We are told to avoid carbohydrates for a svelte figure.
But low-protein, high-carb diets may be the key to living longer and protecting against dementia, suggests a new study.
Researchers at the University of Sydney found that mice fed such a diet showed improvements in overall well-being and brain health, plus learning and memory, reports the Daily Mail.
Now, they study's authors believe that similar result could be seen in humans.
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.
Devin Wahl, a PhD candidate who led the analysis, 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.
"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.
"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 Japan's Okinawa and many parts of the Mediterranean have long observed this mix.
"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," he said.
"Interestingly, one of their main sources of carbohydrate is sweet potato."
For the study, researchers fed the mice complex carbohydrates derived from starch, and casein protein which is found in cheese and milk.
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.
Dr James Pickett, Head of Research at Alzheimer's Society, commented: "This diet appears to promote some aspects of healthy brain ageing in mice, but we don't know if it would have the same effects in people or whether it could impact the risk of developing dementia.
"Although this study looked at brain ageing generally and not dementia specifically, mounting evidence highlights the relationship between lifestyle factors such as diet and dementia risk, so Alzheimer's Society is funding a long-term study of 700 people at risk of dementia to better understand these links.
"With nothing yet to slow or stop dementia, prevention is key - and we know simple changes like eating healthy and exercising regularly can reduce our risk, so why not swap box sets and biscuits for a brisk walk."
Almost 70, 000 Kiwis are living with dementia today, with numbers set to rise to 170, 000 by 2015.
Dementia impacts around 30 per cent more women than men.
The disease is thought to be largely caused by genetics but smoking, obesity and lack of exercise increase the risk.