Mediterranean diet linked to improvements in gut microbiome

New research has found that older people who adhered to a Mediterranean diet for a year had healthier gut microbiomes and better measures of frailty. Mediterranean-type diets, rich in vegetables, legumes, nuts, and whole grains and generally excluding red meat, have been the subject of numerous health and nutrition studies.

Existing research has found that many people who follow a Mediterranean diet may have better heart and metabolic health, live longer, and may even have better mental health.

A new study by specialists from institutions in eight countries, including the University of Bologna, in Italy, and University College Cork, in Ireland, is now added to the list of potential benefits of a Mediterranean diet.

The researchers, who report their findings in the journal Gut, worked with data from a cohort of more than 600 older adults in five countries. They found that across the spectrum, a Mediterranean diet appeared to improve the gut health of older people and reduce frailty.

The first author of the study is Tarini Shankar Ghosh, Ph.D, of the APC Microbiome Ireland research institute.

Seeking to reduce fragility

The study authors note that previous research has suggested that a simple dietary intervention, such as switching to a Mediterranean-style diet, could reduce frailty in older people.

This is important because brittleness involves the gradual breakdown of multiple systems at once, often with low-grade generalized inflammation further contributing to poor health.

To verify that switching to a Mediterranean diet could reduce measures of frailty, the researchers involved in the current study recruited 612 people aged 65 to 79 years.

Medical examinations showed that 28 of the study participants rated “frail”, 151 were on the verge of frailty, and 433 showed no signs of frailty.

Participants came from France, Italy, the Netherlands, Poland or the United Kingdom. Of the total number, 323 individuals (141 men and 182 women) agreed to follow a Mediterranean-type diet for 1 year, while the rest continued with their usual diets and acted as a control group.

The Mediterranean diet involved was rich in vegetables, legumes, fruits, nuts, olive oil, and fish. It featured very little red meat and little dairy or saturated fat.
Better bacterial diversity in the gut. To understand the effects of diet on the health of older people, the researchers began by examining the impact on gut health.

This was because previous studies suggested that older people, particularly those who live in residential care facilities, tend to have less healthy gut microbiota, possibly as a result of more restrictive diets. In turn, an unhealthy gut corresponds to poorer overall health and a faster onset of frailty in older adults.

When the researchers compared the gut microbiome compositions of participants who had followed a Mediterranean diet for a year with those of participants who had followed their usual diets, they found significant differences.
Related article> Mediterranean diet and heart health

Stool samples revealed that after 12 months on the Mediterranean diet, participants had better bacterial diversity in the gut, compared to peers in the control group.

Additionally, better gut bacterial diversity was associated with better markers of frailty, including better gait speed, better grip strength, and better cognitive functioning. Participants who had adhered to the Mediterranean diet also showed fewer markers of low-grade chronic inflammation.

Why Mediterranean Diets Can Be Beneficial

By taking a closer look at what was happening in the participant’s guts, the researchers found that improvements in health were associated with richer populations of bacteria that produce beneficial short-chain fatty acids, on the one hand, and a decrease in populations of bacteria that produce bile acids, on the other.

The researchers explain that when bacteria release too much of certain bile acids, it is associated with an increased risk of insulin resistance, fat accumulation in the liver, cell damage, and even bowel cancer.


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