Mediterranean diet promotes gut bacteria linked to ‘healthy aging’ in older people

A study published in the journal Gut suggests that eating a Mediterranean diet for a year may boost the types of gut bacteria linked to “healthy” aging while reducing those associated with harmful inflammation in older people. As aging 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 weakness and cognitive decline in older age, suggested the researchers.

The researchers analyzed the gut microbiome of 612 people aged 65–79, 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, specially tailored to older people. 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, Netherlands, Poland, and the United Kingdom.

The researchers found that adhering to the Mediterranean diet for 12 months was associated with beneficial changes to the gut microbiome, stemming from the loss of bacterial diversity and the increasing abundance of bacteria previously associated with indicators of reduced frailty and improved brain function. Finally, there was a reduction in the 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 fiber, 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. The changes were primarily driven by an increase in dietary fiber and associated vitamins and minerals—specifically, C, B6, B9, copper, potassium, iron, manganese, and magnesium.

“The interplay of diet, microbiome, and host health is a complex phenomenon influenced by several factors,” concluded the authors. “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.”

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