Study data that appears in the journal Frontiers in Aging Neuroscience, suggest age-related cognitive decline is less distinct among adults, who increase their intake of lutein and zeaxanthin-rich green and leafy vegetables.
Additionally, the team believe this habit may provide brain benefits in early to middle adulthood before the onset of old age.
"Now there's an additional reason to eat nutrient-rich foods such as green leafy vegetables, eggs and avocados," said Dr Naiman Khan, a professor of kinesiology and community health at the University of Illinois at Urbana-Champaign.
"We know these foods are related to other health benefits, but these data indicate that there may be cognitive benefits as well."
As well as benefits to the brain, lutein and zeaxanthin have been implicated in ocular function and disease as lutein accumulates in the eye as well as the brain.
This observation allows researchers to measure levels of the primary carotenoid in the brain—lutein—without relying on invasive techniques.
Its role in working memory, brain processing, functioning and speed has long intrigued researchers, as lutein is a nutrient that the body cannot make on its own.
Boosting nutrient levels would simply be a matter of increasing their intake via dietary means.
Lutein and zeaxanthin supplementation is another option with previous work on its intervention relatively recent.
The majority of work in this field has targeted specific nutrient supplementation, with evidence suggesting that vitamin D, vitamin B and omega 3 fatty acids acting as neuro-protective agents in aging adults.
Study approach
The study enrolled a sample of 60 healthy adults aged between 25 and 45.
Carotenoid levels were assessed by measuring macular pigment optical density (MPOD), a reliable indicator of lutein levels in the brain.
Event-related brain activity was recorded during the performance of cognitive control tasks and used as an indicator of cognitive function.
Results showed that across all subjects MPOD was related to both age and the specific electrical brain activity during the decision-making process known as the P3 wave.
Although younger adults exhibited larger P3 amplitudes than their older adult counterparts, older subjects with higher MPOD levels displayed P3 measurements similar to their younger adult counterparts in amplitude.
Further analyses showed that age was no longer a significant predictor of P3 amplitude when MPOD was included as a predictor in the model.
Lutein’s protective role
“The neuro-electrical signature of older participants with higher levels of lutein looked much more like their younger counterparts than their peers with less lutein," commented Anne Walk, a postdoctoral scholar and first author of the paper.
"Lutein appears to have some protective role, since the data suggest that those with more lutein were able to engage more cognitive resources to complete the task."
The findings here mirror relationships discovered between MPOD and enhanced neuro-cognition.
Several studies have established a relationship between retinal carotenoids and superior cognitive processing in older and middle aged adults.
In addition, higher MPOD is directly related to a healthy diet. Healthy eating patterns are also related to better cognition across adulthood.
One point of note centres on the choice of subjects. The researchers chose to focus on young to middle-aged adults to see whether there was a notable difference between those with higher and lower lutein levels.
Previous studies have tended to focus on older adults, in which a period of decline has set in.
"We want to understand how diet impacts cognition throughout the lifespan,” added Walk.
“If lutein can protect against decline, we should encourage people to consume lutein-rich foods at a point in their lives when it has maximum benefit."
Source: Frontiers in Aging Neuroscience
Published online ahead of print: doi.org/10.3389/fnagi.2017.00183
“The Role of Retinal Carotenoids and Age on Neuroelectric Indices of Attentional Control among Early to Middle-Aged Adults.”
Authors: Anne Walk, et al