Brain power in older people at risk for vascular dementia seems to improve more from a Mediterranean diet with added mixed nuts or extra virgin olive oil than from a low-fat diet that is typically followed to prevent heart attack and stroke, according to the results of a Spanish trial.
People on a Mediterranean diet consume virgin olive oil as their main source of fat, and eat lots of fruits, nuts, vegetables and pulses foods. They also consume a moderate to high amount of fish and seafood, a moderate amount of red wine, but low quantities of dairy products and red meat.
The researchers, from the University of Navarra, report the trial results in a paper that was published online this month in the Journal of Neurology Neurosurgery and Psychiatry, which is published by the BMJ.
The participants of the trial, 522 men and women aged between 55 and 80, were taking part in the PREDIMED trial to investigate how best to ward off heart disease.
The trial team has already reported, earlier this year, that a Mediterranean diet supplemented with extra-virgin olive oil or nuts reduced the incidence of major cardiovascular events (heart attack, stroke, cardiovascular death) among people with high cardiovascular risk.
When they enrolled on the study, none of the participants had cardiovascular disease but were considered to be at high vascular risk because of other pre-existing diseases or conditions.
The researchers counted having type 2 diabetes, or any three of the following conditions, as being at high risk for vascular disease: being a smoker, having high blood pressure, having an unhealthy blood fat profile, being overweight, or having a family history of developing cardiovascular disease early in life.
The team randomly allocated the participants at the start of the study to one of three groups. In one group, the participants followed a Mediterranean diet with added olive oil, in a second group, they followed a Mediterranean diet with added mixed nuts, and in the third group (the controls) they were given advice on how to follow a low fat diet that is usually recommended for reducing risk of heart attack and stroke.
The team followed the participants for an average of 6.5 years, during which they visited the family doctor for regular check ups, and every three months, had checks to see if they were following the diet plan they had been allocated.
All participants underwent assessments of memory, attention, language, orientation, spatial awareness, abstract thinking, and other brain functions. For these they completed two tests, a Mini-Mental State Examination (MMSE) and a Clock Drawing Test (CDT).
The results showed that at the end of the trial 60 participants had developed mild cognitive impairment (MCI, a condition that often leads to dementia). 18 of the 60 were on the Mediterranean diet with added olive oil, 19 were on the Mediterranean diet with added mixed nuts, and 23 were in the low fat diet group (the controls).
Another 35 of the participants developed dementia over the follow up. These included 12 on the Mediterranean diet with added olive oil, 6 on the Mediterranean diet with added mixed nuts, and 17 in the control group on the low fat diet.
Brain function test score averages were significantly higher for the two Mediterranean diet groups than for the control group on the low fat diet.
The results remained true even after the researchers ruled out effects from other factors that might influence them, such as age, physical activity, education, vascular risks, depression, calorie consumption, BMI, alcohol intake, family history of MCI or dementia, or the presence of the Alzheimer’s disease marker ApoE.
“An intervention with MedDiets enhanced with either EVOO [extra virgin olive oil] or nuts appears to improve cognition compared with a low-fat diet.”
The team accepts that a limitation of the study is the rather small sample size, and since all participants were classed as having a high risk of developing vascular disease, you can’t say these findings represent the population at large.
But, the researchers point out no other trial examining the effect of following a Mediterranean diet on brain power has lasted this long. So these findings, they argue, add valuable knowledge to the growing pile of evidence that suggests a good diet protects brain power as we age.
Written by Catharine Paddock PhD