Participants who ate extra nuts had their memory skills improve on average Getty Images

A Mediterranean diet could help improve memory and cognitive abilities in older people when supplemented with extra olive oil and nuts, according to new research.

In the study, published in the journal of the American Medical Association's JAMA Internal Medicine, the supplemented Mediterranean diet was seen to counteract age-related cognitive decline. Many of the participants, aged between 55 and 80, saw their memories improve over the course of four years.

As dementia and heart diseases are linked, 447 volunteers considered at high risk of heart disease were singled out for the study.

Two groups were assigned to follow the Mediterranean diet, filled with vegetables and olive oil and low in meat and dairy, and told to add either five tablespoons of extra virgin olive oil a day or a handful of mixed nuts. The third group followed a low-fat diet.

The group that ate extra nuts performed better in terms of memory and the group given extra virgin olive oil performed better in tests that required quick thinking, according to the findings.

"Our results suggest that in an older population a Mediterranean diet supplemented with olive oil or nuts may counteract age-related cognitive decline," Dr Emilio Ros of the Institut d'Investigacions Biomediques at Hospital Clinic, Barcelona and colleagues wrote.

Just over 13% among those who took extra olive oil were diagnosed with mild cognitive impairment, while 7% of those eating nuts were diagnosed with mild cognitive impairment, reports NBC News.

Around 13% of those who ate neither developed memory loss.

Most participants in the low-fat-only group lost some memory and thinking skills, while those who got extra nuts had their memory skills improve on average.

The group who consumed olive oil also saw improved problem-solving and planning skills.

Lower rates of heart disease and stroke, and a lower risk of dying early, was also seen among those who consumed the olive oil or nuts compared with those on the low-fat diet.

The benefits of a low-fat Mediterranean diet have long been hailed. It can also help keep people younger for longer, said a University of Exeter study that found longer, healthier telomeres in those fed the diet.