BRAIN FOOD
Your food choices could shrink your grey matter, warns a new study. Its author tells Peta Bee why.
We all know that a bowl of fresh fruit is better for us than an ultraprocessed snack. But when it comes to our brain health, scientists have found that there is no single wonder food or trendy nutrition regimen that beats a balanced diet. For a new study in Nature Mental Health Journal, researchers examined the food preferences of more than 180,000 UK adults with an average age of
70 to find out how those choices affected their cognitive function and mental wellbeing.
The team asked those taking part to rate more than 150 foods and drinks. Categorising each item into one of 10 groups – dairy, beverages, alcohol, vege, starches, snacks, meat, fish, fruit and flavourings – they then added to the mix findings from a range of physical tests, including MRI brain imaging scans, tests of cognitive function and blood metabolite biomarkers, genetics and mental health evaluations. This data was put through AI algorithms to come up with what the investigators believe are the most comprehensive insights to date on the relationship between diet and brain health.
Dr Wei Cheng, a principal investigator at the Institute of Science and Technology for BrainInspired Intelligence at Fudan University, and one of the paper’s authors, says the study is unique because “it is the first time that a large-scale exploration of food preferences and their significant associations with brain health using neuroimaging MRI techniques has been carried out”.
The participants were categorised into one of four distinct eating groups: 18% of people fell into a “starch-free or low-starch” reduced-carb diet, which either excluded or reduced starchy carbs including potatoes, rice, bread and pasta but did include non-starchy carbs (most other vegetables and fruit); 19% adopted a high-protein and lowfibre approach, prioritising protein (meat, fish and dairy) but with minimal fruit and vegetables; 6% were vegetarian or plant-based eaters; and the remaining 57% adopted a “balanced” diet that didn’t exclude any notable food groups (this included pescatarians, as long as they didn’t further restrict their diets by not eating foodstuffs such as wholegrains).
As much as we might think that adopting a plantbased or low-carb diet is the best way to improve health, Cheng’s results found otherwise.
“People who ate a more balanced diet had better ‘fluid intelligence’ [their ability to solve new problems] and better processing speed, memory and executive functions [the set of mental skills that includes flexible thinking and self-control] than all the other diets,” Cheng says. “The balanced diet also corresponded to better brain health with betterstructured neurons or brain cells, which are key markers of good brain health.”
Balanced eaters also had better “brain morphology”, he says, exhibiting higher amounts of grey matter, the outermost layer of the brain responsible for controlling movement, memory and emotions. “This was especially strong when compared with those who followed high-protein and low-fibre diets,” Cheng says. “Individuals on a mixed diet had particular high amounts of grey matter volume in certain brain regions such as the postcentral gyrus, parahippocampal gyrus and inferior parietal gyrus, suggesting better brain health.”
Where vegetarian diets probably fall down is in their lower protein content. Cheng says their findings support previous research that shows restrictive plant-based diets are associated with worse mental health. “People who had strong preferences for eating mostly vegetables and fruits and less protein exhibited a relatively worse mental health status. That included more anxiety and depression symptoms, mental distress and a relatively lower wellbeing score.”
Low-starch, high-protein diets tend to lack fibre, which research at the APC Microbiome Ireland Centre at University of Cork has found to help boost microbes in the gut. These play a key role in regulating brain functions, particularly emotional processing and behaviour. All of the balanced dieters ate some starchy foods such as brown rice, wholegrain breakfast cereal and wholemeal bread, which contributed to their “better mental health status”, Cheng says.
Scientists already know that some foods are better – or worse – for cognitive health than others. Although ultra-processed foods (UPF) weren’t a big focus of the new study, several previous ones have highlighted how a high consumption of UPFs – which include refined cereal, crisps and ready meals – adversely affect brain health whereas nuts, vegetables, wholegrains, seeds and oily fish can protect it.
Neurologists who tracked nearly 11,000 adults for a decade for one paper showed that the more UPFs people ate, the worse their cognitive function. Diets previously shown to be healthy for the brain include the Mind (Mediterranean intervention for neurodegenerative delay) diet, which contains vegetables – particularly the leafy variety such as spinach and kale – some fish and poultry, nuts, pulses and olive oil. Also beneficial is the Mediterranean diet, which prioritises fruit, vege, fruit, oil and three or more servings of oily fish a week.
Last year scientists reported that people who followed either had lower levels of harmful peptides called beta-amyloid and tau protein, both markers for Alzheimer’s, in their brains. Japanese diets rich in rice, fish, pickles and fruits have also been shown to protect against brain shrinkage.
Cheng and his team say a pick-and-mix approach with elements of these diets and other foods now known to be healthy for the brain is the best way to protect against cognitive decline. .
Here’s what you should be sure to include: