Kaarel and Signe Adamberg, senior research fellows with the institute, noted in the March–April issue of Horisont that the second genome of a human is the microbiome – the ecosystem of trillions of all kinds of micro-organisms (mostly bacteria) coexisting in and on our bodies.
While it is difficult to change our own genome, the intestinal microbiome can be influenced by lifestyle choices, including the diet, on the daily basis. The type of nutrients that reach the large intestine, which is inhabited by more than 95% of the population of micro-organisms in the whole body, is of critical importance. The part of our food that is not degraded by human digestive enzymes and thus not absorbed in the small intestine, reach the colon and serve as important nutrients for the colon microbes that are “powerful” enough to metabolize these complex substances.
The main nutrients essential for the microbiota, comprise of different fibres (complex carbohydrates). “When we eat, we also feed billions of bacteria living in our intestines. Knowing the amount and composition of food and the composition of intestinal microbiota, we can predict the impact of the food on the activity and energetics of colon microbial consortia,” Adamberg explains.
“The bacterial consortia break down a variety of fibres generating different organic acids and gases, as well as vitamins and bioactive substances essential for the host. In return, human receives energy as a result of this process – for example, the epithelial cells covering the intestinal walls obtain up to 70% of the required energy from organic acids produced by bacteria. Active epithelial cells, in turn, produce nutrients, for example mucins for the microbiota.”
“From low-fibre food, most nutrients are degraded and absorbed already in the small intestine. Bacteria in the large intestine are therefore left to “starve” and they start digesting their host, or the protective mucous layer covering the surfaces of intestines. Long-term “starving” the microbiota by sustaining a refined, highly processed diet low in fibres and high in simple sugars may be regarded as one of the reasons, besides decreased physical activity, changed life environment and increased use of drugs, especially antibiotics, why the incidence of life-style diseases, such as autoimmune diseases like allergies, and asthma, but also diabetes, different inflammations etc. is increasing in the modern society. In the worst case, ulcers or severe inflammations may develop in the intestinal tract,” asserts Adamberg. “If the menu includes foodstuffs high in fibres – wholemeal products, seeds, legumes, vegetables and fruits – a significant portion of the diet will also reach the large intestine to nourish the microbiota and benefit the host.”
Experiments with mice have shown the irreversible decrease of the diversity of gut bacteria by chronic lack of dietary fibres. The same is probably happening with humans who are only having a refined diet. It is obvious that the diversity of gut microbiota is related to the variability of our diet, our wellbeing and health.
The translation of this article from Estonian Public Broadcasting science news portal Novaator was funded by the European Regional Development Fund through Estonian Research Council.