Hippocrates, who is considered father of modern medicine, in 400 BC claimed that, “All diseases begin in the gut”. Ancient Vedic texts proclaim, “As is the food, so is the mood”. Therefore, food as medicine and taking care of the gut was known to mankind from time immemorial. However, it’s only over the past couple of decades that the critical role the microbiota–gut–brain axis plays in health and disease is emerging in mainstream research. The brain–gut axis is a bidirectional communication system between the central nervous system (CNS) and the gastrointestinal tract.

Regulation of the microbiota–brain–gut axis is essential for maintaining homeostasis, including that of the CNS. The route of this communication is not fully elucidated but includes neural, humoral, immune, and metabolic pathways. Studies are revealing how variations and changes in the composition of the gut microbiota influence normal physiology and contribute to diseases ranging from inflammation to obesity.

Understanding microbiota–brain interactions is an exciting area which may contribute new insights into individual variations in cognition, personality, mood, sleep, and eating behaviour, and how they contribute to a range of neuropsychiatric diseases ranging from affective disorders to autism and schizophrenia.

A number of approaches have been used to interrogate this axis including the use of germ-free animals, probiotic agents, antibiotics, or animals exposed to pathogenic bacterial infections. The implications of gut brain axis are enormous as it would help us to understand our day-to-day mood swings to pathogenesis of serious disorders, and thus will lead to therapeutic strategies to correct these ailments.