Lead author and Ph.D. candidate Devin Wahl says, "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."
For the first time, research shows that unrestricted low-protein, high carbohydrate diets have similar protective benefits for the brain as calorie restriction, which is known for its longevity benefits, but it is not sustainable in humans. "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," says Wahl.
"However, the majority of people have a hard time restricting calories, especially in Western societies where food is so freely available. 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."
According to Senior author Professor David Le Couteur, numerous cultures including those who live long lives in Okinawa in Japan, and many parts of the Mediterranean have long observed this mix. In Okinawa, around 9% of protein comes from lean fish, soy and plants, with very little beef. One of their main sources of carbohydrates is sweet potato.
In the current study, researchers fed the mice complex carbohydrates derived from starch and casein protein, which is found in cheese and milk. This assessed the brain benefits of the diet. The researchers focused on the hippocampus - this region of the brain is responsible for learning and memory. Professor Couteur, Professor of Geriatric Medicine at the University of Sydney says "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."
This latest research follows a 2015 study from the University of Sydney's Charles Perkins Center. The study showed that a low protein, high carbohydrate diet could be just as effective as a low-calorie diet in promoting a long life in mice through good heart and digestive health.