Normally, as food moves along the digestive tract, appropriate digestive juices and enzymes digest and absorb calories and nutrients. After being chewed and swallowed,the food moves down the esophagus to the stomach, where a strong acid continues the digestive process. The stomach can hold about three pints of food at one time.When the stomach contents move through the pylorus to the duodenum, the first segment of the intestine, bile and pancreatic juice speed up digestion. Most of the calcium and iron in the foods we eat is absorbed in the duodenum. The jejunum and ileum,the remaining two segments of the nearly 20 feet of small intestine, complete the absorption of almost all calories and nutrients. The food particles that cannot be digested in the small intestine are stored in the large intestine until eliminated.