New research suggests that bacteria in your mouth and on your tongue may be connected to changes in brain function as you age.
A study led by the University of Exeter found that certain bacteria were associated with better memory and attention, while others were linked to an increased risk of Alzheimer’s disease.
The researchers identified two possible ways these bacteria may impact brain health. One possibility is that harmful bacteria enter the bloodstream directly, potentially damaging the brain. Alternatively, an imbalance between beneficial and harmful bacteria may reduce the conversion of nitrate—abundant in vegetable-rich diets—into nitric oxide, a chemical essential for brain communication and memory formation.
Key Findings: Beneficial and Harmful Bacteria
Individuals who had large numbers of the bacteria groups Neisseria and Haemophilus had better memory, attention, and ability to do complex tasks. These people also had higher levels of nitrite in their mouths.
On the other hand, greater levels of the bacteria, Porphyromonas, was more common in individuals with memory problems. Whereas the bacterial group Prevotella, was linked to low nitrite, which the researchers predict could in turn could mean poorer brain health and was more common in people who carry the Alzheimer’s Disease risk gene, APOE4.
The study was supported by Wellcome and part funded by the National Institute for Health and Care Research (NIHR) Exeter Biomedical Research Centre. poses an interesting possibility for early identification and intervention.
Lead author Dr Joanna L’Heureux, of the University of Exeter Medical School, said: “Our findings suggest that some bacteria might be detrimental to brain health as people age. It raises an interesting idea for performing routine tests as part of dental checkups to measure bacterial levels and detect very early signs of declining brain health.”
Mild Cognitive Impairment and Dementia Risk
While a decline in memory and brain functions is typical in old age, deteriorations in mental capabilities that are greater than would be expected with normal aging is known as Mild Cognitive Impairment. Approximately 15% of older adults fall into the category of mild cognitive impairment, considered the greatest risk factor for the development of dementia or Alzheimer’s disease.
Published in PNAS Nexus, the study recruited 110 participants, over the age of 50 from an online study called PROTECT that tracks the brain health of more than 25,000 middle-aged people in the UK. Researchers split participants into two groups: those with no brain function decline and those showing Mild Cognitive Impairment. The participants in these two groups sent in mouth rinse samples that were then analyzed and the bacteria population was studied.
Co-author Professor Anne Corbett, of the University of Exeter Medical School, said: “The implication of our research is profound. If certain bacteria support brain function while others contribute to decline, then treatments that alter the balance of bacteria in the mouth could be part of a solution to prevent dementia. This could be through dietary changes, probiotics, oral hygiene routines, or even targeted treatments.”
Reference: “Oral microbiome and nitric oxide biomarkers in older people with mild cognitive impairment and APOE4 genotype” by Joanna E L’Heureux, Anne Corbett, Clive Ballard, David Vauzour, Byron Creese, Paul G Winyard, Andrew M Jones and Anni Vanhatalo, 28 January 2025, PNAS Nexus.
DOI: 10.1093/pnasnexus/pgae543
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2 Comments
I think It’s all nutritional habits and life style. My grandparents ate 3 meals a day. And they had a few bad habits but they lived a long life and had clear minds. They went to bed at 9:pm at we’re up at 6;am every day. They we’re poor farmers. They also had plenty of exercise. They had some struggles but their minds were clear. And they died in mid 90’s
I completely agree with you. People need to realize that fresh air, eating wholesome foods, and getting exercise, are very key factors in healthy living into one’s 90s and beyond. I think a wall balanced diet is essential and the most important thing throughout our lives is that we eat real food and homemade food not stuff out of a jar a can or a box made with a bunch of powders and fillers. So many people on keto diets freak out when they see someone having oatmeal and berries and bananas and apples. They fail to realize that at least they’re eating whole food and not garbage. Obviously if someone was 500 lb this may be an issue but for most normal people, a breakfast of oatmeal berries bananas is a good start and a whole lot better than stopping off at McDonald’s for an egg mcmuffin. By and large, getting back to basics is going to be important especially for our youth. Can you imagine what the health situation will be like in 40 years when all of these generations z gamers are old and haven’t had a stitch of exercise, fresh air, or social communication? Imagine the level of dementia and Alzheimer’s and disease when the only thing they have been doing is playing video games and drinking energy drinks. The other issue is a life that is off-kilter due to excessive pornography viewing on the internet and lack of social skills and social contact. This is bad for anyone but imagine these young people in our current generation. I have a nephew that plays video games from the time he comes home from school until 3:00 in the morning. He acts like a zombie and is not out of high school yet. He has no friends no social communication his diet consists of mac and cheese and energy drinks. It’s going to be a disaster when this generation gets older.