Research published in the BMJ journal: Gut suggests that eating a Mediterranean diet can curb the advance of frailty and cognitive decline
The five-country study indicates that eating a Mediterranean diet for a year boosts the types of gut bacteria linked to ‘healthy’ ageing while reducing those associated with harmful inflammation in older people.
Promoting bacteria in the gut
As ageing is associated with deteriorating bodily functions and increasing inflammation, both of which herald the onset of frailty, the researchers realised that a Mediterranean diet might act on gut bacteria which can help to curb the advance of physical frailty and cognitive decline in older age.
Previous studies suggest that a poor and restrictive diet, which can often be the case among older people, particularly those in long term residential care, reduces the range and types of bacteria (microbiome) found in the gut and helps to speed up the onset of frailty.
Analysing gut microbiomes
The researcher team, 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 a 12 month period of either eating their usual diet (289 people) or a Mediterranean diet (323 people), rich in fruits, vegetables, nuts, legumes, olive oil and fish and low in red meat and saturated fats and specially tailored to older people (NU-AGE diet).
The participants lived in five different countries: France, Italy, Netherlands, Poland, and the UK and were either frail (28 people), on the verge of frailty (151 people), or not frail (433 people) at the beginning of the study.
Beneficial changes in the gut microbiome
Sticking to the Mediterranean diet for 12 months was associated with beneficial changes to the gut microbiome. 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 handgrip strength, and improved brain function, such as memory; and with reduced production of potentially harmful inflammatory chemicals.
A more detailed analysis revealed that the microbiome changes were associated with 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 which are linked to a heightened risk of bowel cancer, insulin resistance, fatty liver and cell damage.
Additionally, the bacteria that proliferated in response to the Mediterranean diet acted as ‘keystone’ species, meaning they were critical for a stable ‘gut ecosystem,’ pushing out those microbes associated with indicators of 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 findings were independent of the person’s age or weight (body mass index), both of which influence the make-up of the microbiome.
And while there were some differences in the make-up of a person’s gut microbiome, depending on the country of origin to start with, the response to the Mediterranean diet after 12 months was similar and consistent, irrespective of nationality.
Understanding the reason why is a complex issue
The researchers explain that the study findings can’t establish a causative role for the microbiome in health, added to which some of the implications are inferred rather than directly measured.
They emphasise “The interplay of diet, microbiome and host health is a complex phenomenon influenced by several factors,
“While the results of this study shed light on some of the rules of this three-way interplay, several factors such as age, body mass index, disease status and initial dietary patterns may play a key role in determining the extent of success of these interactions”
Although the researchers found a Mediterranean diet does promote healthy ageing, certain older people may have dental problems and/or difficulty swallowing, meaning that eating a Mediterranean diet may be largely impractical. However, the beneficial bacteria implicated in healthy ageing found in this study might yet prove useful therapeutic agents to ward off frailty, the researchers suggest.