I don’t talk about this as often as I probably should.
My mom had Alzheimer’s and my dad had ALS with dementia. Watching your parents slowly lose the very thing that makes them them — changes how you think about every choice you make, every single day.
The mouth-brain connection is, unfortunately, not abstract for me because I’ve lived it.
When I look at the research on Alzheimer’s and dementia, one pattern keeps surfacing: the disease process starts decades before the first symptom. The plaques that show up on a scan at 75? The cellular damage that drives them starts at 40. Maybe earlier.
The window to prevent it is now.
And here’s what most neurologists still won’t tell you — two of the most powerful things you can do to protect your brain involve your mouth.
One you do in the morning. One you do at night.
In the morning: green tea
I’ve been drinking green tea every morning for years, and the reason I keep coming back to it isn’t the caffeine. It’s a compound called EGCG.
EGCG (epigallocatechin gallate) is one of the most studied plant compounds in neuroprotection research. It crosses the blood-brain barrier.
Multiple studies now link regular green tea consumption to meaningfully lower rates of cognitive decline — the largest, a 2006 cohort study out of Japan following nearly 30,000 adults, found that people who drank the most green tea had a 26% lower risk of cognitive impairment.
But here’s the part almost nobody talks about: EGCG is also one of the only plant compounds shown to selectively inhibit Streptococcus mutans — the primary cavity-causing bacteria — without disrupting the rest of the oral microbiome.
Most things we reach for to “kill bacteria” in the mouth (mouthwashes, peroxide rinses, even certain essential oils) take a wrecking ball to the whole ecosystem. You can think of EGCG as more of a scalpel.
A healthy oral microbiome is not just about avoiding cavities. The same dysbiosis that lets pathogenic oral bacteria thrive is increasingly linked to cardiovascular disease, metabolic dysfunction, and — yes — Alzheimer’s.
P. gingivalis, the bacteria most associated with gum disease, has been found in the brain tissue of Alzheimer’s patients. The mouth-brain axis is real, and green tea works on both ends of it.
I drink this powdered green tea because of how they source and process it — triple-screened for heavy metals and pesticides, cold-extracted into crystals that dissolve instantly.
At night: magnesium
Most people take magnesium for sleep. But there is so much more to the story…
Your brain has a waste-clearance system called the glymphatic system. It’s essentially the brain’s overnight janitorial crew — and it primarily runs during slow-wave sleep. This is when your brain flushes metabolic waste products, including amyloid-beta, the protein associated with Alzheimer’s plaques.
If you’re not getting into deep slow-wave sleep long enough, that clearance doesn’t fully happen. Night after night, year after year…imagine the cumulative effects.
Magnesium is shown in clinical research to meaningfully improve slow-wave sleep architecture — not just help you fall asleep, but get you into the stage of sleep where the cleaning actually happens.
I take 500mg every night of this magnesium supplement, 1-2 hours before bed. It’s important that you choose a magnesium that is high quality and rigorously tested. Most supplements contain one or two forms at most. But magnesium is involved in over 300 enzymatic processes in the body, and different forms have different mechanisms and target tissues. Your brain, your muscles, your cardiovascular system — they each respond to different forms.
These two things — green tea in the morning, magnesium at night — also happen to support your oral microbiome in ways most people miss.
Magnesium is essential for healthy saliva production. Saliva is your mouth’s built-in defense system: it remineralizes enamel, neutralizes acid, and keeps pathogenic bacteria in check. Magnesium deficiency quietly undermines all of that. Most of us are deficient and don’t know it.
And we’ve already talked about what EGCG does for bacterial balance in the mouth.
So these aren’t just brain supplements. They’re part of a whole-body strategy that starts in the mouth.
The one other thing I’d add…
If you’re not sleeping well — really not sleeping well, and especially if you snore, wake up tired, or have been told you stop breathing at night — no supplement is going to fully compensate for untreated sleep apnea. The glymphatic system can’t do its job if your airway is collapsing overnight.
Sleep apnea is dramatically underdiagnosed in women. The symptoms present differently: fatigue, morning headaches, difficulty concentrating, waking up exhausted. If that sounds familiar, please look up a sleep specialist through AADSM.org — that’s the American Academy of Dental Sleep Medicine. They train dentists specifically in airway and sleep, and they can often help when traditional sleep doctors have missed things.
And if you haven’t worked with a functional dentist, someone trained to look at your mouth as part of your whole health picture — airway, microbiome, sleep, all of it — you can search the Functional Dentist Directory to find one near you.
My parents didn’t have any of this. They didn’t know to look for these connections. I can never be entirely sure it would have changed everything — but I think about it.
I do what I can, every morning and every night, because that’s the window I have.
I hope you use yours.
— Mark
Citations and Further Reading
The landmark study: The single most important piece of research in this space remains Dominy et al. (2019), published in Science Advances: Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors. The researchers identified P. gingivalis — the keystone pathogen in gum disease — in the brain tissue of Alzheimer’s patients. Critically, gingipain levels (the toxic enzymes P. gingivalis produces) correlated with tau tangles and ubiquitin pathology, two hallmarks of Alzheimer’s. This was the first study to propose a causal, not just correlational, link. → Read it at Science Advances
The doubled dementia risk: A 2019 retrospective cohort study using National Health Insurance data found that a diagnosis of chronic periodontitis was associated with a 95% higher risk of developing dementia — even among people who otherwise maintained healthy lifestyle habits. → Referenced in: ScienceDirect narrative review, January 2025
The MRI evidence: In 2024, researchers at Columbia University’s College of Dental Medicine, led by Dr. Panos Papapanou, published the first epidemiological study linking clinical, microbial, and serological features of periodontitis to structural MRI findings associated with Alzheimer’s disease and related dementias. This matters because it shows measurable brain changes, not just statistical risk. → Columbia University College of Dental Medicine
The systematic literature review: Villar, Paladini & Cossatis (2024), published in The Journal of Prevention of Alzheimer’s Disease, analyzed 328 documents spanning 2000–2023 and identified two primary mechanisms connecting gum disease to brain pathology: systemic inflammatory cascades and direct microbial translocation into the central nervous system. → SpringerLink
The PRISMA-guided systematic review. A 2025 systematic review published in Applied Sciences (MDPI), following PRISMA guidelines and using the ROBINS-I bias assessment tool, synthesized human studies on salivary and blood biomarkers and periodontal therapies in the context of Alzheimer’s. It concluded that periodontal disease is both a risk factor and a potential therapeutic target for Alzheimer’s. → MDPI Applied Sciences
Further reading on my website, Ask the Dentist
Can gingivitis cause Alzheimer’s disease? — My most comprehensive breakdown of the P. gingivalis research, the gingipain mechanism, and what it means practically for your gum care.
The Oral Microbiome & Its Impact on Every Other System in the Body — How oral dysbiosis connects to the gut-brain axis, cardiovascular disease, metabolic function, and more.
Interview: Why We Shouldn’t Ignore the Oral Microbiome — A conversation with researcher Cass Nelson-Dooley on the 45% bacterial overlap between the mouth and colon, and why the oral microbiome is the starting point for whole-body health.