Mediterranean diet promotes gut bacteria linked to 'healthy aging' in older people: Study

In a new five-country study published online in the journal Gut​, researchers looked at poor/restrictive diets, which are common among older people, particularly those in long term residential care. These limited diets reduce the diversity of gut bacteria, which speeds up the onset of frailty. 

The research 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 aging.

Researchers in Europe took on a study that investigated whether a year on the Mediterranean diet could in fact alter the gut microbiota and reduce frailty.

Method

Researchers analysed the gut microbiome of 612 people aged 65 to 79, before and after 12 months. The first group of 289 participants ate their usual diet, while 323 participants consumed a Mediterranean diet rich in fruits, vegetables, nuts, legumes, olive oil and fish and low in red meat and saturated fats. 

The participants consisted of 28 who were either frail, 151 were on the verge of frailty and 433 were not found to be frail at the beginning of the study. They lived in five different countries: France, Italy, Netherlands, Poland, and the UK.

Results 

Researchers found that consuming a Mediterranean diet was associated with beneficial changes to the gut microbiome.

Eating a Mediterranean diet for a year increases the kind of gut bacteria that is linked to healthy aging, while reducing those associated with harmful inflammation in older people.

The diet helps to stem the loss of bacterial diversity while increasing bacteria previously associated with several indicators of reduced frailty, such as walking speed, hand grip strength, memory as well as reduced inflammation. 

"The interplay of diet, microbiome and host health is a complex phenomenon influenced by several factors,​” the study noted.

Under the microscope

Upon further examination, the research revealed that the microbiome changes were associated with an increase in bacteria that produces beneficial short chain fatty acids. What's more, it decreased the type of  bacteria involved in producing certain bile acids. An overproduction of this kind can lead to increased risk of bowel cancer, insulin resistance, fatty liver and cell damage.

An increase in dietary fiber and vitamins and minerals, especially C, B6, B9, copper, potassium, iron, manganese, and magnesium, were largely behind the changes in the microbiome. 

The findings were independent of the person's age or body mass index, both of which impact the microbiome.

Despite the participant’s country of origin, the response to the Mediterranean diet after 12 months was similar and consistent, the authors pointing out:

“Notably, in spite of country-specific microbiome composition differences at baseline and different dietary adherences, the diet-responsive taxa identified across the entire cohort were largely shared across the different nationalities—that is, their association with diet was not specific for any country.”​

The authors also point out that some of the implications are inferred rather than directly measured. 

"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,"​ the authors explained, adding that the health benefits of the Mediterranean diet are not restricted to elderly subjects.

Source: Gut​

17 February 2020. doi: 10.1136/gutjnl-2019-319654​

“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”​

Authors: T. Ghosh et al.