Food matters: how the microbiome and gut-brain interaction might impact the development and course of anorexia nervosa

Abstract

Anorexia nervosa (AN) is one of the most common chronic illnesses in female adolescents and exhibits the highest mortality risk of all psychiatric disorders. Evidence for the effectiveness of psychotherapeutic or psychopharmacological interventions is weak. Mounting data indicate that the gut microbiome interacts with the central nervous system and the immune system by neuroendocrine, neurotransmitter, neurotrophic and neuroinflammatory afferent and efferent pathways. There is growing evidence that the gut microbiota influences weight regulation and psychopathology, such as anxiety and depression. This article reviews how the gut-brain interaction may impact the development and course of AN. A "leaky gut", characterized by antigens traversing the intestinal wall, was demonstrated in an animal model of AN, and could underlie the low-grade inflammation and increased risk of autoimmune diseases found in AN. Moreover, starvation has a substantial impact on the gut microbiome, and diets used for re-nutrition based on animal products may support the growth of bacteria capable of triggering inflammation. As there is currently no empirically derived agreement on therapeutic re-nourishment in AN, this review discusses how consideration of gut-brain interactions may be important for treatment regarding the determination of target weight, rapidity of weight gain, refeeding methods and composition of the diet which might all be of importance to improve long-term outcome of one of the most chronic psychiatric disorders of adolescence.

Keywords: Anorexia nervosa; Autoimmune disease; Gut–brain interaction; Microbiome; Starvation.

Fig. 1

Interaction between the gut microbiome and the brain. While food is one of the main influencing factors of the gut microbiome, the microbiome in turn is an important influencing factor of body weight. Multiple interactions link the microbiome with the brain: Gut originating fatty acids (SCFA´s), serotonin, brain-dervied neurotrophic growth facotr (BDNF), nervus vagus stimulation and inflammatory cytokines appear to impact the brain via various pathways and infuence mood and memory function. In turn, brain originating corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol influence the gut and its microbiome. In AN, a “leaky gut” seems to increase transfer of microbiotal antigens into the systemic circulation, further increasing inflammation and influencing interactions with the brain, potentially also affecting mood and memory function