The findings, published in the journal Nature Communications, indicate that communication between the gut and the brain helps strengthen memories after eating nutritious food, while long-term consumption of unhealthy diets may weaken this process.
The research was led by scientists at the University of Southern California, who investigated how the vagus nerve, a major communication pathway between the gut and the brain, influences memory formation.
Using rats in laboratory experiments, the researchers found that nutrient-rich foods triggered the release of acetylcholine, a neurotransmitter that plays a critical role in learning and memory. The increase occurred only when signals from the gut reached the brain through the vagus nerve.
When researchers blocked the vagus nerve, the animals struggled to remember where they had previously found food, suggesting that gut signals are essential for forming certain types of memories.
The study also found that the brain responded to the nutritional value of food rather than its taste alone. Rats that consumed foods containing nutrients, such as sugar or fat, showed stronger memory-related brain activity than those given sweet-tasting drinks with little or no nutritional value.
According to the researchers, this mechanism may have evolved to help animals remember the locations of reliable food sources, improving their chances of survival by encouraging them to return to places where they previously found nutritious meals.
However, the benefits appeared to diminish with long-term unhealthy eating habits. Rats fed diets high in fat and sugar early in life later showed weaker communication between the gut and the brain, even after returning to healthier diets. They also performed worse in memory tests involving food locations.
The researchers say the findings could help explain why obesity, poor nutrition and metabolic diseases such as diabetes are often associated with an increased risk of cognitive decline. The study points to disrupted gut-to-brain communication as one possible biological link.
The discovery may also have implications for neurodegenerative diseases. The researchers noted that reduced acetylcholine activity in the hippocampus is one of the earliest changes observed in Alzheimer’s disease, raising the possibility that therapies targeting the vagus nerve could one day help support memory and cognitive function.
While the experiments were conducted in animals, scientists say more research is needed to determine whether the same process occurs in humans. Even so, the findings provide fresh insight into the close relationship between the gut and the brain and could open new avenues for treating memory disorders in the future.
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