Spanish researchers maintain that following a Mediterranean style diet which is also supplemented with olive oil and mixed nuts may protect older adults from deterioration in cognitive function.
Typically a Mediterranean diet is based around fruit, vegetables, whole grains, legumes, nuts and olive oil- a significantly different diet from many other Western cultures.
The researchers published their study in JAMA, a journal on internal medicine. They based their results on a randomized clinical trial which followed the cognitive change over a period of time among volunteers who were assigned to follow one of three different diets. Volunteers were cognitively healthy, had a high cardiovascular risk and an average age of 67.
The Dietary Guidelines for Americans have already recommended adopting the Mediterranean style diet as a way to improve one’s health and stave off disease. One ought to eat primarily plant-based foods, with every meal based on staples of fruit, vegetables, whole grains, legumes and nuts. One should avoid saturated fats and trans-fats, as these are harbingers of heart disease. Rather one should try and obtain one’s fats from healthier foods such as avocado and extra virgin olive oil, containing mainly monounsaturated fat which improves good cholesterol levels.
Vegetables and healthier fats are also good sources of antioxidants and play an important role in counteracting oxidative stress. Oxidative stress occurs when the body is unable to detoxify itself fully, and the process is believed to play a significant role in cognitive decline.
“Oxidative stress and vascular impairment are believed to partly cause age-related cognitive decline, a strong risk factor for development of dementia,” say the authors. “Epidemiologic studies suggest that a Mediterranean diet, an antioxidant-rich cardioprotective dietary pattern, delays cognitive decline”.
To test this hypothesis, Dr. Emilio Ros of the Institut d’Investigacions Biomediques August Pi Sunyer, Hospital Clinic, Barcelona, and coauthors examined the effects of Mediterranean diets supplemented with olive oil or nuts compared with a low-fat control diet.
A total of 155 participants were randomly assigned to follow a Mediterranean diet supplemented with one liter of extra virgin olive oil per week. Another 147 participants were assigned to follow a Mediterranean diet supplemented with 30 grams per day of mixed nuts (walnuts, hazelnuts and almonds. A further 145 participants were asked to follow a regular low-fat diet.
The researchers measured cognitive change in the participants over time using neuropsychological tests which focus on memory, global cognition and frontal cognition (attention and executive function). The first two groups were compared with the control group of 145 participants following the low-fat diet.
After a median of 4 years of the dietary intervention, follow-up cognitive tests were available in 334 participants. The researchers found there were 37 cases of mild cognitive impairment among the participants: 17 (13.4%) in the group that received extra olive oil, eight (7.1%) in the mixed nuts group and 12 (12.6%) in the control group.
Participants in the control group experienced significant decreases in each measured composite of cognitive function. However the two Mediterranean diet groups in the study experienced different improvements in cognitive function.
“The group with nuts did better compared to the control group in memory tests, memorizing names or words, while the olive oil group did better on tests that require speed of thought, frontal function and executive function,” explained Dr. Ros.
Since not all participants received follow-up cognitive testing, and adherence to all three diets cannot be guaranteed, the research is not entirely conclusive, but the authors still contend that “in an older population, a Mediterranean diet supplemented with olive oil or nuts may counteract age-related cognitive decline. The lack of effective treatments for cognitive decline and dementia points to the need of diet- related preventive strategies to delay the onset and/or minimize the effects of these devastating conditions.”
In the interview with JAMA, Dr. Ros stated that the research team is currently conducting a study into the effects of walnuts on neurodegenerative disease, comparing a walnut diet with a control diet.
Similar studies have been conducted recently in which researchers monitored the diets of older adults for 5 years and tested for cognitive decline. They discovered that those who ate healthily experienced only a small drop in brain power.
In conclusion, diet plays an important part in a person’s retention of cognitive abilities in old age and it is important to maintain healthy eating habits to help maintain those abilities.