Older people who followed a Mediterranean diet retained more brain volume over a three-year period than those who did not follow the diet as closely, found a University of Edinburgh study. But contrary to earlier studies, eating more fish and less meat was not related to changes in the brain.
The Mediterranean diet includes large amounts of fruits, vegetables, olive oil, beans and cereal grains such as wheat and rice, moderate amounts of fish, dairy and wine, and limited red meat and poultry.
"As we age, the brain shrinks and we lose brain cells which can affect learning and memory," said study author Dr Michelle Luciano, of the University of Edinburgh in Scotland. "This study adds to the body of evidence that suggests the Mediterranean diet has a positive impact on brain health."
Researchers gathered information on the eating habits of 967 Scottish people around age 70 who did not have dementia. Of those people, 562 had an MRI brain scan around age 73 to measure overall brain volume, grey matter volume and thickness of the cortex, which is the outer layer of the brain. From that group, 401 people then returned for a second MRI at age 76. These measurements were compared to how closely participants followed the Mediterranean diet.
The participants varied in how closely their dietary habits followed the Mediterranean diet principles. People who didn't follow as closely to the Mediterranean diet were more likely to have a higher loss of total brain volume over the three years than people who followed the diet more closely. The difference in diet explained 0.5% of the variation in total brain volume, an effect that was half the size of that due to normal ageing.
The results were the same when researchers adjusted for other factors that could affect brain volume, such as age, education and having diabetes or high blood pressure. There was no relationship between grey matter volume or cortical thickness and the Mediterranean diet. The researchers also found that fish and meat consumption were not related to brain changes, which is contrary to earlier studies.
"It's possible that other components of the Mediterranean diet are responsible for this relationship, or that it's due to all of the components in combination," Luciano said. Luciano noted that earlier studies looked at brain measurements at one point in time, whereas the current study followed people over time.
"In our study, eating habits were measured before brain volume was, which suggests that the diet may be able to provide long-term protection to the brain," said Luciano. "Still, larger studies are needed to confirm these results."
Abstract
Objective: To assess the association between Mediterranean-type diet (MeDi) and change in brain MRI volumetric measures and mean cortical thickness across a 3-year period in older age (73–76 years).
Methods: We focused on 2 longitudinal brain volumes (total and gray matter; n = 401 and 398, respectively) plus a longitudinal measurement of cortical thickness (n = 323), for which the previous cross-sectional evidence of an association with the MeDi was strongest. Adherence to the MeDi was calculated from data gathered from a food frequency questionnaire at age 70, 3 years prior to the baseline imaging data collection.
Results: In regression models adjusting for relevant demographic and physical health indicators, we found that lower adherence to the MeDi was associated with greater 3-year reduction in total brain volume (explaining 0.5% of variance, p < 0.05). This effect was half the size of the largest covariate effect (i.e., age). Cross-sectional associations between MeDi and baseline MRI measures in 562 participants were not significant. Targeted analyses of meat and fish consumption did not replicate previous associations with total brain volume or total gray matter volume.
Conclusions: Lower adherence to the MeDi in an older Scottish cohort is predictive of total brain atrophy over a 3-year interval. Fish and meat consumption does not drive this change, suggesting that other components of the MeDi or, possibly, all of its components in combination are responsible for the association.
Authors
Michelle Luciano, Janie Corley, Simon R Cox, Maria C Valdés Hernández, Leone CA Craig, David Alexander Dickie, Sherif Karama, Geraldine M McNeill, Mark E Bastin, Joanna M Wardlaw, Ian J Deary
[link url="https://www.sciencedaily.com/releases/2017/01/170104174210.htm"]American Academy of Neurology material[/link]
[link url="http://www.neurology.org/content/early/2017/01/04/WNL.0000000000003559"]Neurology abstract[/link]