Could Your Mouth and Gut Hold the Key to a Sharper Mind?

What the latest science says about bacteria, brain health, and what you can do about it.

Most of us think of Alzheimer's disease as something that happens in the brain. Rogue protein clumps called amyloid plaques build up, brain cells die, memories fade. But a quiet revolution is taking place in dementia research — and it points somewhere surprising: your mouth. And your gut.

Researchers are discovering that the same tiny organisms living in your gums and digestive system may play a meaningful role in whether Alzheimer's disease develops at all. More importantly, these are environments we can influence — through diet, dental care, and an interesting bee (as in bumble bee) product.

This article summarizes what we currently know and offers five practical steps grounded in the emerging science.

The Surprising Link Between Bacteria and Dementia

It has been known for over a century that a specific type of bacteria — called spirochetes — can cause dementia. The bacteria that causes syphilis (*Treponema pallidum*) can, if untreated for decades, invade the brain and produce exactly the kind of memory loss, brain shrinkage, and protein deposits we associate with Alzheimer's disease today.

That historical observation has led researchers to ask a provocative question: what if other, more common bacteria — particularly those found in infected gums — could do something similar?

Swiss researcher Dr. Judith Miklossy has spent three decades examining this possibility. In a landmark 2011 study published in the Journal of Neuroinflammation*, she analyzed hundreds of brain autopsies and found that spirochete bacteria were present in more than 90% of Alzheimer's brains — and were essentially absent in healthy brain tissue. The statistical difference was enormous. She went further and argued, using a respected scientific framework called Hill's criteria, that the relationship was likely causal — not just coincidental.

The most relevant bacteria she identified weren't exotic. Many were the same Treponema species that live in unhealthy gums. Others included Borrelia burgdorferi, the bacterium behind Lyme disease.

"Spirochetal infection occurs years or decades before the manifestation of dementia. As adequate antibiotic and anti-inflammatory therapies are available, one might prevent and eradicate dementia." — Dr. Judith Miklossy, 2011

Why Gum Disease May Matter More Than We Thought

You've probably heard that gum disease is linked to heart disease. But emerging research suggests the connection to brain health may be just as significant.

The mouth is home to hundreds of bacterial species. In a healthy mouth, they coexist in balance. In a diseased mouth — with bleeding gums, deep pockets around teeth, and chronic inflammation — harmful bacteria flourish and can enter the bloodstream through those inflamed tissues.

Porphyromonas gingivalis, the primary driver of chronic gum disease, has now been found in the brains of Alzheimer's patients, with its toxic enzymes (called gingipains) sitting right alongside amyloid plaques. This finding, published in Science Advances in 2019, made headlines in the research community.

Dr. Eva Sapi at the University of New Haven has added another twist: bacteria like Borrelia burgdorferi can form protective structures called biofilms in the brain — a kind of protective slime that makes them very difficult to kill with conventional antibiotics. Her 2012 research characterized these biofilms in detail, and later work (2022) found them present along with amyloid deposits in AD brains.

The working theory: the brain's own immune system tries to fight off these bacterial invaders by producing amyloid-beta — the same protein that accumulates in Alzheimer's disease. Amyloid may actually be an antimicrobial weapon, not just a random garbage protein. But when the infection persists, the immune response never stops — and the amyloid accumulates to destructive levels.

Your Gut Has Something to Say About Your Brain

The second major frontier in this story is the gut. The human digestive system hosts trillions of microorganisms — collectively called the gut microbiome — and they communicate constantly with the brain via a two-way highway called the gut-brain axis.

This communication happens through hormones, immune signals, and the vagus nerve, which runs from the brainstem to the abdomen. When the gut microbiome is healthy and diverse, these signals tend to be anti-inflammatory and neuroprotective.

When the gut is in a state of dysbiosis — imbalance — the signals shift toward inflammation.

