Heartburn occurs when acid moves from its natural place in the stomach up into the food pipe or esophagus. The result is burning pain under the breastbone or at the bottom of the esophagus.
After you eat or drink, it's normal for your stomach to produce acid to help digestion. But activities like overeating, eating too fast, and spicy or fatty foods, alcohol, tobacco and stress, among others, can result in excess acid. And that's where sour stomach or stomach upset (acid indigestion) comes in.
Other symptoms you could feel include general discomfort and an uncomfortable feeling of fullness.
The Body Mechanics
Normally, food passes through the esophagus into the stomach after it's swallowed. A circular band of muscle at the bottom of the esophagus, the lower esophageal sphincter, then closes and prevents food and stomach juices from re-entering the esophagus. If the sphincter relaxes abnormally or becomes weakened, stomach acid can wash back up (reflux) into the esophagus and cause irritation.
