Gut bacteria can travel to mouse brains via the vagus nerve after high-fat diet
Mar 13th 2026
A PLOS Biology study shows live gut microbes can move into mouse brains along the vagus nerve when a high-fat diet weakens the intestinal barrier, with implications for gut-driven mechanisms in neurological disease but key limitations remain.
- Researchers fed mice a high-fat Paigen diet that caused intestinal permeability and shifted gut bacterial communities.
- Live bacteria were found in the brains and genetically matched gut microbes while blood tests showed no bacteremia.
- Identical bacterial DNA was detected in the vagus nerve, and severing a cervical vagus branch sharply reduced brain bacterial levels.
- A barcoded Enterobacter strain introduced to the gut was later recovered from brain tissue, proving direct gut to brain translocation.
- Returning mice to a normal diet repaired the gut lining and removed detectable brain bacteria, indicating the effect is reversible.
- Mouse models of Alzheimer’s, Parkinson’s, and autism showed gut leakage and gut bacteria in the vagus nerve and brain even without the experimental diet.
- Limitations include that the work used only mice, brain bacterial counts were very low, the diet was an extreme formulation, and no visual imaging of bacteria in brain tissue was shown.
- The study suggests the gut could be a therapeutic target for some brain conditions, but applicability to humans is not yet established.