A simple breakfast addition improved reaction times, but its effects on memory took a more complicated turn.
Adding walnuts to breakfast could help people respond faster on mental tasks and learn information more effectively later in the day.
A generous handful produced small cognitive benefits over the following six hours, although memory performance varied with the timing of the tests.
Walnuts may influence how the brain directs attention and obtains the energy needed for demanding mental work.
Professor Claire Williams, study co-author, said:
“A handful of walnuts with breakfast could give young adults a mental edge when they need to perform at the top of their game.”
A breakfast boost
The research involved over 30 healthy young adults aged 18–30, who ate two different breakfasts on separate visits to the laboratory.
One contained 50 g of crushed walnuts mixed into muesli and vanilla yoghurt, while the other contained no nuts.
The breakfasts contained almost identical calorie and fat totals, with butter added to the comparison meal to help achieve this match.
Participants completed tests before breakfast and again two, four and six hours afterwards, while researchers also recorded their brain activity.
Faster thinking
After the walnut breakfast, participants responded faster on tasks involving attention, resisting distractions and switching between different mental rules.
These abilities form part of executive function, which helps us control our responses and adapt to changing demands.
The differences were modest, averaging around eight milliseconds on the attention test and 22 milliseconds when switching between rules.
Whether improvements of this size would make a noticeable difference outside the laboratory remains uncertain.
The memory findings were more complicated.
Two hours after eating walnuts, participants performed slightly worse when repeatedly learning and recalling a list of words.
By six hours, however, the pattern had reversed, with better performance after walnuts than after the comparison breakfast.
Sustaining mental performance
One possibility is that walnuts helped protect learning performance as the testing day wore on.
Repeated mental effort can make it harder to take in new information, so preserving the ability to learn could be useful even without improving every aspect of memory.
However, participants did not report feeling less mentally fatigued after walnuts, leaving this explanation unconfirmed.
Another possibility is that some benefits emerged gradually as nutrients were absorbed and processed.
Walnuts contain omega-3 fats, protein and plant compounds called polyphenols, which could contribute individually or together.
Changes in brain activity
Electrical recordings revealed differences in frontal and parietal brain activity after the two breakfasts.
These regions contribute to attention, memory and the control of behaviour.
The changes may indicate that walnuts altered how mental resources were allocated during the tests, although they do not establish precisely why performance improved.
Blood samples also showed slightly higher glucose availability and lower concentrations of circulating free fatty acids after walnuts.
Greater glucose availability might help fuel demanding mental work.
Related
The study was published in the journal Food & Function (Bell et al., 2025).
