13 June 2018

A diet for your microbes

Scientists from NSU conducted the largest study on the effect of diet on the gut microbiota

NSU Press Service

The question of what is proper nutrition and what effect certain dietary interventions have on the body is very much discussed these days.  However, most of the scientific research in this direction is devoted to the study of the effect of individual nutrients under strictly controlled conditions. At the same time, the question remains open, what changes occur in the human body, which begins to adhere to a healthy diet without changing the usual rhythm of his life.

To answer this question, a group of scientists from the Laboratory of Theoretical and Applied Functional Genomics of NSU, the Atlas research company and ITMO University conducted a study in which 248 volunteers followed the recommendations of a nutritionist for two weeks aimed at increasing the amount of useful plant fibers in food and reducing "empty" calories.

Scientists were interested in the effect of diet on the body in terms of changes in the composition of the bacterial community (microbiota) of the volunteers' intestines. To do this, two samples of microbiota were collected from each volunteer – before and after following the recommendations. These samples were analyzed using metagenomic DNA sequencing. The results of the study are published in the scientific journal Nutrients (Klimenko et al., Microbiome Responds to an Uncontrolled Short-Term Diet Intervention in the Frame of the Citizen Science Project).

Intestinal bacteria are mostly human symbionts: they protect us from infections, produce vitamins and butyric acid necessary for intestinal cells, decompose complex polysaccharides and participate in the formation of immunity. When the balance of the microbiota and the human body is disturbed, the number of opportunistic bacteria increases, causing inflammatory processes in the intestine and other health problems.

In a community, each microbe performs certain functions, being a link in a complex metabolic network, and the composition of nutrients coming from outside with food largely determines which microbes will gain a competitive advantage. On the other hand, often the state of health also affects the composition of the community: according to the human microbiota, it is possible to predict with relatively high accuracy the presence of diseases such as type 2 diabetes, coronary heart disease and inflammatory bowel diseases. The composition of the microbiota varies quite a lot in people and allows us to judge both their dietary preferences and their state of health.

The presence of fermenting bacteria that convert complex polysaccharides into short-chain fatty acids useful for humans is one of the important signs of a healthy microbiota. The study showed that when following the recommendations, there was a significant increase in the representation of these bacteria. This suggests that if a person changes his diet towards a healthy one even within just two weeks, a beneficial effect on the microbiota will be exerted.


However, against the background of an increase in the representation of microbes associated with a healthy state of the body, some destabilization of the intestinal community was also observed: it was primarily expressed in a slight decrease in its diversity. The more diverse a community is, the more resistant it is to external influences, such as stress or taking antibiotics.  The effect of reducing diversity that was observed in the study was quite small. Apparently, it is due to the fact that the microbiota did not have time to "recover" from a fairly rapid change in diet.

– The research materials formed the basis of the microbiota test, and the conclusion of the study is very practical: it is possible to improve the condition of the intestine by increasing the amount of dietary fiber. And it works not only in rigorous clinical trials, but also at home," he noted Dmitry Alekseev, Senior Researcher at the Laboratory of Theoretical and Applied Functional Genomics of NSU. 

Another interesting observation was that in different people, the microbiota reacted to the diet with different strength: in some people, the composition of the community changed more. The groups did not differ either in the nature of nutrition before the study or according to the recommendations of a nutritionist, however, they could be predicted with fairly high accuracy by the composition of the microbiota before the diet. This observation suggests that in order to increase the effectiveness of dietary recommendations, it is important to take into account not only the current nutrition of a person, but also the composition of his intestinal community.

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