Podcast episode 136 (in German)
Oral microbiome – a gum bacterium in the brain and the better reason to floss
November 13, 2026
In 51 of 53 brain samples from people with Alzheimer’s, an enzyme turned up that almost only one gum bacterium produces. This led to a big hypothesis, a halted drug and a new trial — and in the end to the better reason to floss.
What it is about
Porphyromonas gingivalis is the best-known pathogen of periodontitis, the chronic inflammation of the tooth-supporting tissue. In 2019 a paper found its enzymes and its genetic material in Alzheimer’s brains and, in mice, a remarkably complete chain leading to the plaque protein. The first trial in humans missed its primary goals and was stopped because of liver values; a successor is now testing the signal specifically where it had appeared. For the heart, too, the associations are strong, but proof of cause and effect is missing. In between, people with periodontitis speak for themselves, from the shock of diagnosis to the shame of talking about it. The conclusion: treatment is worthwhile because it preserves teeth — heart and brain would be an unproven bonus.
Key points
- 96 percent of the Alzheimer’s brain samples were positive for one of the bacterium’s enzymes, 91 percent for the other; in the cerebrospinal fluid of living patients, its genetic material was found in 7 of 10.
- In older mice infected orally for 6 weeks, amyloid beta in the brain rose; an inhibitor of the enzymes reduced the bacterial load there by up to 90 percent.
- The GAIN trial with 643 people missed both primary endpoints in 2021; only in a prespecified subgroup of 242 with the bacterium detected in saliva did the higher dose slow decline on the cognitive scale by 57 percent.
- Liver values above 3 times the upper limit of normal in 7 and 15 percent led to a halt in January 2022; the follow-up trial with 300 saliva-positive people is funded with 49.2 million dollars.
- In a trial with 120 people with severe periodontitis, vascular function was worse 1 day after intensive treatment and better after 60 and 180 days than in the comparison group.
- For heart attack and death, the Cochrane group found only 2 randomized trials in 2022, one with 165 people and one with 303, of whom 37 were followed long enough.
- One review brought together 8 interview studies with 131 affected people, a newer one 13 studies with 215: diagnosis as a shock, shame about bad breath, and after treatment usually more sense of control.
Where the data stop
In animals the Alzheimer’s finding is remarkably complete, but many authors of the foundational paper worked at the company that developed the inhibitor, and the paper states this openly. In humans, so far only a subgroup has shown a signal, and even there everyday abilities did not change; in July 2026 the follow-up trial was still recruiting participants. For the heart, the American Heart Association stated in December 2025: association yes, cause and effect not confirmed. Better vasodilation is not yet a prevented heart attack.
The interviews come from a few selected people, but they show what changes in everyday life. An analysis of 47 short videos on oil pulling found mainly enthusiasm about fresher breath; there is limited evidence for that, as an add-on, not as a replacement. Thin data are nevertheless no reason to wait here: the professional society estimates around 14 million people in Germany with severe periodontitis requiring treatment, and bleeding gums are not a sign of aging but a finding that should be looked at once.
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Published on November 13, 2026.
The topic in the database
- The mouth is the body’s second-largest microbiome. Periodontitis bacteria such as Porphyromonas gingivalis are suspected in connection with cardiovascular disease and…Oral microbiome & periodontitis
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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-09-23.