Your gut is more than digestion — it’s a dynamic ecosystem that controls inflammation, mental health, and even how your genes behave. Highlights Function Impact on You Key Insight Gut–brain axis Influences mood, anxiety, and cognition via neurotransmitter production ~90% of serotonin is made in the gut Immune regulation ~70% of your immune system resides in your gut lining Microbiome balance reduces systemic inflammation Metabolic control Gut bacteria regulate blood sugar, fa