The Mediterranean Diet not only has beneficial effects on the cardiovascular health of people who follow it, but it can also allow them to improve their memory and prevent or delay the effects of cognitive decline associated with aging.
However, these beneficial effects do not reach everyone equally, leading to changes in the type of interventions based on dietary recommendations to adapt them to the characteristics of each person. These are the main results of a study published in Clinical Nutrition, led by researchers from the CIBERobn and the Hospital del Mar Medical Research Institute (IMIM-Hospital del Mar). The Bellvitge Biomedical Research Institute (IDIBELL), the Rovira i Virgili University, the University of Valencia and the University of Navarra have also participated in the work.
The study followed a group of 487 volunteers for three years, almost equally divided between men and women and with an average age of 65 years. All were participants in the PREDIMED-PLUS trial (PREVENTION DIeta MEDiterranea Plus), in which 23 research centers of the State participate that analyzes the effect of the traditional Mediterranean Diet with energy restriction, promotion of physical activity and behavioral intervention, in the loss weight loss and prevention of cardiovascular disease. At the start of the study, participants were overweight or obese and had at least three criteria for metabolic syndrome, including hypertension, hyperglycemia, excess waist fat, low HDL cholesterol, and high triglyceride levels. Metabolic syndrome is very common, occurs in about 1 in every four adults in the world, and involves an increased risk of heart disease, stroke, type 2 diabetes, and cognitive decline.
Improve adherence to diet to improve memory
The researchers analyzed, through neuropsychological tests, the cognitive state of the volunteers at the beginning of the study and after one and three years. Their performance in memory and in other cognitive functions was established, including the ability to make decisions, reason, pay attention, plan or ignore certain impulses, as reported by the CIBERobn.
According to previous studies, in a period of three years, people with metabolic syndrome who do not follow any type of intervention, would have presented a decrease of almost 0.40 points in their global cognition and 0.10 points in their memory. On the contrary, with the study's recommendations, they registered improvements of more than 0.60 points in global cognition and of around 0.90 in memory. The units of measurement of cognition are standardized to be able to compare neuropsychological tests that are on different scales.
In all patients, the results indicate a direct relationship between adherence to the Mediterranean Diet and cognitive improvement. Adherence to the hypocaloric Mediterranean Diet is measured with a 17-item questionnaire that explores the consumption of extra virgin olive oil and the number of servings of vegetables and pieces of fruit consumed per day, among others. Scores above 11 points are considered a high adherence to the Mediterranean Diet. Thus, for each point of improvement in adherence to this type of diet, memory improved by 0.13 points. This improvement may be due, according to the researchers, to weight loss and increased physical activity, which is also associated with an improvement in quality of life. In this sense, Rafael de la Torre, principal investigator of the study, has pointed out that this fact “is important, taking into account that cognitive changes may not be perceptible to people, but they may be more relevant if they are combined with improvements in their quality of life".
Not everyone benefits equally from it
"More adherence to the Mediterranean Diet implies a greater improvement in cognition", explained Natàlia Soldevila-Domènech, first signatory of the work. Women, older people, those with a lower educational level and those with type 2 diabetes are the groups that obtain the least benefits from following the Mediterranean Diet. In reference to this fact, the researcher has pointed out that “although we see that women have a lower cognitive improvement than men, these cognitive improvements occurred in all the participants. Everyone benefits from following the Mediterranean Diet, but to a greater or lesser degree”.
At the same time, the volunteers with a lower cognitive performance at the beginning of the study in memory and other cognitive functions, are those who have less adherence to the Mediterranean Diet and those who are less likely to achieve a significant reduction in weight. "We were interested in knowing which volunteers lost weight and which did not, and why some lost and others did not, from the point of view of cognition and their behavior," explained Rafael de la Torre. Specifically, people who at the beginning of the study had better auditory memory, greater planning and decision-making capacity, less reaction time and less impulsivity, were between 20% and 50% more likely to achieve the study objective to lose 8% weight in three years. According to the researchers, this is explained by the fact that the majority of people with these cognitive abilities achieved high adherence to the hypocaloric Mediterranean Diet, which resulted in clinically relevant weight loss.
For these reasons, the authors point out that the results obtained should make it possible to identify the groups with the most difficulties to benefit from these lifestyle interventions, to personalize the measures and thus facilitate them to adopt the proposed healthy life guidelines, thus favoring while preventing cognitive decline.