Researchers have found a Mediterranean diet could help older people stave off frailty and keep mentally sharp.

A diet rich in fruit and vegetables, olive oil and fish was found to boost bacteria in the gut linked to healthy ageing, and reduce bacteria linked to inflammation.

Experts from the United Kingdom, France, Italy, the Netherlands and Poland found following this type of diet could help curb frailty and cognitive decline.

Previous studies suggest a restrictive diet, common in older people, reduces the diversity of microbiome in the gut.

These researchers determined if following a Mediterranean diet for a year could improve participants’ microbiome.

They analysed the gut microbiome of 612 people aged between 65 and 79, in the five countries before and after a year of sticking to their existing diet or switching to a Mediterranean one.

Participants were classed as frail, on the verge of frailty or not frail.

The new diet was rich in fruits, vegetables, nuts, legumes, olive oil and fish and low in red meat and saturated fats.

Sticking to the Mediterranean diet for 12 months was associated with beneficial changes to the gut microbiome and stemming the loss of bacterial diversity.

The researchers observed an increase in the types of bacteria previously associated with indicators of reduced frailty, such as walking speed and hand grip strength and improved brain function, such as memory.

Following the diet was also associated with reduced production of potentially harmful inflammatory chemicals.

The researchers said the most striking finding was the consistency of associations of the diet-modulated microbiome markers with biological markers of ageing, independent of nationality.

“We showed that they were not only associated with dietary compliance but were consistently associated with frailty and inflammatory markers, thereby confirming their importance for health maintenance independent of … age, body mass index and gender,” the researchers wrote.

The changes were largely driven by an increase in dietary fibre and associated vitamins and minerals, specifically C, B6, B9, copper, potassium, iron, manganese and magnesium.

The microbiome changes were linked to a decrease in bacteria involved in producing some bile acids, which are linked to an increased risk of bowel cancer, insulin resistance, fatty liver and cell damage when overproduced.