A Mediterranean diet with additional olive oil or nuts may improve thinking and memory in older adults, research suggests.

Scientists looked at the effects of different kinds of diet in 334 men and women whose average age was around 67.

Compared with a low-fat diet, a Mediterranean diet supplemented with nuts was associated with improvements in memory.

Adding extra olive oil to a Mediterranean diet appeared to improve thinking ability involving the brain’s frontal lobes.

However Alzheimer’s Research UK pointed out that the effects were very subtle and more work was needed before any conclusions could be drawn.

Simon Ridley, the charity’s head of research, said: “This study looked at a relatively small subset of people involved in a larger trial, but this trial was not designed to assess the effects of diet on memory or thinking, and these results should therefore be treated cautiously.

“It’s important to note that the people in this study did not have dementia, and this trial does not tell us whether a Mediterranean diet could prevent the condition.

“These findings suggest a need for much larger trials to understand better the effects of changes in diet on memory, thinking and dementia risk.”

The research is published online in the journal Jama Internal Medicine. The authors, led by Emilio Ros, from the Instuto de Salud Carlos III in Madrid, Spain, wrote: “Our results suggest that in an older population a Mediterranean diet supplemented with olive oil or nuts may counteract age-related cognitive decline.

“The present results... are encouraging but further investigation is warranted.”

A Mediterranean diet is typically based on vegetables, fruits, nuts, beans, cereal grains, olive oil and fish.