease. The bacterium and its toxins have been found in the brains of Alzheimer's patients, suggesting a possible causal relationship.

3. Periodontitis and cognitive decline

Study: "Association between Periodontal Disease and Cognitive Impairment" (March 2023) PubMed+1ScienceDirect+1

Insights: This systematic review analyzed multiple studies and found consistent evidence for an association between periodontitis and cognitive decline or dementia. Although the exact mechanisms are still unclear, the results emphasize the importance of oral health for cognitive functions.

4. Lactobacilli as possible protection against Alzheimer's

Study: "Protective effects of a lactobacilli mixture against Alzheimer's disease" (November 2024)Nature

Insights: An animal study demonstrated that a mix of lactobacilli bacteria could prevent the negative effects of P. gingivalis on both the gums and the brains of rats. This suggests that probiotics may play a potential role in the prevention of Alzheimer's-related pathologies.Nature

5. Oral health and dementia risk

Study: "Periodontal health, cognitive decline, and dementia: A systematic review and meta-analysis" (September 2022) AGs Journals+1PubMed+1

Insights: This meta-analysis found that poor periodontal health and tooth loss increase the risk of both cognitive decline and dementia. However, the authors emphasize that further research is needed to draw definitive conclusions. PubMed+1AGs Journals+1