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Periodontitis is another word for gum disease, caused by a specific bacteria called Porphyromonas gingivalis, that leads to infection of the tissue holding the teeth in place, and as a consequence, symptoms such as bleeding gums and loose teeth.
The association between chronic gum disease and cognitive impairment has long been established, with several studies showing a strong correlation between periodontitis and Alzheimer’s disease. In 2009, a cross sectional observational study on participants of 60 years and over, tested 2355 people for IgG antibodies to P. gingivalis. Those who had the highest levels of IgG antibodies, were more likely to have poor delayed verbal recall and impaired subtraction, compared to those with the lowest. This is significant, as we know that the presence of IgG antibodies demonstrates that the body has created an inflammatory response to the bacterium, which is strongly associated with the pathogenesis of Alzheimer’s disease.
We already know that patients with Alzheimer’s disease exhibit neuroinflammation that is akin to a reaction to an infectious agent, like bacteria, leading to the activation of the brain’s immune cells called the microglia, as well as a cascade of cytokine production – another hallmark of inflammation. For this reason, infectious agents have been robustly studied as a key contributing factor to the development of Alzheimer’s. However, a direct causal role is yet to be established.
Despite the lack of evidence for a causative role, associations between cognitive decline and bacterial infection have continued to be established. In another more recent study, published in Alzheimer’s Research & Therapy in August 2017, where more than 25,000 people aged 50 or older participated, researchers found that people who have suffered from gum disease for 10 years or longer are 70% more likely to develop Alzheimer’s disease. This study also highlighted that in those with chronic gum disease, there was a higher prevalence of depression, traumatic brain injury and hyperlipidaemia, which may all be contributors in the development of dementia. This research suggests that there may be various factors at play, rather than just gum disease on its own.
The bacteria responsible for the infection is not only found in those with gum disease, but has also been found at low levels in 25% of healthy individuals with no presence of oral disease. However, what more recent studies are showing is that it is the proteins called gingipains, that are released by the bacteria that are responsible for damage to nerve cells in the brain, rather than just the bacteria on its own. During experiments carried out in mice that were infected orally by P.gingivalis, scientists discovered that they later demonstrated signs of brain deterioration and infection, which are concurrent with humans showing symptoms of early-stage dementia.
In this same study, carried out by researchers from a variety of universities, brain tissue samples from approximately 100 people with and without Alzheimer’s were analysed and tested for two different types of gingipain proteins. They also tested for the presence of gingipain DNA in both the cerebrospinal fluid and the saliva of people that had been diagnosed with Alzheimer’s. What they found was that the level of gingipains in brain tissue of those with Alzheimer’s was between 91% and 96% (for the two different proteins), in comparison to 39% and 52% in those without Alzheimer’s. Furthermore, they found gingipain DNA in 7 out of 10 cerebrospinal fluid samples in those with Alzheimer’s and 10 out of 10 for the saliva samples.
P.gingivalis has, in addition, been shown to be extremely virulent – unlike other bacteria, studies demonstrate that broad-spectrum antibiotics rarely eradicate it and may lead to resistance to it. In addition, P.gingivalis depends on the secretion of gingipains to maintain its survival. They do this by supporting the bacteria’s colonization and the inactivation of the host’s immune defences. Whilst drugs have been developed to block the neuroinflammatory action of gingipains, trials have yet to be completed on humans to assess the efficacy of them.
Researchers from the University of Central Lancashire in the UK, report that bacteria like P.gingivalis can enter from oral cavities into the bloodstream through a variety of daily activities, such as eating, brushing teeth and chewing. However, they mention in a study published in the Journal of Alzheimer’s Disease, that the bacteria is more likely to enter the circulatory system after invasive dental treatment, which then goes on to trigger inflammation. Dr. Sim K. Singhrao, Senior Research Fellow at UCLan said: “we are working on the theory that when the brain is repeatedly exposed to bacteria and/or their debris from our gums, subsequent immune responses may lead to nerve cell death and possibly memory loss.”
Whilst we know that having dementia can lead to difficulties maintaining daily habits like brushing teeth properly, the findings of many studies suggest that gum infections precede the diagnosis of dementia. This means that, like other modifiable risk factors such as diet, smoking, obesity and diabetes, there are things that we can do to help reduce the chance of developing Alzheimer’s disease.
Besides from the obvious dental hygiene habits like brushing teeth and the tongue after every meal to remove food and plaque, flossing and using an antibacterial mouthwash, there are also dietary measures that can be put in place to offer extra support.
For example, research shows that there is a strong association between type 2 diabetes and periodontal disease. This may be due to the fact that increased levels of glucose in the blood, due to insulin resistance, can favour the growth of certain species of bacteria such as P.gingivalis. In addition, diabetes can lead to a malfunctioning of the immune system, which leads to a decrease in antibody function and therefore more opportunity for bacterial infection.
On that basis, it is therefore essential to avoid sugar, in all its forms, including the seemingly ‘natural’ alternatives to regular cane sugar, as well as focusing on a diet that helps to stabilise blood sugar levels.
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2. Avoid fruit juices and in particular shop-bought fruit juices, which often contain fruit concentrates. Whilst fruit is a natural form of sugar, fruit juices often contain the juice of the fruit without its pulp or fibre. This means that it is very quickly converted into glucose (sugar) in the body, which leads to blood sugar imbalances and eventually insulin resistance, if consumed too frequently.
3. Eat a diet that mainly consists of foods in their natural form, paying attention to meals that prioritise protein such as in pulses, eggs, poultry, meat and fish, along with a wide variety of vegetables and healthy fats found in nuts and seeds, avocado and extra virgin olive oil.
4. Switch refined carbohydrates for complex carbohydrates – these are foods that are naturally high in fibre such as whole grains like brown rice, wholemeal bread, quinoa and oats, as well as starchy vegetables like beetroot, sweet potatoes, carrots, pumpkin and butternut squash.