Pistachios were shown to induce the strongest gamma waves, which are associated with improved cognition and learning.
Recently, a plethora of studies have pointed to the positive effects of nuts on cognition.
But how do nuts affect actual brain activity? Researchers from Loma Linda University (LLU) Health in California set out to investigate. They were led by Dr. Lee Berk, associate dean for research at the LLU School of Allied Health Professions.
Dr. Berk and his colleagues started from the observation that nuts have high concentrations of flavonoids — that is, antioxidants believed to have anti-inflammatory, anti-cancerous, and heart protective effects.
As the authors explain in their study, previous research has shown that flavonoids can enter areas of the brain's hippocampus that are responsible for learning and memory.
These flavonoids are thought to induce neuroprotective effects, leading to "neurogenesis," or the "birth" of new neurons, as well as improving the blood flow to the brain.
But how would these benefits translate into the brain's electric activity? The researchers wanted to find out, so they asked study participants who regularly consumed a variety of nuts to let an electroencephalogram (EEG) measure their brain activity.
Nuts induce strong gamma and delta waves
For their study, Dr. Berk and his colleagues used participants who regularly consumed almonds, cashews, peanuts, pecans, pistachios, and walnuts.
These participants were asked to let an EEG measure their brain waves as they were experiencing a "sequence of enhancing sensory awareness tasks ranging from cognition of past experience, visualization, olfaction, taste, and finally consumption of nuts."
These sequences were varied so that the EEG could measure wave band activity across nine different cortical regions.
"This study provides," the authors write, "objective evidence that [brain wave strength] for different brain EEG wave bands are modulated differentially by different types of nuts. These data appear to support an association of nuts' health benefits with an increase in [delta waves] and [gamma waves]."
More specifically, peanuts resulted in the strongest delta response, while pistachios produced the highest response in gamma waves.
Gamma waves are associated with perception, rapid eye movement (REM) sleep, and information processing and retention, and they are generally thought to improve cognitive processing.
Delta waves are linked with a healthy immune response and deep, or non-REM, sleep. Both delta and gamma waves were highest with pecan nuts.
The researchers also looked at the antioxidant concentration of each different kind of nut and found that walnuts had the highest levels of the substance, followed by pecans and cashews.
Overall, all six nut varieties had high levels of the beneficial antioxidants.
"This study provides significant beneficial findings by demonstrating that nuts are as good for your brain as they are for the rest of your body."
Dr. Lee Berk
Dr. Berk also hopes that future research will unveil further benefits of nuts on the brain and nervous system.
He is known for his previous research into the benefits of flavonoids in dark chocolate, as well as his studies on the health benefits of laughter and happiness.