We all know that the Mediterranean diet - packed with fish, vegetables and olive oil - is good for us.
The eating regime, originating out of Italy and Greece, has long been linked to longevity.
However, a new study has found that it could also boost brain function - with four foods singled out as being particularly beneficial.
New research has shown that those who ate diets rich in vegetables, whole grains, olive oil and fish had the lowest risks of cognitive impairment.
The findings, published in the journal Alzheimer's and Dementia, discovered that fish and vegetables were especially linked to a slower rate of decline.
Crucially, scientists discovered that the Mediterranean diet even appeared to benefit participants with a higher genetic risk of Alzheimer's disease - those carrying the Apolipoprotein E (APOE) gene.
Dr Emily Chew, lead study author from the National Eye Institute in Maryland, United States, said: “Closer adherence to a Mediterranean-type diet was associated with lower risk of cognitive impairment but not slower decline in cognitive function.
"However, higher fish consumption was significantly associated with slower cognitive decline.
"APOE genotype did not influence these relationships."
The team aimed to analyse whether sticking closely to a Mediterranean diet would impact cognition.
Nine Mediterranean foods were analysed - including whole fruits, vegetables, whole grains, nuts, legumes, fish, and olive oil - as well as reduced consumption of red meat and alcohol.
The researchers assessed data from two large trials of nearly 8,000 people with varying severity of AMD, an age-related eye condition.
At the start of the study, both groups of participants were assessed for their diet.
The first set had their cognitive function tested using standardised tests at five years, while the second were tested more frequently, at two, four, and 10 years after the study’s start date.
A questionnaire completed by each participant provided the researchers with their average consumption of each Mediterranean diet component over the previous year.
Participants who stuck most closely to the eating regime had the lowest risk of cognitive impairment and higher performance on cognitive tests.
The evidence was strongest for those who maintained, but did not substantially alter their diet over the 10-year-period.
After the study period, participants who ate the highest fish consumption had the slowest rate of cognitive decline.
Dr Chew added: “These findings may help inform evidence-based dietary recommendations, adding strength to evidence that Mediterranean-type diet patterns may maximise cognitive reserve against impairment and dementia.”