A Mediterranean diet with added extra virgin olive oil or mixed nuts seems to improve the brain power of older people better than advising them to follow a low-fat diet, indicates a new study in the Journal of Neurology Neurosurgery and Psychiatry.
Researchers from Spain base their findings on 522 men and women, aged 55 to 80, without cardiovascular disease but at high vascular risk because of underlying disease/conditions. These included either type 2 diabetes or three of the following: high blood pressure, unfavourable blood fats, overweight, a family history of early cardiovascular disease, and being a smoker.
Participants were randomly allocated to a Mediterranean diet with added olive oil or mixed nuts or a control group receiving advice to follow the low-fat diet typically recommended to prevent heart attack and stroke.
A Mediterranean diet is characterized by the use of virgin olive oil as the main source of fat, high consumption of fruits, nuts, vegetables and pulses, moderate to high consumption of fish and seafood, low consumption of dairy products and red meat, and moderate intake of red wine.
Participants had regular check-ups with their family doctor and quarterly checks on their compliance with their prescribed diet.
After an average of 6.5 years, they were tested for signs of cognitive decline using a Mini Mental State Exam and a clock drawing test, which assess higher brain functions, including orientation, memory, language, visuospatial and visuoconstrution abilities and executive functions such as working memory, attention span, and abstract thinking.
At the end of the study period, 60 participants had developed mild cognitive impairment: 18 on the olive oil supplemented Mediterranean diet; 19 on the diet with added mixed nuts; and 23 on the control group.
A further 35 people developed dementia: 12 on the added olive oil diet; six on the added nut diet; and 17 on the low fat diet.
The average scores on both tests were significantly higher for those following either of the Mediterranean diets compared with those on the low fat diet.
These findings held true irrespective of other risk factors for cognitive impairment: family history of cognitive impairment or dementia, the presence of ApoE protein (associated with Alzheimer's disease), education level, exercise level, vascular risk factors, energy intake and depression.
The authors acknowledge that because the study involved a group at high vascular risk, it the findings may not be applicable to the general population.
However, the findings add to the increasing body of evidence suggesting that a high quality dietary pattern seems to protect cognitive function in the aging brain.
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