According to a recent analysis of
data from two major eye disease studies, adherence to the Mediterranean diet –
high in vegetables, whole grains, fish, and olive oil – correlates with higher
cognitive function. Dietary factors also seem to play a role in slowing
cognitive decline. Researchers at the National Eye Institute (NEI), part of the
National Institutes of Health, led the analysis of data from the Age-Related
Eye Disease Study (AREDS) and AREDS2. They published their results in the
journal Alzheimer’s and Dementia.
“We do not
always pay attention to our diets. We need to explore how nutrition affects the
brain and the eye” said Emily Chew, M.D., director of the NEI Division of
Epidemiology and Clinical Applications and lead author of the studies.
The researchers
examined the effects of nine components of the Mediterranean diet on cognition.
The diet emphasizes consumption of whole fruits, vegetables, whole grains,
nuts, legumes, fish, and olive oil, as well as reduced consumption of red meat
and alcohol.
AREDS and AREDS2
assessed over years the effect of vitamins on age-related macular degeneration
(AMD), which damages the light-sensitive retina. AREDS included about 4,000
participants with and without AMD, and AREDS2 included about 4,000 participants
with AMD. The researchers assessed AREDS and AREDS2 participants for diet at
the start of the studies. The AREDS study tested participants’ cognitive
function at five years, while AREDS2 tested cognitive function in participants
at baseline and again two, four, and 10 years later. The researchers used
standardized tests based on the Modified Mini-Mental State Examination to
evaluate cognitive function as well as other tests. They assessed diet with a
questionnaire that asked participants their average consumption of each
Mediterranean diet component over the previous year.
Participants
with the greatest adherence to the Mediterranean diet had the lowest risk of
cognitive impairment. High fish and vegetable consumption appeared to have the
greatest protective effect. At 10 years, AREDS2 participants with the highest
fish consumption had the slowest rate of cognitive decline.
The numerical
differences in cognitive function scores between participants with the highest
versus lowest adherence to a Mediterranean diet were relatively small, meaning
that individuals likely won’t see a difference in daily function. But at a
population level, the effects clearly show that cognition and neural health
depend on diet.
The researchers
also found that participants with the ApoE gene, which puts them at high risk
for Alzheimer’s disease, on average had lower cognitive function scores and greater
decline than those without the gene. The benefits of close adherence to a
Mediterranean diet were similar for people with and without the ApoE gene,
meaning that the effects of diet on cognition are independent of genetic risk
for Alzheimer’s disease.
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