The rapid diarrhea that patients experience who have diarrhea occurring after eating specific foods may be causing a "physiologic gastric dumping syndrome". This means that rather than the food being kept in the stomach for normal digestion, it rapidly goes into the small intestine and diarrhea occurs. This study is designed to measure how fast the food empties from the stomach when a person with this problem consumes a "regular diet", compared to a meal with a "triggering substance". Each participant will swallow a radio frequency capsule that with the different meals that will show how fast the food is traveling through the intestines in the different situations.