The effect of nut exposure on cognitive performance

By Bhavana KunkalikarReviewed by Danielle Ellis, B.Sc.Feb 20 2023

In a recent study published in Nutrients, researchers assessed the effects of consuming nuts on cognition.

Background

Cognitive health is influenced by changeable risk factors, like lifestyle decisions, including dietary consumption, and has important implications for the global quality of life, mortality, and morbidity. Nuts are nutrient-dense and contain a variety of potentially neuroprotective factors, such as monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs), B-vitamins, fiber, highly bioactive polyphenols, and non-sodium minerals.

Increasing nut consumption is associated with a lower risk of cardiovascular diseases (CVD) and a lower load of cardiovascular risk factors common to those in neurodegenerative illnesses, leading to the hypothesis that nuts are helpful for brain health.

Prenatal cognitive development and nut consumption

It is believed that the period of in utero proliferation during gestation is particularly crucial for neurodevelopment, as the brain experiences a number of processes that are unique in their intensity and complexity. During this stage of brain development, crucial nutrients, like omega-3 fatty acid alpha-linolenic acids (ALAs), which are found in nuts, especially walnuts, may impact the epigenetic control of neural mechanisms, neuron formation, and migration, along with axon and dendritic proliferation, myelination, and synaptogenesis.

A child's neuropsychological development, academic performance, and future career achievement may be enhanced by in utero nutrition that facilitates neurodevelopment. In child neurodevelopment, however, the potential protective impacts of nut consumption on cognitive well-being need further research. There is limited data from clinical and epidemiological studies examining nut consumption on brain functioning during pregnancy and childhood or adolescence. In general, the authors discovered that higher consumption of nuts by mothers during early pregnancy was related to increased cognitive development in their offspring at ages 1.5, five, and eight years compared to non-consumers.

Intake of nuts and cognitive health among young adults

Nutrition, in the form of certain fatty acids, is crucial for brain development. Important fatty acids include long-chain PUFAs (LC-PUFAs), which are not produced by the human body and, therefore, must be consumed via a diet including seeds, nuts, and oily fish. Throughout the several phases of life, LCPUFAs play a role in the structure and function of the central nervous system. It has been demonstrated that the LC-PUFA docosahexaenoic acid (DHA) modulates neurotransmission systems, including the dopaminergic, serotonergic, acetylcholinergic, and norepinephrinergic systems.

The omega-3 PUFA ALA, found in walnuts, is associated with the cognitive functioning of older persons. Nonetheless, it has not been investigated sufficiently among children. A recent cross-sectional research of 332 healthy adolescents found that ALA proportions of red blood cells were inversely related to impulsivity. The results of this study provided evidence that nuts, especially walnuts, may have a positive effect on cognition.

Epidemiology research investigating the association between nut intake and cognitive function

A total of 15 papers comprising seven cross-sectional and eight prospective cohort studies were discovered in assessing epidemiological literature examining the relationship between nut consumption and cognitive activity. Among the 15 studies, 13 demonstrated a positive correlation between nut intake and cognitive function; however, favorable relationships were not detected for all cognitive tests in each study.

Several cross-sectional studies have demonstrated positive associations between nut intake and cognitive functioning. A cross-sectional investigation studying the connection of nut consumption with cognitive performance was embedded in the Prevención con Dieta Mediterránea (PREDIMED) project.

The cross-sectional study examined the relationship between the consumption of different diets and cognitive function. Only coffee, olive oil, wine, and walnuts, but not total nuts, were associated with improved cognitive function, irrespective of recognized risk factors for cognitive decline and other dietary consumption. Notably, total urinary polyphenol excretion, an objective indicator of consumption of polyphenol-rich foods, displayed a direct correlation with working memory function.

In terms of specific types of nuts, walnuts were the most examined and were reported to be connected with improved cognitive performance compared to low or non-consumers. However, most studies analyzed the total nut intake as a whole and either did not or could not differentiate the analyses according to the different varieties of nuts.

Cognitive performance results of randomized controlled studies of nuts

Two well-powered and long-term PREDIMED sub-studies that examined the impact of nut-supplemented MedDiets on cognitive performance noted a beneficial influence in older persons at high CVD risk. However, improved cognitive functioning may not be entirely due to nut consumption since other contents of the MedDiet were altered in these studies. Despite this, the MedDiet supplemented with nuts decreased the relative risk of stroke by approximately 50% in the PREDIMED study, providing more evidence for the neuroprotective impact of nuts.

Conclusion

Overall, the study findings showed that although the clinical, epidemiological, and mechanistic evidence is weak and ambiguous, the results suggest that nuts may play a role in the maintenance of cognitive functioning and mitigation of cognitive decline among individuals of all ages, especially older adults. Given the possible cognitive health benefits of nuts, their use as part of a healthy diet may provide a public health strategy for preventing cognitive decline in most people.