When We Forget Our Oral Hygiene, We May Ultimately Forget Everything

The influence of the microbiome on brain functions and cognitive status has been intensively investigated. The chemical compounds produced by microbes and their effects on the immune system can alter brain regions and the ability to think, learn, feel, and remember. Research has shown a clear link between the composition of the gut and oral microbiome and mental states in both normal and pathological conditions. For instance, new evidence indicates that the human microbiome is increasingly associated with neurodegenerative diseases, including Parkinson's and Alzheimer's diseases.

The Oral Microbiome

The mouth hosts a unique ecosystem of microbes due to its nature as an open system. It is regularly exposed to food, beverages, external microbes, and air, resulting in dynamic shifts in microbial populations. The oral cavity contains different microhabitats, including the tongue, teeth, gingiva, palate, and saliva. The oral microbiome is highly diverse, second only to the gut microbiota, and consists of more than 700 identified bacterial species. Species of Streptococcus, Neisseria, Prevotella, Porphyromonas, Veillonella, Fusobacterium, Gemella, Haemophilus, Actinomyces, and Capnocytophaga are the most abundant microbes in the mouth. These microbes can convert dietary nitrate to nitrite, which impacts cardiovascular health and blood pressure. The oral microbiome also modulates the immune system, preventing infections despite high microbial loads.¹

The oral microbiome can reach the gut and influence its microbial composition. This phenomenon is increasingly recognized as part of the "oral-gut axis," highlighting the dynamic relationship between oral and intestinal microbial communities. The transfer of mouth microbes to the gut is facilitated when natural barriers, such as stomach acidity and bile, are compromised due to certain physiological or pathological conditions, such as those found in infants, the elderly, or as a result of specific medications. The ease with which these microbes can transfer between individuals, as well as from the environment and food, and their significant impact on gut microbiota, regarding their substantial health effects, are often neglected by the general public.

Recent Study on Parkinson's Disease

In a recent study at King’s College, London, scientists found that bacteria from the mouth can move down to the gut in people with Parkinson’s disease. These bacteria are not only harmful and disrupt the balance of gut microbiota, but they can also produce toxins that disturb this balance and lead to inflammation. This gut inflammation can send adverse signals to the brain, making memory and thinking problems worse for people with Parkinson’s. The researchers found that people with more of these harmful bacteria and toxins in their gut had more trouble with memory and thinking. These results highlight that maintaining oral and gut health, such as practicing good dental hygiene and consuming a nutritious diet, may help slow memory loss in individuals with Parkinson’s disease. Additionally, this suggests that doctors could monitor for these bacteria as early warning signs of potential brain issues in patients with Parkinson’s.²

These results potentially highlight the significance of the microbes residing in the body's cavities in mental health and disease. The brain is often considered a unique organ located in a protected chamber, separated from the rest of the body by the blood-brain barrier, and shielded from physical and environmental insults. However, despite the brain's important role in regulating and maintaining bodily functions, it is significantly influenced by bodily status and microbes, which are not truly part of the body. Today, thanks to this research, we know that the brain is not just affected by sensory and internal signals from the body. Signals from our surroundings, like the microbes living inside us, the food we eat, and the people close to us, also directly and indirectly shape how our brain works and how we think. Changes in these factors can sometimes disrupt brain function and lead to serious illnesses.

This research on the oral-gut-brain axis in Parkinson’s disease and cognitive decline suggests maintaining good oral hygiene, regular brushing, flossing, and dental checkups to reduce harmful bacteria. Additionally, a diet rich in probiotics (such as yogurt and kefir) and prebiotics (including fiber and fermented foods) is recommended to support gut health. An anti-inflammatory diet, which is high in fruits, vegetables, and omega-3 fatty acids (found in fish and nuts), while avoiding processed sugars, can also be beneficial. Furthermore, cautious use of antibiotics is advised to preserve microbiome balance. Managing stress through practices such as meditation or exercise is crucial, as chronic stress can disrupt gut bacteria. Finally, individuals with a family history of Parkinson’s disease or dementia should consider early microbiome screening, as small lifestyle changes may significantly reduce risks by improving microbial health.