TUESDAY, April 14, 2020 (HealthDay News) -- Eating a Mediterranean diet that's high in vegetables, whole grains and fish could reduce your risk of mental decline, two studies from the U.S. National Eye Institute (NEI) suggest.
"We do not always pay attention to our diets. We need to explore how nutrition affects the brain and the eye," lead author Dr. Emily Chew said in an NEI news release. She is director of the institute's division of epidemiology and clinical applications.
The researchers analyzed data from the Age-Related Eye Disease Study (AREDS) and the follow-up study, AREDS2. The studies, which included 8,000 people in all, were set up to explore the eye disease age-related macular degeneration.
At the start of both studies, participants' diets were assessed, including their average consumption of specific Mediterranean diet components over the previous year. Besides veggies, whole grains and fish, this type of meal plan is rich in whole fruits, nuts, legumes and olive oil.
A Mediterranean diet also features lower consumption of red meat and alcohol.
AREDS tested participants' mental (cognitive) function at five years, and AREDS2 tested mental function at the start and again two, four and 10 years later.
Those who most closely followed the Mediterranean diet had the lowest risk of mental impairment.
Although the study can't prove a direct cause-and-effect relationship, high levels of fish and vegetable consumption appeared to provide the greatest protection. At 10 years, those in AREDS2 who ate the most fish had the slowest rate of mental decline.
The differences in mental function between participants with the highest and lowest adherence to a Mediterranean diet were relatively small, meaning it's unlikely that individuals would have a difference in daily mental function, the researchers said.
But at a population level, the results clearly show that mental function and brain health depend on diet, according to the authors. The findings were published April 14 in the journal Alzheimer's and Dementia.
The researchers also found that people with the APOE gene -- which puts them at higher risk for Alzheimer's disease -- on average had lower cognitive function scores and greater mental decline than those without the gene.
The benefits of closely following a Mediterranean diet were similar for people with and without the APOE gene. This means the effects of diet on mental function are independent of genetic risk for Alzheimer's disease, according to the researchers.
The U.S. National Institute on Aging has more about declines in memory and thinking.
SOURCE: U.S. National Eye Institute, news release, April 14, 2020