Nutrition-mediated effects of the intestinal microbiota
- 15.12.2015
- English Articles
- Michael Blaut
Peer-reviewed | Manuscript received: May 05, 2015 | Revision accepted: September 16, 2015
Introduction
The digestive tract of humans and animals is one of the most densely populated microbial habitats. It harbors microorganisms that obtain their energy primarily through fermentation, which is due to the lack of oxygen in the intestines. For growth, the microorganisms depend on substrates that serve as a source of cellular constituents and energy. These substrates mainly come from foods and the host organism. Only those bacteria capable of using the substrates available in the intestine and of tolerating the physicochemical conditions therein will be able to permanently colonize this ecosystem. Thus, the initial colonization and diet are the primary factors responsible for the composition of the microbial community in the intestine, also referred to as intestinal microbiota or intestinal microbiome, whereas the latter term emphasizes the microbial gene repertoire.
The growing interest in the intestinal microbiome is due to its wide-ranging influences on the physiology of the host. The interactions between the host and his intestinal bacteria affect the entire metabolism and the immune system. It is therefore not surprising that many diseases are associated with an imbalance of the microbiome. However, whether disease development is caused by changes in the gut microbiome or whether changes in the microbiota are the result of the respective disease has not yet been fully clarified.
Summary
Recent studies show that the fetus already comes into contact with bacteria. However, the actual colonization of the infant intestine takes place during and following birth. A vast majority of the microorganisms in the human intestine are bacteria. Furthermore, lower concentrations of Archaea and eukaryotes (fungi) are also present. For the most part, commensal bacteria in the intestine use constituents of the host‘s diet for their own growth. The diet therefore has a significant impact on the bacterial composition.
The microbiota plays an essential role in maturation of the immune system and maintenance of its functions. Intestinal bacteria interact closely with the mucosal immune system. However, the intestinal microbiota does not cause a systemic inflammatory response as long as the intestinal barrier is not disrupted and intestinal bacteria are contained in the gut lumen. An imbalance between immune tolerance and immune response toward intestinal bacteria can promote the development of various diseases.
The interrelationships between the microbiota and various diseases are currently under intense investigation. It is well known that the microbiotas differ between healthy humans and obese individuals, and in those with chronic inflammatory bowel disease. Conversely, the intestinal microbiota exerts an influence on these diseases. There are also indications for the involvement of the intestinal microbiota in the development of other diseases.
Keywords: nutrition, fiber, fermentable substrates, intestinal microbiota, mucosal immune system, inflammatory bowel disease, obesity
