What is Lower esophageal sphincter (LES)?

The lower esophageal sphincter (LES) is like a rubber band at the bottom of your throat that helps you keep food in your stomach.

Imagine you're eating a big sandwich, and after you swallow it, you don't want it to come back up, that's where the LES steps in. It acts like a gatekeeper: when you swallow, it relaxes so food can go into your stomach, and then it tightens again to keep everything inside.

Think of the LES as a door with a spring. When you eat, the door opens (the LES relaxes), letting food in. Then the spring pulls the door shut (the LES tightens) so your food stays where it belongs, in your stomach!

Sometimes this door doesn't close all the way, and that's why you might get heartburn or feel like food is coming back up, it's like the door is left ajar.