Carbohydrates have been developing a rather bad reputation as the 21st century has progressed. From low-carb/high-fat diets to more restrictive ketogenic regimes, it seems the growing consensus has simply become "carbs are bad." However, a new study from the University of Sydney suggests a low-protein/high-carb diet can promote healthy aging and improve brain health, perhaps even slowing the onset of dementia.

The research was spawned by the observation that, while we have a large volume of evidence pointing to the many benefits of caloric restriction, it may not be the most sustainable dietary recommendation for many people in the modern world.

"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 Devin Wahl, lead author on the new study. "However, the majority of people have a hard time restricting calories, especially in Western societies where food is so freely available."

The new study, conducted in mice, compared the effects of four different diets that varied in protein and carbohydrate content against a standard 20 percent caloric restriction diet. The results found that a diet low in protein but high in complex carbohydrates resulted in comparable brain aging benefits to caloric restriction.

The research examined behavioral and cognitive differences between each diet using spatial awareness and memory tests, but only modest improvements were observed. The most dramatic effects the researchers found came when they studied the changes in gene expression, particularly in the hippocampus.

"The hippocampus is usually the first part of the brain to deteriorate with neurodegenerative diseases like Alzheimer's," explains senior author on the study, David Le Couteur. "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."

The results follow on from several prior studies from the University of Study revealing low-protein/high carbohydrate diets to be comparable to low-calorie diets in promoting cardiovascular health and extending lifespan. The correlation between healthy brain aging and a small volume of carbohydrate consumption is also one echoed by other research, particularly a study from 2008 finding that low-carb diets can impair cognition.

The research also compellingly mirrors a huge amount of study affirming the health benefits of diets rich in complex carbohydrates and low in protein, such as those seen in the Mediterranean and some parts of Japan.

"The traditional diet of Okinawa is around nine percent protein, which is similar to our study, with sources including lean fish, soy and plants, with very little beef," says Le Couteur. "Interestingly, one of their main sources of carbohydrate is sweet potato."

So while this study isn't suggesting all carbohydrates are good and we should go crazy on the bread and pasta, it is a reminder that healthy eating isn't as simple as just saying fat is good and carbs are bad. Instead, a well-rounded and healthy diet is a little more complicated, much to the chagrin of those looking for a straightforward and easy diet plan.

The new research was published in the journal Cell Reports.