More than 500 species of bacteria live in the mouth, but there’s one that can turn nasty, corroding the gums and decaying the teeth. It’s called Porphyromonas gingivalis.

What’s more alarming, this infection can travel from the mouth to other parts of the body such as the liver and coronary arteries. It’s a well-known risk factor for heart and artery disease. And now it’s been found in the brains of Alzheimer’s patients.

So Mom was right when she nagged you to brush your teeth. Keep reading to learn more about this possible cause of brain loss. . .

Whether the microbes come along after dementia takes hold or can actually cause the disease is not known for sure, but I’m putting my bets on the latter. Gum disease is firmly established as a cause of whole-body inflammation.

So we shouldn’t be surprised that breakthrough research now tells us P gingivalis may be an important driver of Alzheimer’s.

That makes oral hygiene a top priority for all of us.

Toxic Enzymes Harm the Brain

A 26-strong research team from a number of US universities and four other nations conducted a range of experiments in lab cultures, rodents, and in deceased and living humans. They published their findings a few weeks ago in Science Advances.

In mice, the oral infection was found to penetrate the brain and increase production of amyloid beta, the Alzheimer’s-linked protein. Most laypeople just think of it as brain plaque.

P gingivalis also produces poisonous enzymes called gingipains which have previously been linked with two other Alzheimer’s-associated proteins called tau and ubiquitin.

As readers know, I lean toward the theory that amyloid and tau proteins are an effect of Alzheimer’s, not a cause. They are the body’s response to chronic inflammation. Their increased presence in people with the gum disease microbe supports the theory that this infection affects the brain.

In examining post-mortem human brain samples, gingipains appeared in 96% of Alzheimer’s patients compared to only about half this percentage in non-demented individuals. The higher the gingipains load, the greater the amount of tau and ubiquitin.

The researchers also checked the hippocampus and cerebral cortex — two areas of the brain affected by Alzheimer’s — and found gingipains in both. P gingivalis DNA was also identified in the cerebrospinal fluid of living and deceased Alzheimer’s patients.

Having established gingipains as a good clinical target, they developed a “library” of gingipains inhibitors to try to identify the most potent. The outstanding inhibitor was called COR388.

A series of experiments in mouse models followed. These demonstrated that the inhibitor lowered P gingivalis residues in the brain, reduced neuro-inflammation, halted the production of amyloid beta, and protected neurons in the hippocampus.

Oral Health is Vitally Important

Lead author Stephen Dominy, MD believes doctors should target P gingivalis and gingipains in the brain instead of amyloid beta. I certainly agree, in view of the fact that strategies targeting amyloid have failed again and again. Amyloid is an antimicrobial agent. To repeat: it’s an effect of the infection, not the cause of dementia.

According to Dr. Dominy, “Infectious agents have been implicated in the development and progression of Alzheimer’s disease before, but the evidence of causation hasn’t been convincing.

“Now, for the first time, we have solid evidence connecting…P gingivalis and Alzheimer’s pathogenesis while also demonstrating the potential for a class of small molecule therapies to change the trajectory of [the] disease.”

He went on to say that maintaining healthy gums and teeth is important in reducing P gingivalis. He thinks this should be taken far more seriously than it is. Once the gum disease microbe is established in the brain, it’s too late. No amount of good oral hygiene will help, so prevention is key.

Professor Clive Ballard, Executive Dean of Medicine at the University of Exeter, England, and a leading expert in dementia, was asked to comment on the findings:

“The study further supports a key link between oral health and dementia, suggesting that it isn’t simply an association but highlights a potential mechanistic link that the bacteria may be directly acting on processes in the brain relevant to Alzheimer’s disease.

“But perhaps more importantly, this study highlights the importance of oral health, and that this should be a much higher public health priority, especially in older people.”

If you’ve never encountered a dental hygienist, it’s time to do so. She will tell you the proper way to brush and floss (or, better yet, use one of those water devices), and will also recommend a good antimicrobial mouthwash.  There are a number of natural, nontoxic ones on the market. In my experience, the mouthwash is more important than the brushing in getting rid of bacteria.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357742
  2. https://www.medicalnewstoday.com/articles/324298.php

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