You probably don't think much about what lives on your tongue. Most of us only notice it when it is coated in the morning or when a dentist asks us to stick it out. But the tiny world up there may matter more than it looks.
A new study in PLOS One suggests that the mix of bacteria on the tongue is linked to how quickly people think. People with more of one microbe, called Prevotella histicola, had faster reaction times on cognitive tests.
The research is early. It looked at just 60 adults in two cities, so it cannot prove that these bacteria make the brain faster. But it is the latest sign that the mouth, like the gut, may be part of the story of brain health.
What the researchers found
Scientists at the University of Exeter and Vrije Universiteit Brussel recruited 15 younger and 15 older adults in each city. They swabbed the top of each person's tongue, took blood and saliva, and ran a battery of 10 cognitive tests.
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One microbe kept standing out. People with more Prevotella histicola on their tongue reacted faster on certain tasks.
The tasks that lit up differed by country. In the UK group, it was abstract matching and line orientation. In the Belgian group, it was a visual object learning task.
Age itself was the strongest predictor of how well people performed. Older adults scored lower on tests of processing speed, no matter which city they lived in.
How mouth bacteria might reach the brain
The mouth is home to hundreds of bacterial species, and the tongue carries one of the densest patches. Some of these bacteria do more than cause bad breath. They turn nitrate from foods like leafy greens and beets into nitrite.
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The body then converts nitrite into nitric oxide, a signaling molecule that helps blood vessels widen and that the brain uses for communication between nerve cells.
According to a report in ScienceAlert, the new work did not show that this process was behind the pattern the team saw. It is a plausible mechanism, not a proven one.
What this does not mean
The authors are careful. With only 30 adults per country and uncontrolled diets, they say the findings should be treated as exploratory. Larger studies are needed to tell whether these patterns reflect real biology or statistical noise.
The study cannot say whether cleaning the tongue, using mouthwash or any other oral habit will slow cognitive aging. It also cannot say whether a shift in these bacteria predicts future decline.
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The next step, the authors note, is larger studies in more diverse groups. The goal is to see whether a specific bacterial signature on the tongue can predict future cognitive change, or whether shifting it can protect the brain.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.