Feeding gut microbes to nourish the brain: unravelling the diet–microbiota–gut–brain axis

The prevalence of brain disorders, including stress-related neuropsychiatric disorders and conditions with cognitive dysfunction, is rising. Poor dietary habits contribute substantially to this accelerating trend. Conversely, healthy dietary intake supports mood and cognitive performance. Recently, the communication between the microorganisms within the gastrointestinal tract and the brain along the gut–brain axis has gained prominence as a potential tractable target to modulate brain health. The composition and function of the gut microbiota is robustly influenced by dietary factors to alter gut–brain signalling. To reflect this interconnection between diet, gut microbiota and brain functioning, we propose that a diet–microbiota–gut–brain axis exists that underpins health and well-being. In this Review, we provide a comprehensive overview of the interplay between diet and gut microbiota composition and function and the implications for cognition and emotional functioning. Important diet-induced effects on the gut microbiota for the development, prevention and maintenance of neuropsychiatric disorders are described. The diet–microbiota–gut–brain axis represents an uncharted frontier for brain health diagnostics and therapeutics across the lifespan. This Review provides an overview of the interplay between host diet and the gut microbiota, and how this affects brain function.