Why do I spit up my food when I burp?

Regurgitation. When you burp, you are relaxing the lower esophageal sphincter (muscle at the bottom of the esophagus that keeps food and gas in the stomach for digestion). When this muscle opens to allow gas out, some food particles are also making their way across the sphincter and regurgitating up the esophagus. Antireflux medications can help but so can careful diet (no overeating, avoid sodas, late meals, etc.