Boys and girls who eat a handful of walnuts a day, or at least three times a week can have substantial improvements in cognitive abilities, including attention, suggests a study led by Spanish researchers.

The study, published in the journal eClinicalMedicine, showed that eating walnuts on a regular basis could benefit the cognitive development of adolescents and contribute to their psychological maturation.

While previous studies have shown the effect of nuts on brain health, the impact of their consumption at such a critical stage for cognitive development as adolescence has never been examined, claimed researchers, including from the Institut d'Investigacio Sanitaria Pere Virgili (IISPV).

Walnuts are rich in alpha-linolenic fatty acid (ALA), a type of omega-3 that plays a fundamental role in brain development, especially during adolescence.

"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 is what enables neuropsychological maturation, i.e., more complex emotional and cognitive functions. Neurons that are well nourished with this type of fatty acids will be able to grow and form new, stronger synapses," said Jordi Julvez, principal investigator from the IISPV.

The team included 700 secondary school students between 11 and 16 years of age from 12 different high schools in Barcelona. The control group received no intervention of any kind, but the experimental group received sachets containing 30 grams of walnut kernels. The young participants were asked to consume them daily for six months.

The team found that adolescents who ate walnuts for at least 100 days (not necessarily continuously every day) increased their attention functions, and those who had some symptoms of attention deficit hyperactivity disorder (ADHD) improved their behaviour significantly -- in class, they paid more attention to the teacher and were less hyperactive.

"The 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," the team said

This study demonstrates that following a healthy diet is as important as maintaining these habits over time and not abandoning them for adolescents to develop correctly on a cognitive and psychological level.

"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. Adolescence is a period of great brain development and complex behaviours that requires a significant amount of energy and nutrients," said Ariadna Pinar from the Institute.