Study lead author Devin Wahl, a PhD candidate at the University of Sydney in Australia, said: "There are currently no effective pharmaceutical treatments for dementia - we can slow these diseases, but we can't stop them - so it's exciting that we are starting to identify diets that are impacting how the brain ages."
The research, published in the journal Cell Reports, shows for the first time that unrestricted low-protein, high-carb diets have similar protective benefits for the brain as calorie restriction, which is known for its longevity benefits although not sustainable in humans.
Mr Wahl said: "We have close to 100 years of quality research extolling the benefits of calorie restriction as the most powerful diet to improve brain health and delay the onset of neurodegenerative disease in rodents.
"However, the majority of people have a hard time restricting calories, especially in Western societies where food is so freely available.
Interestingly, one of their main sources of carbohydrate is sweet potato
"It shows a lot of promise that we have been able to replicate the same kind of gene changes in the part of the brain responsible for memory that we also see when we severely restrict calories."
Low-protein high-carb diets are by no means a new fad.
Senior author Professor David Le Couteur said numerous cultures including the people of Okinawa in Japan and many parts of the Mediterranean have long observed this mix.
Prof Couteur, also of the University of Sydney, said: "The traditional diet of Okinawa is around nine per cent protein, which is similar to our study, with sources including lean fish, soy and plants, with very little beef.
"Interestingly, one of their main sources of carbohydrate is sweet potato."
For the current study, researchers fed the mice complex carbohydrates derived from starch, and casein protein which is found in cheese and milk.
How to live longer diet: Prevent dementia symptoms with high-carb foods
To assess the brain benefits of the diet the researchers focused on the hippocampus, the region of the brain responsible for learning and memory.
Prof Couteur added: "The hippocampus is usually the first part of the brain to deteriorate with neurodegenerative diseases like Alzheimer's.
"However, the low-protein high-carbohydrate diet appeared to promote hippocampus health and biology in the mice, on some measures to an even greater degree than those on the low-calorie diet."
Learning and memory were assessed via a series of tests, with researchers noting modest improvements in male and female mice at both young and old ages.
This research follows a landmark 2015 study. also from the University of Sydney's Charles Perkins Centre, that showed low protein, high carb diets could be just as effective as low calorie diets in promoting a long life in mice through good heart and digestive health.