The University of South Australia study, published in the journal Nutrients, also suggests that walnuts may counteract the effects of academic stress on the gut microbiota during periods of stress, especially in females.

Lead researchers, PhD student Mauritz Herselman and Associate Professor Larisa Bobrovskaya, say the results add to the growing body of evidence linking walnuts with improved brain and gut health.

“We found that those who consumed about half a cup of walnuts every day showed improvements in self-reported mental health indicators. Walnut consumers also showed improved metabolic biomarkers and overall sleep quality in the longer term.”

Students in the control group reported increased stress and depression levels in the leadup to exams but those in the treatment group did not. The walnut consumers also reported a significant drop in feelings associated with depression between the first and final visits, compared to the controls.

Previous research has shown that walnuts are full of omega-3 fatty acids, antioxidants, as well as melatonin (sleep inducing hormone), polyphenols, folate and vitamin E, all of which promote a healthy brain and gut.