Recent research shows that the tiny organisms living in our mouths may play an important role in how our brains work as we get older. Our mouths are home to many different types of bacteria, a community scientists call the oral microbiome.
This study suggests that the balance of these bacteria can affect our thinking, memory, and overall cognitive function. The findings also point to a simple idea: changing our diet to include more nitrate-rich foods may help delay the decline in brain function that often comes with aging.
Many older adults suffer from mild cognitive impairment (MCI), a condition that causes problems with memory and thinking but is not as severe as dementia. About 15% of older adults have MCI, and this condition is known to be a major risk factor for developing more serious brain diseases like Alzheimer’s.
There is also a well-known link between gum disease (periodontitis) and poorer brain function. Gum disease causes inflammation in the mouth, and this inflammation might lead to problems in other parts of the body, including the brain.
In this study, researchers led by Anni Vanhatalo examined the mouths of 115 people. Of these, 55 participants were diagnosed with mild cognitive impairment, while the rest were considered healthy.
The researchers collected samples from the participants’ mouths to study the types and amounts of bacteria present. Their goal was to find out if there was a connection between certain bacteria and cognitive abilities.
The study proposed two ways that the bacteria in our mouths might affect our brains. One possibility is that harmful bacteria could enter the bloodstream and travel to the brain, causing damage along the way.
The other possibility is that these harmful bacteria might push out the good bacteria that help produce a substance called nitric oxide. Nitric oxide is very important for brain health because it helps brain cells communicate with one another—a process that is crucial for learning and memory.
The researchers found that people with mild cognitive impairment who had higher amounts of bacteria from the group called Neisseria tended to perform better on tests of planning and visual attention. In healthy individuals, more Neisseria was linked with a stronger working memory, which is the ability to hold and use information over short periods.
On the other hand, a high level of bacteria from the group called Porphyromonas was more common in people with mild cognitive impairment. The study also noted that a type of bacteria known as Prevotella intermedia was more often found in people carrying the APOE4 gene. This gene variant is known to increase the risk of cognitive decline and Alzheimer’s disease.
Diet plays an important role in this relationship. What we eat can change the mix of bacteria in our mouths. Diets that are rich in nitrates—found in many vegetables and foods recommended in the Mediterranean or DASH (Dietary Approaches to Stop Hypertension) diets—can encourage the growth of good bacteria.
These bacteria help produce nitric oxide, which supports brain functions such as the ability of brain cells to adjust their connections, a process known as synaptic plasticity. When the brain has enough nitric oxide, it works better, especially when it comes to learning and forming memories.
This study offers a new look at the connection between oral health and brain health. It suggests that keeping a healthy balance of bacteria in the mouth may be one way to support cognitive function as we age. In addition, it points to the possibility that simple dietary changes or the use of prebiotics—substances that help good bacteria grow—could be effective in delaying cognitive decline.
In reviewing these findings, it is clear that our mouth bacteria may have more influence on our brain than previously thought. The research shows that some types of bacteria are linked to better memory and attention, while others are associated with cognitive problems.
This insight gives us hope that by taking care of our oral health and choosing a diet rich in nitrates, we may be able to slow down the decline in brain function that comes with age.
However, more long-term research is needed to confirm these relationships and to understand exactly how the oral microbiome affects cognitive health. Overall, the study provides valuable evidence that supports the idea of simple, lifestyle-based interventions to help maintain brain health as we grow older.
The research findings can be found in PNAS Nexus.
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