Associations between nut consumption and changes in cognitive performance were examined.
Is nut consumption beneficial for brain health?
Diet is considered a major modifiable lifestyle factor, and it plays a vital role in regulating other risk factors for certain health conditions.
Peanuts and tree nuts are enriched with nutrients and possess anti-inflammatory and antioxidant properties. Indeed, the various nutrients and active compounds found in nuts can also trigger neuroprotective effects. Nonetheless, there is limited epidemiologic evidence regarding the associations between nut intake and cognitive performance.
While cognitive function and nut consumption have been positively linked in many cross-sectional studies, mixed results have been reported in prospective studies and randomized controlled trials (RCTs). Consequently, the existing evidence regarding the impact of nut intake on cognitive performance remains inconclusive.
About the study
In the present study, associations between nut consumption and changes in cognitive performance over a two-year period were prospectively assessed in a Spanish cohort of older adults at risk of cognitive decline. Inclusion criteria encompassed overweight or obese individuals aged 55 to 75, residing in the community, and presenting with metabolic syndrome at baseline.
A food-frequency questionnaire was completed by participants, evaluating their habitual intake of various food items over the past year. Nut consumption was categorized as follows: less than one serving per week, one to two servings per week, three to six servings per week, and seven or more servings per week. Cognitive performance was evaluated by trained personnel at baseline and after two years.
During personal interviews, eight neuropsychological tests were administered, and cognitive test results were standardized to z-scores for each participant, utilizing baseline data’s mean and standard deviation. Cognitive performance changes were estimated by comparing scores, and composite measures were calculated for a comprehensive evaluation of cognitive function and three cognitive domains: general cognition, executive function, and attention.
The primary outcome focused on changes in composite scores over two years. Sociodemographic, lifestyle, food consumption, medical history, and anthropometric data were collected at baseline. Depressive symptoms were assessed using the Beck Depression Inventory. The impact of nut consumption on changes in cognitive function over two years was explored through multivariable linear regression models.
In this study, there were 6,630 participants included, with an average age of 65, and females constituted 48.4% of the study cohort. The daily average consumption of nuts was 1.7 g for those in the lowest consumption category at baseline and 43.7 g for those in the highest consumption category, with walnuts being the most frequently consumed. Those with the highest consumption exhibited a higher level of education, better adherence to the Mediterranean diet, and greater physical activity compared to those with the lowest intake.
Furthermore, there were fewer individuals who were current smokers or experiencing depressive symptoms in the highest consumption category. Participants with the highest intake also displayed a lower waist circumference and body mass index (BMI) compared to those with the lowest intake.
It was observed a positive association between nut consumption and changes in cognitive performance over a two-year period. In the multivariable models, a daily intake of one serving of nuts was linked to more favorable changes in general cognitive function and the clock drawing test (CDT).
Participants who consumed three to six servings of nuts per week showed more positive cognitive performance trends at the two-year mark than those consuming less than one serving per week. However, this trend was not evident in the highest nut consumption category. These associations between nut intake and cognitive changes over two years remained consistent in sensitivity analyses.
Significant interactions between nut consumption and education level, sex, smoking status, hypertension, hypercholesterolemia, or type 2 diabetes were not observed by our researchers. Nonetheless, our stratified analysis did reveal a connection between more frequent nut consumption and reduced cognitive decline, but only in those who presented depressive symptoms at baseline.
In this current study, higher nut consumption demonstrated associations with more favorable changes in CDT and general cognitive function, suggesting a potential dose-response relationship. It was also noted synergistic interactions between depression and nut intake, suggesting that individuals with depressive symptoms at baseline may derive more significant benefits from nut consumption.
In summary, increased nut consumption may potentially delay cognitive decline over a two-year period in older adults who are overweight or obese and have metabolic syndrome. Nevertheless, additional epidemiological and clinical investigations are required to validate these findings before dietary recommendations can be made for the prevention or delay of dementia and cognitive impairment.