I hit a wall last October — flat, grey, unexplainable. When I tracked my eating, the pattern was obvious: two weeks of airport food, zero vegetables, zero care. My gut was wrecked. Turns out, so was my brain. The gut-brain axis is real, it's researched, and the 100 trillion microbes living in your digestive system are directly shaping your mood, anxiety, and mental resilience. Here's what the science says — and what I actually changed.