You may not give your gut much thought beyond how much your stomach might be rumbling or whether your waistline looks a little bloated over your skinny jeans. But your gut is much more than a depository for your last meal—it’s home to microbes and bacteria that play a crucial role in everything from absorbing nutrients and boosting immunity to reducing inflammation and even balancing your mood. 

“Your gut, and the microbiome it contains, is extremely important to your overall health,” explains Raphael Kellman, M.D., founder of the Kellman Center for Integrative and Functional Medicine in New York and author of The Microbiome Diet. The microbiome is a miniature world inside your gastrointestinal tract that makes up 90% of the cells in your body.

“The microbiome plays an important role in immunological function, brain health, energy levels, skin, and muscle function,” Kellman says. “When your gut is healthy, the rest of your body is better for it.” Here’s why a healthy gut is good for you, and how you can keep it working at optimal levels.