Eating a diet rich in fruits and vegetables can promote healthy brain aging.
It found links between blood markers of certain nutrients in the Mediterranean diet and mental performance and brain connectivity in older adults.
Previous research suggested that older adults who most closely follow a Mediterranean diet have better brain function.
In the new study, scientists at the University of Illinois at Urbana-Champaign applied a more rigorous approach than most investigations of diet and brain health.
As well as testing cognitive function, they used MRI scans to evaluate efficiency in certain brain networks. In addition, instead of using diet surveys — which rely on people's recall — they measured blood levels of nutrients.
The journal NeuroImage has published a report on the study.
"The basic question we were asking," says senior study author Aron K. Barbey, a psychology professor in the University's Beckman Institute for Advanced Science and Technology, "was whether diet and nutrition are associated with healthy brain aging."
"And," he adds, "instead of inferring brain health from a cognitive test, we directly examined the brain using high-resolution brain imaging."
Mediterranean diet blood markers
The Mediterranean diet is rich in fruits, nuts, vegetables, legumes, whole grains, seafood, and olive oil, and it limits red meat and sweets.
Much research has ascribed lower rates of chronic illnesses and longer lifespan in Mediterranean countries to the dietary and lifestyle traditions of their people.
In 2013, UNESCO added the Mediterranean diet to their Representative List of the Intangible Cultural Heritage of Humanity.
In the United States, the Dietary Guidelines 2015–2020 give the Mediterranean-Style Eating Pattern as an example of a healthful diet.
For the recent study, Prof. Barbey and team measured blood markers of 32 key Mediterranean diet nutrients in 116 healthy adults aged 65–75 years.
These individuals also completed a batch of cognitive function tests and underwent a type of MRI scan from which the team could measure "brain network efficiency within seven intrinsic connectivity networks."
The team found links between five "nutrient biomarker patterns" and better results on tests of memory, general intelligence, and executive function.
'Enhanced brain network efficiency'
The scientists also found links between another three nutrient biomarker patterns and "enhanced functional brain network efficiency." The nutrients in these patterns included omega-3 and omega-6 fatty acids and carotene.
Measuring brain network efficiency sheds light on information communication. Prof. Barbey and his team examined "local efficiency" and "global efficiency."
Local efficiency, explains Prof. Barbey, is a measure of information sharing in a "confined set of brain regions." Global efficiency, meanwhile, "reflects how many steps are required to transfer information from any one region to any other region in the network."
The more efficient a person's brain network configuration, the easier it should be, "on average, to access relevant information and the task should take [them] less time," he adds.
Sources of nutrients in biomarker patterns
Walnuts, fish, and Brussels sprouts are some of the rich sources of omega-3 fatty acids. Omega-6 is abundant in flaxseed, pistachios, pine nuts, and pumpkin seeds.
Lycopene, a red pigment that gives tomatoes their color, is present in a few other vegetables and fruits.
Eggs, fortified cereals, and certain green vegetables are typical sources of riboflavin, or vitamin B-2.
Sweet potatoes and carrots get their orange color from carotenoids, while folate is a B vitamin present in many types of food, including beans, peas, and nuts.
Vitamin D abounds in fatty fish such as mackerel, tuna, and salmon, and in certain fortified foods.
When they repeated the analysis with 40 of the study participants about 2 years later, the scientists found largely similar patterns as those from the original group. This suggests that the nutrient biomarker patterns remain stable over time.
However, they urge for further studies to confirm the results.
"Our study suggests that diet and nutrition moderate the association between network efficiency and cognitive performance."
Prof. Aron K. Barbey