Once again a study found that a diet rich in fruits, vegetables, whole grains, seeds, legumes, nuts, fish, and extra virgin olive oil is beneficial to the huge numbers of microbes living in our gut (the gut microbiome). This type of fiber-rich dietary pattern is generally called the Mediterranean diet.
The Mediterranean diet is associated with health in a number of ways: lower frailty in elderly persons, lowered risk of death and a number of diseases, as well as lowered levels of inflammation. Chronic inflammation is linked to cancers and a number of diseases - thus the goal is to keep inflammation levels down.
Researchers found that elderly persons eating a Mediterranean style diet for one year had beneficial effects on their gut microbes (after all, they were feeding the good gut microbes), which in turn resulted in less frailty, better cognitive function (including memory), and lower levels of chronic inflammation. There was an increase in beneficial microbes that are associated with health and lower levels of inflammation.
On the other hand, the group of persons eating their usual Western style diet (low in fiber, high in fats , meats, sugar, highly processed foods) did not show beneficial changes in their gut microbiome. They showed negative changes (deterioration) in the type of gut microbes, and also higher levels of chronic inflammation. After all, they were feeding the microbes associated with poor health and inflammation.
What was interesting was that they looked at the gut microbial communities of 612 persons (aged 65-79 years) who lived in five different countries (Poland, Netherlands, UK, France and Italy) - both at the start (baseline) and after a year. At baseline they could see that country-specific patterns in dietary habits were also reflected in the microbiome profiles.
And after a year there were similar positive changes in the gut microbes in all of those eating a Mediterranean style diet, especially with an increase in "keystone species" - those that are especially important for gut health, but also linked to better health and better cognitive (mental) functioning.
Some of the beneficial bacteria that increased in the Mediterranean diet group: Faecalibacterium prausnitzii, along with Roseburia (R. hominis), Eubacterium (E. rectale, E. eligens, E. xylanophilum), Bacteroides thetaiotaomicron, Prevotella copri and Anaerostipes hadrus. A majority of these species are associated with health benefits [e.g. production of short chain fatty acids (SCFAs) and lower risk of frailty] and with anti-inflammatory properties. They also are associated with a lower risk for diseases such as type 2 diabetes and colorectal cancer.
In contrast, the control group that ate a normal Western diet (fats, processed foods, low in fiber, high in meat and sugar) had an increase in Ruminococcus torques, Collinsella aerofaciens, Coprococcus comes, Dorea formicigenerans, Clostridium ramosum, Veillonella dispar, Flavonifractor plautii and Actinomyces lingnae. An increase in the abundances of R. torques, C. aerofaciens, C. ramosum and V. dispar have been associated with type 2 diabetes and colorectal cancer, atherosclerosis, cirrhosis, and inflammatory bowel disease.
A key finding was that the findings suggest that eating a Mediterranean style diet "modulates the microbiome in a direction positively associated with health". In other words, the benefit of the diet was that it fed beneficial gut microbes that improved health.
Note that these beneficial microbes are NOT found in any supplements or probiotics. You must eat the fiber-rich whole foods!
From Medical Xpress: Mediterranean diet promotes gut bacteria linked to 'healthy ageing' in older people
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 online 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 act on gut bacteria in such a way as 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 (microbiome) 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 proliferation of 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, and specially tailored to older people (NU-AGE diet).
The participants, who were either frail (n=28), on the verge of frailty (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 increase in 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 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.
What's more, 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 country of origin to start with, the response to the Mediterranean diet after 12 months was similar and consistent, irrespective of nationality.