A team of researchers at the Tufts University's Jean Mayer USDA Human Nutrition Research Center on Aging noted that these beneficial effects were largely in part to the fruit's high lutein levels. According to the experts, both the eyes and the brain selectively incorporate the essential carotenoid.
To carry out the study, the research team examined 20 healthy men and women who were randomly assigned to eat one avocado or either one cup of potatoes or chickpeas daily for six months. The avocado provided a daily lutein dose of about 0.5 mg.
The scientists said that daily avocado consumption for six months resulted in a significant increase in lutein levels in plasma and in the macular of the eyes at about 25 percent, compared with only 15 percent in those who ate either potatoes or chickpeas.
Likewise, the scientists also found that only the participants in the avocado group exhibited a marked increase macular pigment density after six months. According to the research team, this effect may serve as a biomarker for lutein levels in the brain.
The health experts also noted that while both groups showed improvements in memory and spatial working memory, only those in the avocado group exhibited significant improvements in sustained attention.
The study also revealed that the marked increase in macular pigment density (MPD) in the avocado group was associated with clinically significant improvements in working memory and problem solving skills.
"This study is an example of how practical dietary choices can be of benefit to healthy aging ... A dietary intervention with avocados was found to improve cognitive function. This improvement could be related to the increase in MPD, a biomarker of lutein contained in brain tissue. The proposed mechanisms by which lutein benefits cognitive function in the elderly may involve its role as an antioxidant or anti-inflammatory agent. However, in this study, no changes in oxidative stress or inflammation biomarkers were detectec in either group. These measures were within a normal range at the start of the study, and therefore an improved antioxidant or anti-inflammatory status would have been difficult to detect," the researchers wrote in the Nutra Ingredients U.S.A. website.
"Other proposed mechanisms by which lutein is embedded in neural tissue include the modulation of functional properties of synaptic membranes, along with certain changes in the physiochemical and structural features of these membranes," the researchers added.
Study: Eating avocadoe may help stave off cognitive aging
Another study, published in Frontiers in Aging Neuroscience, demonstrated the powerful properties of lutein in avocados and other green leafy vegetables against the harmful effects of cognitive aging.
As part of the study, researchers at the University of Illinois at Urbana-Champaign recruited 60 adults aged 25 to 45. The experts then examined the participants' lutein levels and neural activity in the brain during an attention test.
The health experts found that middle-aged participants with higher lutein levels had neural responses that were more similar to the younger volunteers compared with their counterparts with lower lutein levels.
"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... 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," study author Anne Walk told Science Daily online.
The researchers are now conducting tests to demonstrate how increased dietary lutein consumption may raise lutein levels in the eyes, and how nutrient levels may impact cognitive performance.
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