Could kale and other lutein-rich foods maintain the quality of our cognitive functions?
The health benefits of green foods, such as kale, spinach, and other leafy vegetables, have long been discussed by nutritionists.
The importance of lutein - a nutrient and organic pigment, or carotenoid, found in a range of foods including kale, carrots, and even eggs - has often been singled out by specialists in recent studies. Medical News Today, for instance, have lately reported on lutein's role in reducing inflammation in heart disease.
New research from the University of Illinois at Urbana-Champaign, in collaboration with the University of Georgia in Athens, has unveiled yet another health benefit of lutein: the ability to counteract cognitive aging.
Lead researcher Dr. Naiman A. Khan, of the Department of Nutritional Sciences at the University of Illinois, and his colleagues published their findings in the journal Frontiers in Aging Neuroscience.
Cognitive aging sets in early
The researchers started from the premise that cognitive aging becomes apparent earlier in life than one might expect.
Previous studies had only monitored cognitive aging in elderly adults, but Dr. Khan and his colleagues wanted to take a different approach.
"As people get older, they experience typical decline. However, research has shown that this process can start earlier than expected. You can even start to see some differences in the 30s," says first study author Anne Walk, a postdoctoral researcher also at the University of Illinois.
With this in mind, the researchers recruited 60 adult participants aged between 25 and 45, setting out to investigate whether or not lutein intake can have an impact on cognition.
The researchers explain that lutein is a naturally occurring substance that cannot be synthesized in the human body. This is why it must be absorbed from foods that synthesize it, such as kale and other green leafy vegetables, or else through food supplements.
Once assimilated by the human body, lutein can be detected in brain tissue as well as in the eyes' retinas, which makes the appraisal of lutein levels more convenient, as non-invasive measurements can be taken.
"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," says Walk.
More lutein improves cognitive performance
On this occasion, the researchers gauged lutein levels in the participants' eyes by asking them to respond to flickering light stimuli.
The neural activity in the participants' brains was assessed by electrodes attached to the scalp, as each participant was tasked with an attention-related exercise designed to test their selective attention, attentional inhibition (the ability to ignore irrelevant stimuli), or response inhibition (the ability to suppress inappropriate impulses).
Dr. Khan and colleagues found that the participants who exhibited higher levels of lutein were cognitively more similar to younger individuals than they were to individuals of the same age with lower lutein levels.
"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. 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," explains Walk.
Following this study, the researchers seek to gain a better understanding of how a larger lutein intake might impact the level of the carotenoid accumulated in the retina, and to what extent lutein levels actually influence cognitive capacity.
"In this study we focused on attention, but we also would like to understand the effects of lutein on learning and memory," concludes Dr. Khan.