It is well known that diet and gut health affect mental health symptoms such as stress-related disorders, depression and anxiety. Signalling between the gut and the brain includes communication via the immune system, central nervous system and the endocrine (hormonal) system which in turn impacts mood and behaviour. This “communication” is under the influence of the gut microbiota; the gut is home to hundreds of trillions of microorganisms which form part of the gut-microbiome-brain axis. The complex interactions involved are thought to be influential in conditions such as depression, schizophrenia, autism-spectrum disorders and ADHD. Measurement of food-specific IgG antibodies is used as a strategy for identifying foods as a starting point for an elimination diet. Dr Gill Hart explores the evidence behind a role for food-specific IgG-guided elimination diet in mental health.