Regular nut consumption linked to sharper minds

A recent study published in The American Journal of Clinical Nutrition investigated associations between nut consumption and changes in cognitive performance.

study: Higher versus lower nut consumption and changes in cognitive performance over two years in a population at risk of cognitive decline: a cohort study. Image credit: CreatoraLab / Shutterstock.com

Are nuts good for brain health?

Diet is considered a major modifiable lifestyle factor and plays a vital role in regulating other risk factors for certain health conditions.

Peanuts and nuts are nutrient-dense and have anti-inflammatory and antioxidant properties. In fact, the various nutrients and active compounds present in nuts can also induce neuroprotective effects. However, there is limited epidemiological evidence for associations between nut intake and cognitive outcomes.

While many cross-sectional studies support that cognitive function and nut consumption are positively associated, prospective studies and randomized controlled trials (RCTs) have reported mixed results. Thus, existing evidence on the impact of nut intake on cognitive outcomes remains inconclusive.

About the research

In the current study, researchers prospectively assessed associations between nut consumption and two-year changes in cognitive outcomes in a Spanish cohort of older adults at risk of cognitive decline. Obese or overweight community-dwelling individuals between the ages of 55 and 75 years with metabolic syndrome at baseline were eligible for inclusion.

Participants completed a food frequency questionnaire that assessed usual intake of various food items over the past year. Nut consumption was stratified as less than one serving each week, one to two servings each week, three to six servings each week, and seven or more servings each week. Trained personnel assessed cognitive performance at baseline and after two years.

Eight neuropsychological tests were administered during personal interviews. Cognitive tests were standardized to a z-score for each participant using the mean and standard deviation of the baseline data.

The difference between scores was assessed to examine changes in cognitive outcomes. Composite measures were calculated for a global assessment of cognitive function and three cognitive domains, including general cognition, executive function, and attention.

The primary outcome was two-year changes in composite scores. Data on sociodemographics, lifestyle, food consumption, medical history, and anthropometry were obtained at baseline.

Depressive symptoms were assessed using the Beck Depression Inventory. Associations of nut consumption with two-year changes in cognitive function were examined using multivariate linear regression models.

Survey results

The study included 6,630 participants with an average age of 65, with women representing 48.4% of the study cohort. Mean daily nut consumption was 1.7 g and 43.7 g in the lowest and highest consumption categories at baseline, respectively, with walnuts being the most consumed. Individuals with the highest consumption had higher education, better adherence to the Mediterranean diet, and higher physical activity than those with the lowest intake.

In addition, there were fewer current smokers and depressed individuals in the highest consumption category. Participants with the highest intake also had lower waist circumference and body mass index (BMI) than those with the lowest intake.

A positive association was observed between nut consumption and changes in cognitive outcomes over two years. In multivariate models, one serving of nuts per day was associated with more favorable changes in general cognitive function and the Clock Drawing Test (CDT).

Participants consuming three to six servings of nuts each week had a better evolution of cognitive outcomes at two years than those consuming less than one serving each week. This finding was not observed for the highest nut consumption category. Associations between nut intake and two-year cognitive changes were similar in sensitivity analyses.

The researchers did not observe significant interactions of nut intake with education level, sex, smoking status, hypertension, hypercholesterolemia, or type 2 diabetes. Stratified analysis revealed an association between more frequent nut consumption and less cognitive decline only in those with depressive symptoms at baseline.

Conclusions

In the present study, higher nut consumption was associated with more favorable changes in CDT and general cognitive function, thus indicating a potential dose–response relationship. Synergistic interactions between depression and nut intake were also observed, suggesting that people with depressive symptoms at baseline are likely to benefit more from nut consumption.

Taken together, higher nut consumption may delay cognitive decline by two years in overweight or obese older adults with metabolic syndrome. However, further epidemiological and clinical studies are needed to confirm these findings before dietary recommendations can be made to delay or prevent dementia and cognitive impairment.