It is no longer a secret that the intestinal microbiome has a significant influence on health and that it makes sense to strive for a healthy composition of bacteria in the digestive tract. But which form of nutrition is the best calling card for this? Researchers have targeted the Mediterranean diet.
Older people may benefit from switching to a Mediterranean diet. According to a study, a diet rich in fruit, vegetables, nuts and fish changes the bacterial community in the intestine: healthy species thrive while those associated with aging and inflammatory processes decrease, scientists report in the specialist magazine «Gut». In another study, researchers found that a low-meat diet also lowers the risk of heart disease by altering the gut bacterial community. It was published in the Journal of the American College of Cardiology.
What did the researchers study?
The group led by Paul O’Toole from the University College Cork APC Microbiome Institute in Cork (Ireland) analyzed the composition of the intestinal bacteria before and after switching to a Mediterranean diet in elderly people from five European countries (France, Great Britain, Italy, the Netherlands and Poland). They wanted to track down a possible connection between a healthy diet, intestinal bacteria and frailty and mental abilities. In total, they looked at 612 people between the ages of 65 and 79.
The scientists prescribed 323 of them a Mediterranean diet for a year, i.e. a diet that is typical of the Mediterranean region. This includes lots of vegetables, legumes, fruits, nuts, olive oil and fish and little red meat, dairy and saturated fat. The remaining 289 subjects continued to eat as before.
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The composition of the intestinal bacteria changed
Before the start of the diet and a year later, the researchers broke down the intestinal bacteria and their respective proportion of the total microorganisms in the digestive tract – the microbiome. The same happened in the control group. At the beginning, the microbiomes of the subjects were very different and easy to differentiate according to the individual countries of origin. In the second study, the microbiomes of those on the Mediterranean diet all looked quite similar. They differed significantly from the composition of the intestinal bacteria at the beginning and in the control group.
It was not the diversity of the bacteria that changed, but the frequency with which individual genera and species could be found. For example, following a Mediterranean diet was the proportion of Faecalibacterium prausnitzii significantly increased, a bacterium previously associated with delayed onset of frailty. According to the researchers, other common bacteria are also known for their anti-inflammatory and other health-promoting properties.
Complex interplay of nutrition, microbiome and health
Species that are said to have a harmful effect on health, on the other hand, decreased. For example, those involved in the formation of certain bile acids. An overproduction of these substances is associated with the development of colon cancer, fatty liver and cell damage. Age and body mass index of the subjects did not affect the correlation found. However, the scientists claim that the study cannot prove that the composition of the intestinal bacteria actually has a causal effect on aging processes. The interaction of nutrition, microbiome and health is complex and influenced by many factors.
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In the second study, Lu Qi’s team at Tulane University in New Orleans used data from a survey of nurses’ health. They focused on trimethylamine N-oxide (TMAO), a metabolite produced by gut bacteria when red meat is digested. The TMAO level in the blood plasma was measured in two blood samples each from 760 women, taken ten years apart.
It was found that women suffering from coronary artery disease had higher TMAO concentrations and a higher body mass index. They also consumed a relatively large amount of animal products and few vegetables. The women with the largest increase in TMAO levels over a 10-year period had a 67 percent greater risk of developing coronary artery disease (CAD).
Commenting in the Journal of the American College of Cardiology, Paul Heidenreich of the Stanford University School of Medicine at Stanford writes: «The results of the study provide further evidence for the role of TMAO as a predictive biomarker for heart disease.»