The Science: The gut and the brain are physically connected by the Vagus nerve, a massive superhighway of information. Astonishingly, roughly 90% of your body's serotonin (the "feel-good" neurotransmitter) is manufactured in your gut, not your brain. When your microbiome is fed living, whole foods, it produces the chemicals that keep you focused and happy.

The Analogy: Your gut and your brain are co-pilots flying a plane. If the gut-pilot is drunk on processed food and sugar, he starts sending erratic, panicked signals to the brain-pilot. To keep the flight smooth and your mind clear, you have to feed the gut what it needs.