Irritable Bowel Syndrome—How it Works

What Happens When You Have IBS

If you have IBS (irritable bowel syndrome), understanding what is happening in your body can help you identify triggers. Here’s what you need to know:

How Digestion Works

Let’s take a look inside your digestive system.

1. After you eat, food travels through your stomach and small intestine. Your body absorbs nutrients and sends the leftover waste to your colon (large intestine).
   
   
2. The muscles in your colon contract in a gentle, fixed rhythm to push the waste to your rectum.
   
   
3. Once the waste reaches your rectum, it leaves your body through your anus when you have a bowel movement.
   
   

When You Have IBS

1. The muscles in your intestines spasm, or contract longer and stronger than normal, usually in response to triggers. Common triggers include:
• Certain foods and drinks
• Large meals
• Stress
• Menstrual cycle (for women)
2. This reaction forces food through your intestines either too quickly (diarrhea) or too slowly (constipation).

If you have IBS, your digestive system reacts too strongly to triggers that don’t bother most people. Doctors don’t know exactly why. Figuring out what triggers your symptoms is key to getting them under control.

Learn More about IBS

• Irritable Bowel Syndrome Overview
• Irritable Bowel Syndrome Q&A
• IBS—Making the Diagnosis
• Controlling IBS Symptoms with Diet