A 2024 review in Experimental & Molecular Medicine confirmed that the gut microbiome controls peripheral neurotransmitters, metabolites, and immune signaling in ways that directly affect Alzheimer's disease development. Studies consistently find that AD patients have a less diverse gut microbiome, with more pro-inflammatory bacteria and fewer beneficial species like Bifidobacterium and Lactobacillus.

One key mechanism: beneficial gut bacteria produce short-chain fatty acids (SCFAs), particularly butyrate, which maintain the intestinal lining, reduce brain inflammation, and protect neurons. In Alzheimer's patients, SCFA production is often reduced.

The gut and mouth microbiomes are also connected to each other — bacteria can travel from the oral cavity into the digestive system, meaning poor oral health can seed gut dysbiosis as well.

Where Propolis Enters the Picture

Propolis is a resinous substance produced by honeybees. They collect it from plant buds and tree bark and use it to seal and sterilize the hive — it's the hive's immune system. For thousands of years, traditional medicine from Egypt to Greece to South America has used it for its healing properties.

Modern research has identified over 300 bioactive compounds in propolis, dominated by polyphenols — the same broad category of health-promoting plant compounds found in green tea, berries, and dark chocolate.

What makes propolis particularly interesting in the context of dementia research is that it acts through multiple pathways simultaneously:

In the Mouth

Multiple studies have confirmed that propolis is potently antimicrobial against the exact bacteria implicated in Alzheimer's disease — including Porphyromonas gingivalis, Prevotella intermedia, and various Treponema species. A 2025 randomized double-blind clinical trial found that propolis A 2025 randomized double-blind clinical trial found that propolis toothpaste toothpaste significantly reduced periodontal pocket depth and shifted the oral environment toward a less pathogenic state.

Crucially, propolis is also active against biofilms — the same protective structures that make bacteria hard to kill in the brain. Brazilian green propolis extracts have been shown to reduce colony-forming units in preformed biofilms by more than a million-fold in laboratory studies.

Unlike conventional antibiotics, no cases of bacterial resistance to propolis constituents have been reported — a remarkable property for an antimicrobial agent.

In the Gut

Propolis polyphenols act as prebiotic-like compounds — they selectively feed beneficial gut bacteria while suppressing harmful ones. Animal studies have shown propolis treatment repairs the intestinal mucosal lining, improves gut microbial diversity, and increases production of protective short-chain fatty acids, particularly butyrate.

In the Brain

Perhaps most remarkably, propolis appears to have direct neuroprotective properties. Studies in Alzheimer's disease model mice have shown it reduces the hyperactivation of microglia and astrocytes — the brain's inflammatory cells — that drive amyloid accumulation. Early-stage administration significantly improved memory and cognitive performance in these models.

In human clinical trials, Brazilian green propolis has been shown to improve scores on standardized cognitive tests (MMSE and ADAS-cog) in elderly subjects with mild cognitive impairment, alongside measurable reductions in inflammatory markers in the blood.

A systematic scoping review of 66 published studies concluded that propolis shows "protective and therapeutic benefits in alleviating symptoms of brain and neurological disorders and injuries."

Important note: Propolis composition varies by geography and season. The best-studied variety for cognitive benefits is Brazilian green propolis (from Baccharis dracunculifolia). Most human cognitive trials used standardized extracts, not raw propolis. Dosing and long-term safety in large populations remain areas needing further study.

What This Means Right Now

To be clear: the science reviewed here is promising but still evolving. Spirochetes, oral bacteria, and gut dysbiosis are not proven singular causes of Alzheimer's disease — and propolis is not a cure. Alzheimer's is a complex condition with genetic, metabolic, and environmental contributors.

But the convergence of evidence is striking. Multiple independent research threads are pointing in the same direction: that chronic low-grade infection and inflammation — starting in the mouth and gut, decades before cognitive symptoms appear — may be meaningful contributors to the disease. And that this pathway is one we can intervene in.

