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You are more bacteria than you are human. Let that sink in. Your body contains roughly 38 trillion bacterial cells — compared to about 30 trillion human cells. You are literally outnumbered inside your own body. But here's where it gets wild — your gut bacteria controls your mood. About 90–95% of your body's serotonin — the "happiness chemical" — is produced in your gut. Not your brain. Your gut. Scientists now call the gut "the second brain." It has its own nervous system — the enteric ne