Bacterial overgrowth: nutrition as part of the therapeutic concept

Peer-reviewed | Manuscript received: May 11, 2016 | Revision accepted: January 7, 2017

Small Intestinal Bacterial Overgrowth (SIBO)

Introduction

Humans live in a state of constant symbiosis with their intestinal microbiota, which is largely made up of bacteria. Its main characteristics are a high density, a high level of diversity and complex mechanisms of interaction. The majority of bacteria is found in the large intestine, where they play a critical role in digestion, synthesis, and absorption of nutrients. Studies have shown that nutrition is a major impacting factor on the composition of the microbiota, and therefore also greatly influences its characteristics (current overview in [1]).

Bacterial overgrowth is characterized by a change in the microbial colonization of the small intestine, which usually has few microorganisms (Small Intestinal Bacterial Overgrowth [SIBO]). It is not to be confused with dysbiosis, which is the term for an altered composition of the microbiota in the large intestine when there is a disease or clinical symptoms at the same time. Bacterial overgrowth was initially linked to abnormal anatomy or impaired motility of the gastrointestinal tract (GIT), and was defined in a quantitative manner, using an assessment of the number of bacteria. However, SIBO is now also being linked to various other factors, and particularly to functional diseases of the GIT, such as irritable bowel syndrome (IBS). This raises the question whether the composition or characteristics of the small intestinal microbiota are the determining factors for disease and whether the quantitative definition might be too simplistic.Whilst there are already several nutrition therapy approaches for treating dysbiosis in the large intestine (such as administering synbiotics and probiotics), the dietary interventions that can be applied to SIBO are currently limited to balancing out any nutritional deficiencies.

Abstract

Small Intestinal Bacterial Overgrowth (SIBO) is a heterogeneous disorder that is characterized by a quantitative and/or qualitative change in the microorganisms present in the small intestine, which usually has few microorganisms. This bacterial overgrowth is not to be confused with dysbiosis, which is the term for an altered microbiota in the large intestine when there is a disease or when there are clinical symptoms. Originally, it was linked to a postoperative anatomical context. However, today, it is also increasingly associated with functional diseases of the gastrointestinal tract, such as irritable bowel syndrome and other diseases. In this context, it is assumed that it is rather the composition of the bacterial species that is more crucial than the number of bacteria. Thus, factors affecting the microbiota are now coming into focus as possible risk sources as well as potential treatment approaches. Alongside traditional therapy, special nutrition could be effectively applied to re-establish a healthy microbiota, reduce bacterial gas formation, and prevent relapse. Avoiding rapidly fermentable carbohydrates, stimulating bile acid secretion and immunoglobulin release, along with selectively growing favourable microbiota are the first-line approaches to dietary intervention.

Keywords: bacterial overgrowth, SIBO, nutrition therapy, microbiota, small intestine

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