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NU-AGE MedDiet causes gut bacteria changes linked to improvements in cognitive function and memory, immunity and bone strength for healthy ageing

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, indicates a five-country study, published by Tarini Ghosh et al in Paul O’Toole’s group in the journal Gut.

As ageing is associated with deteriorating bodily functions and increasing inflammation, both of which herald the onset of frailty, this diet might therefore be acting on gut bacteria to help curb the advance of physical frailty and cognitive decline in older age, suggest the researchers.

Previous research suggests that a poor/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 and helps to speed up the onset of frailty.

The researchers therefore wanted to see if a Mediterranean diet might maintain the microbiome in older people’s guts and promote the retention or even the proliferation of gut 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 (n = 289) or a Mediterranean diet (n = 323), rich in fruits, vegetables, nuts, legumes, olive oil and fish and low in red meat and saturated fats, specially tailored to older people (NU-AGE diet).

The participants, who were either frail (n=28) on the verge of frailty (pre-frail; n=151) or not frail (n=433) at the beginning of the study, lived in five different countries: France, Italy, Netherlands, Poland, and the UK.

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 increased abundance of 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.

More detailed analysis revealed that the microbiome changes were associated with an increase in bacteria known to produce beneficial short chain fatty acids, by the fermentation of dietary fibre, and a decrease in bacteria involved in producing particular bile acids, overproduction of which is linked to a heightened risk of bowel cancer, insulin resistance, fatty liver and cell damage.

What’s more, the bacteria that proliferated in response to the Mediterranean diet acted as ‘keystone’ species meaning they were critical linkers in the scaffold of 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 country of origin, to start with, the response to the Mediterranean diet after 12 months was similar and consistent, irrespective of nationality.

This is a dietary intervention designed to investigate the effect of diet on the microbiome, and as such, can’t establish a causative role of the microbiome in health, added to which some of the implications are inferred rather than directly measured, say the researchers.

“The interplay of diet, microbiome and host health is a complex phenomenon influenced by several factors,” said Prof Paul O’Toole, leader of the research. “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.”

Older people may have dental problems and/or difficulty swallowing, so it may be impractical for them to eat a Mediterranean diet, but the beneficial bacteria implicated in healthy ageing found in this study might yet prove useful therapeutic agents to ward off frailty.

Reference: Mediterranean diet intervention alters the gut microbiome in older people, reducing frailty and improving health status: the NU-AGE 1-year dietary intervention across five European countries. Gut

PHOTO courtesy of Tomas Tyner, UCC  (left to right): Dr Tarini Ghosh, Ms Marta Neto and Prof Paul W. O’Toole APC Microbiome Ireland and School of Microbiology, University College Cork

LISTEN to Paul’s interview on RTE Drivetime (starts at 17.35)