The gut microbiome and the brain.
Galland, Leo·Journal of medicinal food·2014
Your gut bacteria can communicate with your brain in several ways: they produce substances that trigger your immune system, create chemicals that affect your mood and sleep, and send signals directly to your brain through a major nerve called the vagus nerve. When the balance of gut bacteria is disrupted, this communication can go wrong and may contribute to problems like chronic fatigue, brain fog, and mood changes.