what causes spit?
<answer> A valve between the esophagus and the stomach helps prevent food from coming back up and out of the stomach. In infants, this valve is not well developed and can more easily allow food to go back up the feeding tube and cause spitting up. <context> Spitting Up in Infants Causes. When we eat or drink, food passes down the feeding tube or esophagus and into the stomach. In the stomach, the food mixes with acids and passes slowly into the intestines for further digestion. A valve between the esophagus and the stomach helps prevent food from coming back up and out of the stomach. In infants, this valve is not well developed and can more easily allow food to go back up the feeding tube and cause spitting up.