The practical implications don't require waiting for pharmaceutical breakthroughs. They're available at the drugstore, the farmer's market, and the dentist's office.

5 Simple Steps You Can Take Today

1.  Treat your gum health as brain health. Brush twice daily, floss daily, and see a dental hygienist regularly. Bleeding gums are not normal — they're a sign of active infection. If you have chronic periodontitis, have it treated aggressively.

2.  Consider a propolis-based oral care product. Propolis toothpaste or mouth rinse is now available in health food stores and online. Look for products with standardized propolis extract (EEP — ethanolic extract of propolis). It's a low-risk addition to an existing oral hygiene routine.

3.  Feed your gut microbiome. Eat a diverse, fibre-rich diet with plenty of vegetables, legumes, and whole grains. Include fermented foods (yogurt, kefir, kimchi, sauerkraut). Limit ultra-processed foods, which deplete microbial diversity.

4.  Be thoughtful about antibiotics. Broad-spectrum antibiotics disrupt both oral and gut microbiomes, sometimes for months. Use them when medically necessary — but discuss the option of targeted antibiotics and microbiome recovery strategies with your healthcare provider.

5.  Ask about propolis supplementation. Brazilian green propolis supplements (standardized extract, typically 200–400 mg/day) are available and have shown promise in clinical trials for older adults with early cognitive concerns. Always consult your doctor before starting any new supplement, particularly if you take blood thinners or have bee-product allergies.

Sources & Further Reading

This article draws on peer-reviewed published research. Key sources include:

1. Miklossy, J. (2011). Alzheimer's disease — a neurospirochetosis. Analysis of the evidence following Koch's and Hill's criteria. Journal of Neuroinflammation, 8:90.

2. Miklossy, J. (2015). Historic evidence to support a causal relationship between spirochetal infections and Alzheimer's disease. Frontiers in Aging Neuroscience, 7:46.

3. Sapi, E. et al. (2012). Characterization of biofilm formation by Borrelia burgdorferi in vitro. PLOS ONE, 7(10): e48277.

4. Senejani, A.G., Maghsoudlou, J., ... Sapi, E. (2022). Borrelia burgdorferi co-localizing with amyloid markers in Alzheimer's disease brain tissues. Journal of Alzheimer's Disease, 85(2):889-903.

5. Bredesen, D.E. et al. (2018). Reversal of Cognitive Decline: 100 Patients. Journal of Alzheimer's Disease & Parkinsonism, 8:450.

6. Seo, D. & Holtzman, D.M. (2024). Current understanding of the Alzheimer's disease-associated microbiome and therapeutic strategies. Experimental & Molecular Medicine, 56:86-94.

7. Chandra, S., Sisodia, S.S. & Vassar, R.J. (2023). The gut microbiome in Alzheimer's disease: what we know and what remains to be explored. Molecular Neurodegeneration, 18:9.

8. Ito, T., Degawa, T. & Okumura, N. (2023). Brazilian green propolis prevents Alzheimer's disease-like cognitive impairment induced by amyloid beta in mice. BMC Complementary Medicine and Therapies, 23:416.

9. Asama, T. et al. (2021). Cognitive Improvement and Safety Assessment of a Dietary Supplement Containing Propolis Extract in Elderly Japanese: A Placebo-Controlled, Randomized, Double-Blind Human Clinical Study. Evidence-Based Complementary and Alternative Medicine.

10. Zulhendri, F. et al. (2021). Can Propolis Be a Useful Adjuvant in Brain and Neurological Disorders and Injuries? A Systematic Scoping Review. Nutrients.

11. Lopez-Valverde, N. et al. (2021). Effectiveness of Propolis in the Treatment of Periodontal Disease: Updated Systematic Review with Meta-Analysis. Antioxidants, 10:269.

12. Liang, X. et al. (2024). The link between gut microbiome and Alzheimer's disease. Alzheimer's & Dementia, 20:5771-5788.