According to a recent analysis of data from two major eye disease studies, a Mediterranean diet — high in vegetables, whole grains, fish and olive oil — is associated with superior cognitive function. Dietary factors also appear to play a role in reducing 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 findings in the journal Today Alzheimer’s and Dementia.
“We don’t always pay attention to what we eat. We need to explore how nutrition affects the brain and eyes,” said Emily Chew, MD, director of the NEI Division of Epidemiology and Clinical Applications and lead author of the study.
Researchers tested the effects of nine components of the Mediterranean diet on cognition. The diet emphasizes whole fruits, vegetables, whole grains, nuts, legumes, fish and olive oil, as well as red meat and less alcohol.
AREDS and AREDS2 evaluated the vitamin’s effect on age-related macular degeneration (AMD), which damages the light-sensitive retina, over the years. AREDS included approximately 4,000 participants with and without AMD, and AREDS2 included approximately 4,000 participants with AMD. Researchers assessed AREDS and AREDS2 participants for diet at the start of the study. The AREDS study tested participants’ cognitive function at five years, while the AREDS2 tested participants’ cognitive function at baseline and again after two, four and 10 years. Researchers have used standardized tests to assess cognitive function as well as other tests based on the modified Mini-Mental State Examination. They assessed the diet with a questionnaire that asked participants their average consumption of each Mediterranean food item over the previous year.
Participants with the highest adherence to the Mediterranean diet had the lowest risk of cognitive impairment. High fish and vegetable consumption appears to have the greatest protective effect. At 10 years, AREDS2 participants with the highest rates of fish consumption had the lowest rates of cognitive decline.
Numerical differences in cognitive function scores between participants with highest versus lowest adherence to a Mediterranean diet were relatively small, meaning that individuals would likely not see differences in daily function. But at the 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 higher risk for Alzheimer’s disease, had lower cognitive function scores on average and more decline than those without the gene. The benefits of closely adhering to a Mediterranean diet were similar for people with and without the ApoE gene, meaning the diet’s effects on cognition are independent of genetic risk for Alzheimer’s disease.