Changing the way we eat can delay ageing in our brain and reduce the risk of dementia.
A low protein, high carb diet may be the key to a longer life, and a new study, published in Cell Reports, has found it may also be the key to better brain health as we age.
Quality carbs, from fruits and vegetables, may improve brain health as we age.Credit:Bonninstudio – Stocksy
For the last century, researchers have known that restricting our energy intake is beneficial for the brain, delaying the onset of neurodegenerative diseases like dementia.
But, it is notoriously difficult for humans to maintain in the long-term.
“If you look at calorie restriction from an evolutionary perspective, animals are meant to function optimally under conditions of mild stress,” explained lead author and PhD candidate Devin Wahl. “For example, if you think of a lion who is hungry, that lion will be alert, awake, and on guard looking for food. That lion’s brain will be optimally functioning.
High red meat consumption has been attributed to adverse health outcomes in humans.
“If you have a lion who is stuffed full all of the time, that lion will be most likely asleep and napping, and the brain is not at optimal functioning. The brain functions best under conditions of mild stress, and develops resilience to the stress of future situations.”
Thankfully, Wahl and his team from the University of Sydney found we don’t need to endure constant stress (or hunger) to experience better brain function.
They compared mice on a kilojoule restricted diet with mice on one of four diets where they could eat as much as they liked.
The diets were based on different macronutrient splits; comprising of either 5, 10, 15 or 19 per cent casein protein, which comes from cheese and milk. The fat intake was fixed at 20 per cent across all diets and remainder of their food came from complex carbs derived from starch.
They found that the low protein, high carb diets (with 5 or 10 per cent protein) were similarly protective to restricting energy by 20 per cent and “significantly improved” cognitive function, including memory and learning even when compared to the other diets.
"It’s not so much the carbs themselves, but rather the ratio of macronutrients. We are starting to identify proper ratios that help brain health during ageing," Wahl explained. "We are finding that low protein, high carb diets recapitulate some of the benefits of calorie restriction with regards to brain ageing.
"Also, the brain needs healthy sources of carbs to function properly. In humans the brain is about 2 per cent of the body weight, but consumes about 20 per cent of all glucose consumed. In other words: carbs are important for optimal brain function – it is just the types of carbs that are important."
Walh believes that eating quality carbs (such as vegetables, sweet potato and fruit) work in the same way as energy restriction by affecting “similar molecular pathways” in the brain, “helping” neurons and reducing inflammation.
Another recent study concluded that a high protein diet may reduce Alzheimer's risk. However Wahl said the authors "focused on Amyloid beta, which is an important contributing factor to Alzheimer’s disease but doesn’t tell the whole story".
The latest study is an "all encompassing" paper examining the multiple factors that contribute to dementia and healthy ageing in general, he added: "Myself and many other scientists in the field would argue that many other factors need to be taken into consideration when looking at the risk for dementia."
Based on his research, he says we should aim to minimise red meat consumption, which Australians eat too much of, and which can drive the ageing process.
“High red meat consumption has been attributed to adverse health outcomes in humans,” Wahl said. “Eat a diet rich in vegetables, whole grains, fruits, and vegetable protein. Fish (salmon and trout) are excellent sources of protein as well."
Understanding how to slow the processes that drive ageing in the brain is significant given that prevention is currently the only cure for dementia, which is the second leading cause of death of Australians.
"Even if one has a genetic risk, we can 'alter the course of our genes' to a certain extent," Wahl said. "And it’s never too late to make positive changes."
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