There’s almost no function in the human body bacteria and their metabolites aren’t connected to. We couldn’t digest many foods without them. And forget synthesizing vitamins B and K. Scientists are constantly discovering new associations between our microbiome and our health. New findings around the gut-brain axis are emerging which indicate that our gut flora may even impact our mood, appetite, behavior, and circadian rhythm—functions we thought were relegated just to the brain. In fact, recent studies have linked poor microbiome health to symptoms associated with mental illness like anxiety, depression, and even autism spectrum disorder.