Dietary Interventions and Brain–Gut Disorders

Several lines of evidence suggest that the gut microbiome may represent a valid target for new therapeutic interventions in relation to disorders of the gut–brain axis. Indeed, the concept of a microbiome–gut–brain axis has gained considerable traction in recent years. While several diseases and disorders may reflect disruption of, or dysfunction along, the microbiome–gut–brain axis this chapter will focus on one very common and challenging disorder long perceived as representing dysfunction along the gut–brain axis: irritable bowel syndrome (IBS). Recognizing the frequency with which patients report exacerbation of their IBS symptoms on eating there has been, of late considerable interest in diet in the treatment of IBS. A variety of dietary approaches have been advocated with the diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) achieving most traction. The physiological basis for its efficacy as well as evidence to support its efficacy are reviewed. While comparisons between the low FODMAP diet and other dietary approaches to IBS have yielded variable results, interest in the gluten-free diet has receded somewhat though it may be of benefit to certain select populations. Various therapeutic strategies have been employed to address gut microbial factors that may contribute to IBS and include probiotics, prebiotics, and postbiotics. With regard to prebiotics and probiotics, while a considerable volume of experimental data attests to their ability to address various pathophysiologic parameters relevant to IBS, the interpretation of clinical trials continues to pose challenges. Thus, while probiotics, in general, appear to be beneficial in IBS, less is known about ideal strain, preparation, and dosage; for prebiotics and postbiotics, data are scant but appear promising. More high-quality clinical trials are needed.