Teenage brain boost: Study finds regular walnut consumption could improve cognitive development

19 Apr 2023 --- Adolescents increased their attention in school and improved their fluid intelligence by consuming 30 grams of walnuts daily for at least 100 days over six months, researchers have revealed Study participants with attention deficit hyperactivity disorder (ADHD) also significantly improved their behavior, paying more attention to their teacher and being less hyperactive.

Fluid intelligence is reasoning ability and the ability to generate, transform and manipulate different types of novel information in time.

However, the authors warn the proposed intervention is “unlikely to work in real life” as it requires a strong commitment. Only one-third of the study’s participants consistently consumed walnuts throughout the program. 

“Adolescence is a period of great brain development and complex behaviors that requires a significant amount of energy and nutrients,” explains lead author Ariadna Pinar from the Institut d’Investigació Sanitària Pere Virgili in Spain.

“If boys and girls would heed these recommendations and actually eat a handful of walnuts a day, or at least three times a week, they would notice many substantial improvements in cognitive abilities and it would help them face the challenges of adolescence and entering adulthood.” 

Walnuts are rich in alpha-linolenic fatty acid (ALA), a type of omega 3 that plays an important role in brain development. The authors note that additional clinical and epidemiological research on the effects of walnuts and ALA on neurodevelopment in adolescents is key. 

The study found cognitive health benefits for adolescents that consumed 30 grams of walnuts daily for at least 100 days over six months.The study included 771 healthy high school students participating in the Walnuts Smart Snack Dietary Intervention trial. They were aged 11 to 16, from twelve different schools in Barcelona, Spain. 

Sticking with it 
The study’s first analyses, published in eClinicalMedicine, only found significant changes in adolescent neurodevelopment after accounting for non-adherence to daily walnut intake recommendations. 

“Overall, no significant differences were found in the intervention group concerning the control group, but if the adherence factor is considered, then positive results are observed,” explains co-author Jordi Julvez, principal investigator and coordinator of the Clinical and Epidemiological Neuroscience Group in Tarragona, Spain.  

“Participants who most closely followed the guidelines - in terms of the recommended dose of walnuts and the number of days of consumption - did show improvements in the neuropsychological functions evaluated.”

Although fluid intelligence increased with regular walnut consumption, Julvez adds this “is less influenced by learning. It is inherent to a person’s biological status. We assessed it with increasingly complex tests, such as having adolescents figure out what pattern a row of letters followed.”

Study set-up 
The participants were randomly divided into a control group – which received no intervention – and an intervention group. This second group received bags containing 30 grams of raw Californian walnut kernels to include in their daily diet over six months. 

On average, adolescents in the intervention group consumed walnuts for 70 days. Only 34% of participants consumed walnuts daily for over 100 days during the 180 days study. 

After the study, the research team found that red blood cell ALA status was slightly higher in the walnut group. 

Families in the intervention group received instructions on encouraging their adolescents to eat their daily walnuts and monitor their teens’ adherence to walnut consumption in a weekly report. 

Only 34% of the study’s participants consistently consumed walnuts throughout the program.Future studies should consider a more extended intervention period and brain imaging, which could help detect small brain activity and expression of functional brain works. 

Moreover, more research is needed to determine to what extent the study’s outcomes result from ALA alone or due to synergies with other antioxidant and anti-inflammatory components of walnuts. 

Walnuts’ health benefits 
Julvez explains that neurons well nourished with the type of fatty acids in walnuts can grow and form new, stronger synapses.

“Adolescence is a time of great biological changes – hormonal transformation occurs, which in turn is responsible for stimulating the synaptic growth of the frontal lobe. This part of our brain enables neuropsychological maturation, for example, more complex emotional and cognitive functions.” 

UK researchers found that consuming mixed tree nuts, including walnuts, for four weeks could positively affect mood, memory and overall thinking capability. 

Walnut consumption has also been linked to other health benefits, such as lower risks of Type 2 diabetes, cardiovascular diseases and cancer. 

Recent research suggests that walnuts have heart health benefits as they influence the gut microbiome to naturally increase the production of the amino acid L-homoarginine in the body. 

By Jolanda van Hal