Maintaining a Healthy Microbiome
A shift in the microbial balance away from a pattern associated with health is known as dysbiosis (Wischmeyer 2016; Lloyd-Price 2016; Chan 2013). A healthy microbiome is highly diverse and characteristically resilient to physiological stress; on the other hand, a dysbiotic microbiome is generally marked by smaller numbers of beneficial species, the presence of more species with disease-causing potential, and lower species diversity (Chan 2013).
Dysbiosis in the gut increases the risk of immune perturbations both inside and outside of the digestive tract (Brown 2017). In addition, gut dysbiosis has been associated with a growing list of chronic diseases and conditions that includes—but is not limited to—the following (Lloyd-Price 2016; Wang, Du 2017; Morris 2016; Potgieter 2015; Knight 2017; Strati 2017; Marasco 2016; Chen 2018; Distrutti 2016; Flowers 2015):
- autism spectrum disorders
- autoimmune diseases
- cardiovascular disease
- celiac disease
- chronic fatigue syndrome
- type 1 and type 2 diabetes
- inflammatory bowel disease
- irritable bowel syndrome
- multiple sclerosis
- neurological diseases
- cognitive and emotional health
Dysbiosis, Leaky Gut, and Systemic Inflammation
Imbalanced intestinal microflora can trigger chronic mucosal inflammation, which increases intestinal permeability and creates a condition known as leaky gut (van der Meulen 2016; Morris 2016; Nagpal 2017). Intestinal permeability is controlled by interactions between proteins on the surfaces of adjacent cells lining the intestinal wall, which form structures known as tight junctions. Zonulin is a protein that modulates these tight junctions, and increased zonulin levels in the circulation are considered to indicate an impaired intestinal barrier (Ohlsson 2017; Fasano 2012; Moreno-Navarrete 2012).
A leaky gut allows the absorption of small food components and bacteria, which can then trigger systemic immune activation and inflammation (van der Meulen 2016). Gut microbes and microbial products and toxins can also cross a leaky gut (Slyepchenko 2017; van der Meulen 2016). This can lead to immune and inflammatory activation in distant tissues and organs, and is thought to be an important mechanism in the development of autoimmune diseases and diseases related to systemic inflammation (Morris 2016; Slyepchenko 2017; Nagpal 2017; van der Meulen 2016).
Small Intestinal Bowel Overgrowth
While the colon (part of the large intestine) has a complex and diverse microbial community, comprising more than 70% of gut microbes (Ghoshal 2017), the healthy small intestine has a more limited microbiome (Ponziani 2016). Small intestinal bacterial overgrowth (SIBO) is a pattern of dysbiosis that is increasingly recognized as a cause of common digestive symptoms such as indigestion, bloating, flatulence, and disordered bowel function, and as a possible underlying feature of irritable bowel syndrome (Ghoshal 2017; Thompson 2016; Sachdev 2013). The most commonly studied antibiotic treatment for patients with SIBO is rifaximin (Xifaxan), a non-absorbable antibiotic. In addition, preliminary evidence suggests probiotic therapy, alone or in combination with rifaximin, may be helpful. Promising results have been reported from trials using probiotics containing Saccharomyces boulardii, or rifaximin together with Lactobacillus casei (Ghoshal 2017; Chedid 2014).