Despite
that bias, they really are
University of Illinois
at Urbana-Champaign, News Bureau
A diet including daily
avocado consumption improves the ability to focus attention in adults whose
measurements of height and weight are categorized as overweight or obese, a new
randomized control trial found.
Researchers at the
University of Illinois at Urbana-Champaign conducted the 12-week study,
published in the International Journal of Psychophysiology.
"Previous work
has shown that individuals with overweight and obesity are at higher risk for
cognitive decline and dementia in older age," said kinesiology and
community health professor Naiman Khan, who led the study. "We are
interested in whether dietary approaches may have benefits for cognitive
health, especially in midlife."
The Hass Avocado Board
and the U.S. Department of Agriculture's National Institute of Food and
Agriculture supported this work.
Avocados are high in lutein, a dietary component associated with cognitive benefits. Though avocado consumption's benefits have been studied in older adults and children, no randomized controlled trials had studied its cognitive effects on adults with overweight or obesity, despite 70% of the American adult population falling into that category, said graduate student Caitlyn Edwards, the first author of the study.
In the new study, the
researchers provided 12 weeks of daily meals to 84 adults with overweight or
obesity. The meals were identical in calories and macronutrients, but one
group's meals included a fresh avocado every day, while the control group had
no avocado in their meals.
At the beginning and
end of the study, the participants completed three cognitive tests to measure
attention and inhibition. In addition, the researchers measured lutein levels
in the participants' serum and in their retinas, which is associated with the
lutein concentration in the brain.
They found that the
participants whose diets included avocados improved their performance on one of
the cognitive tests, called the Flanker task, which measures attentional
inhibition -- the ability to maintain focus on the task at hand even in the
face of distraction. However, there was no difference in the other two
cognitive tests.
"It could be that
nutrients in avocados have a specific action in the brain that supports the
ability to do this task in particular, or they could be more beneficial for
certain cognitive abilities over others," Khan said.
"It's also possible that with a longer study or different tests, we could see other effects. Other studies have found broader effects in other populations, so it is interesting to see a more specific benefit for this population."
"It's also possible that with a longer study or different tests, we could see other effects. Other studies have found broader effects in other populations, so it is interesting to see a more specific benefit for this population."
Another unexpected
finding was that, while the participants who ate avocados had higher levels of
lutein at the end of the study, the changes in lutein levels were not
correlated with their cognitive changes.
"Avocados also
are high in fiber and monounsaturated fats. It is possible that these other
nutrients may have played a role in the cognitive effects we saw, but we
focused on the lutein in our analyses," Edwards said. "Future
analyses may focus on other nutrients found in avocados, or avocado
consumption's impact on other measures such as weight status, inflammation and
potential changes in the microbiome."
Although this study
focused on avocados, other dietary sources of lutein, fiber and unsaturated
fats -- such as green leafy vegetables or eggs -- also have potential cognitive
and health benefits. The researchers say their study shows that small dietary
changes, such as eating avocados, can have measurable impacts on cognitive
performance, even when other health behaviors remain the same.
"Our mission is
to give people options. There are multiple ways people can eat to optimize
brain health," Khan said. "What we're learning is that avocados may
be one of those fruits that may be neuroprotective in certain ways. This work
provides some evidence behind one option people have from a plethora of
healthful foods that we can consume."