Alzheimer's and gum bacteria: what the 2019 study really found

The Alzheimer's mouth bacterium: what's real and what's business

A headline like "90% of Alzheimer's cases are caused by a mouth bacterium" is perfect for scaring people and for selling. The reality published on 23 January 2019 in Science Advances is different: the study by Dominy and colleagues detected the bacterium Porphyromonas gingivalis and its toxins (gingipains RgpB and Kgp) in the brains of Alzheimer's patients, but the percentages fall far short of the rounding in the viral message. 96% of brains with the disease tested positive for RgpB (51 of 53) and 91% for Kgp (49 of 54), with loads clearly higher than in controls without dementia. Correlation is not causation, and here it's worth separating the finding from the wishful thinking.

The mechanism: from gums to brain

The hypothesis is neither new nor far-fetched: Porphyromonas gingivalis is the main bacterium behind chronic periodontitis, and it has been found in the brains of deceased Alzheimer's patients. The gingipains it secretes degrade neuronal proteins and, according to some research, interfere with beta-amyloid protein, which would act as a defence against neurotoxins. The problem: later studies published on PubMed Central and MDPI explore the pathway further, but they don't close the causal chain. The bacterium being in the brain doesn't prove it arrived before the dementia or that it is its sole cause.

The chewing gum, the chlorella and the prevention business

Anyone looking for the solution on social media will find more marketing than science. In the same environment where the headline circulates, a chewing gum is promoted with a purchase link and discount code; oil pulling, chlorine dioxide and chlorella as a metal chelator are also touted. As for aluminium as a cause, studies have been debunking it for decades, and blaming it for Alzheimer's is part of folklore. The only recommendation with real backing is oral hygiene: treating periodontitis reduces bacterial load and may be a preventive factor, not a miracle cure.

What's still missing: causation and diagnosis

Alzheimer's diagnosis is still clinical and, in many cases, confirmed post mortem; MRI scans can't see the bacterium. Lacking validated biomarkers, the leap from "association" to "cause" is enormous. Meanwhile, this has been known since 2019 and the treatment hasn't arrived. The uncomfortable question is why so much energy goes into selling chewing gum and so little into making periodontal health a health priority. The study opens a promising avenue; turning it into a catchy headline and a discount code is another matter.

We've known since 2019, the biomarkers are there and the chewable industry is already out selling its solution. What remains unanswered is why a hypothesis with so much potential hasn't turned dental hygiene into health policy. Does it take a discount code to believe it?