A team at Emory University published a study in PLOS Biology in March using mouse models to examine how diet affects the gut–brain connection. The researchers note that the gut contains more than 100 million neurons and is sometimes called a "second brain". The experiment focused on a high-fat Paigen’s Diet given to germ-free mice for nine days.
The diet altered the gut microbiome and increased intestinal barrier permeability, often called a "leaky gut". This leakage let live bacteria travel from the intestine to the brain along the vagus nerve. In one experiment the team gave mice antibiotics for three days and then introduced an engineered, barcoded Enterobacter cloacae strain with a DNA sequence not normally found in nature.
When mice ate the high-fat diet, the barcoded strain appeared in the vagus nerve and the brain, but not in the blood or other organs. Bacterial loads in the brains were low, within the hundreds, and investigators used strict procedures to prevent cross-contamination; they say the levels rule out sepsis or meningitis. The team also found low bacteria levels in mouse models of Parkinson’s and Alzheimer’s and calls for more research on diet and human neurological health.
Difficult words
- microbiome — all the microbes living in one place
- permeability — ability to allow substances to pass throughintestinal barrier permeability
- vagus nerve — nerve connecting the gut and the brain
- antibiotic — drug that kills or stops bacteria growthantibiotics
- engineer — change or design something using scientific methodsengineered
- germ-free — without germs or other microbes present
- leaky gut — condition when the intestinal barrier allows things to leak
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How might a high-fat diet change a person’s gut microbiome? Give simple reasons.
- Why do you think researchers gave antibiotics before introducing the engineered bacteria?
- What could low levels of bacteria in the brain mean for human health? Give your opinion.
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