Dr Shannon told The Telegraph that few people in the study got a perfect score for adherence to the Mediterranean diet but adopting even just a few Mediterranean-style culinary habits was beneficial.
“Individuals who had the highest level of adherence to the Mediterranean diet tended to eat a diet which was rich in fruits and vegetables (two or three portions of each per day), and contained moderate amounts (around three portions of each per week) of fish and other seafood, pulses/legumes and nuts,” he said.
“In addition, these individuals tended to use olive oil as their main cooking fat and consumed a moderate amount of wine (around seven small glasses per week).
“The diets of these individuals also tended to be lower in foods which are more traditionally associated with a classic Western diet like red and processed meat, sugar-sweetened drinks, sweets/pastries and butter/margarine.
“In contrast, the individuals with the lowest level of adherence to a Mediterranean diet tended to consume less fruits and vegetables, nuts, legumes and fish and contained more red and processed meat, sugar sweetened drinks, and sweets/pastries.
“It is important to note that few individuals had perfect adherence to a Mediterranean diet and our results suggest that even one or two small changes to an individual’s diet could make a big difference.”
However, some scientists have questioned the methodology of the study. Prof David Curtis, Honorary Professor at UCL Genetics Institute, questioned whether the observational findings could be explained by people with a Mediterranean diet being fitter overall, and not as a direct consequence of their food choices.
“It is not clear that a [Mediterranean] diet itself reduces dementia risk, although it is plausible that it might do so,” he said.
“In my opinion if there is an effect of diet then it is more likely to be on cardiovascular health in general and hence to impact dementia due to vascular disease rather than Alzheimer’s disease.”
He also called it “disappointing” that the study only included white participants and excluded other ethnicities.
Dr Susan Mitchell, head of Policy at Alzheimer’s Research UK, said: “There is a wealth of evidence that eating a healthy, balanced diet can help reduce the risk of cognitive decline. But evidence for specific diets is much less clear cut.
“While there are no sure-fire ways to prevent dementia yet, a diet rich in fruit and vegetables, along with plenty of exercise and not smoking, all contribute to good heart health, which in turn helps to protect our brain from diseases that lead to dementia.”
The study was published in BMC Medicine.