Eating a Mediterranean diet promotes gut bacteria linked to healthy ageing and may help curb the advance of frailty and cognitive decline, according to new Irish-led research.
Harmful inflammation was also reduced in older people who followed the diet for a year, according to the five-country study.
As ageing is associated with deteriorating bodily functions and increasing inflammation, the diet might act on gut bacteria so as to help curb the advance of physical frailty and cognitive decline in older age, the researchers suggest.
Previous research suggests a poor or restrictive diet, which is common among older people, particularly those in long-term residential care, reduces the range and types of bacteria found in the gut – the microbiome – and helps to speed up the onset of frailty.
Stomach microbiome
The researchers at University College Cork therefore wanted to see if a Mediterranean diet might maintain the microbiome in older people's guts, and promote the retention or even proliferation of bacteria associated with "healthy" ageing.
They analysed the gut microbiome of 612 people aged 65 to 79, before and after 12 months of either eating their usual diet or a Mediterranean diet rich in fruits, vegetables, nuts, legumes, olive oil and fish and low in red meat and saturated fats.
The participants, who were either frail, on the verge of frailty, or not frail at the beginning of the study, lived in five different countries: France, Italy, the Netherlands, Poland and the UK.
Sticking to the Mediterranean diet for 12 months was associated with beneficial changes to the gut microbiome.
Dietary fibre
It was associated with stemming the loss of bacterial diversity; an increase in the types of bacteria previously associated with several indicators of reduced frailty, such as walking speed and hand grip strength, and improved brain function, such as memory; and with reduced production of potentially harmful inflammatory chemicals.
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 findings, published in Gut journal, were independent of the person’s age or weight, both of which influence the make-up of the microbiome.
There were some differences in the make-up of a person’s gut microbiome, depending on country of origin to start with, but the response to the Mediterranean diet after 12 months was similar and consistent, irrespective of nationality.
The study was carried out by researchers at APC Microbiome Ireland, a Science Foundation Institute Research Centre, at UCC.
