EATING a Mediterranean-style diet in old age can curb frailty and cognitive decline by improving gut health, according to researchers.

Scientists followed more than 600 elderly people in the UK and Europe over the course of a year to determine what happened to the composition of bacteria in their digestive tract - the so-called microbiome - if they followed a diet rich in fruits, vegetables, nuts, legumes, olive oil and fish, but low in red meat and saturated fats.

Older people, especially those in long-term residential care, are more likely to have poor diets lacking in variety.

Such limited diets have been shown in previous studies to result in a loss of diversity in their gut bacteria, which is in turn linked to faster onset of frailty.

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In the latest research, microbiologists at University College Cork’s Microbiome Institute in Ireland split 612 participants aged 65 to 79 into two study groups.

They were drawn from the UK , France, Italy, the Netherlands and Poland.

The first group continued eating their normal diet, while the second group were placed on a specially-tailored Mediterranean diet, known as MedDiet.

At the end of 12 months, the Mediterranean diet was associated with stemming the loss of bacterial diversity, as well as an increase in types of bacteria which have been previously associated with signs of reduced frailty and better brain function, including better walking speed, hand grip strength, and memory.

Researchers also found a reduced production of potentially harmful inflammatory chemicals in participants on the Mediterranean diet, an increase in bacteria known to produce beneficial short-chain fatty acids, and a decrease in bacteria involved in producing particular bile acids.

Overproduction of the latter is linked to a heightened risk of bowel cancer, fatty liver, cell damage and insulin resistance potentially leading to diabetes.

In addition, the researchers found the types of bacteria that proliferated in response to the Mediterranean diet also played a critical role in driving out microbes associated with frailty.

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 authors, led by Dr Paul O’Toole, said their findings “support the feasibility of improving the habitual diet to modulate the gut microbiota which, in turn, has the potential to promote healthier ageing”.

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The results, published today in the journal Gut, were not affected by the participants’ age, gender or weight.

Despite differences in gut bacteria at the outset based country of origin, the response to the Mediterranean diet after 12 months was also consistent irrespective of nationality.

However, the authors noted there could be practical difficulties to improving elderly people’s diets, especially in settings such as care homes where many residents may have dental problems or difficulty swallowing solid foods.

They said: “[It] may be impractically expensive or logistically impossible in many countries where these ingredients are neither staple nor available year-round.

“In some older subjects with problems such as dentition, saliva production, dysphagia or irritable bowel syndrome, adapting a MedDiet may not be a realistic option.”

The latest research follows the results of a similar study - also published in Gut - which tested the same MedDiet on obese volunteers and found multiple positive changes in their microbiome regardless of calorie intake.