What is the Gut-Brain-Microbiome axis?
The gut-brain-microbiome axis refers to the communication network that links the bacteria in our digestive system to the brain, shaping many aspects of how we feel and function. We know these microbes assist with digestion and help us “produce essential nutrients” (Vernimmen, 2024), yet growing research shows they also influence “our mood, our mental health, and how we perform on cognitive tests” (Vernimmen, 2024). Scientists call this constant back and forth “bidirectional communication” (Halverson and Alagiakrishnan pp. 1),
meaning the gut and brain send signals to each other rather than working separately. Because the microbiome behaves like a “virtual organ” (Halverson and Alagiakrishnan pp. 1) it can communicate through the vagus nerve and through systems involving “immune and inflammatory pathways, neurotransmitters, microbial by products, neuroendocrine signaling… and the stress response pathway” (Halverson and Alagiakrishnan pp. 1). One striking example comes from research by John Cryan showing that when microbes from individuals with depression were transferred into rodents, the animals developed “comparable symptoms” (Vernimmen, 2024), demonstrating how strongly gut bacteria can influence the brain. When this relationship is stable, it supports mood, behavior, and cognitive function, but when the microbiome loses balance, known as “dysbiosis” (Halverson and Alagiakrishnan pp. 1), the rise of harmful bacteria may “predispose or contribute to the development of various health conditions and illnesses” (Halverson and Alagiakrishnan pp. 1) In other words, the gut and brain are deeply connected, and what happens in one can meaningfully shape the other.