This is a research study looking at the effect of 5-Hydroxy Tryptophan (5-HTP) on urine excretion of 5-Hydroxyindolacetic acid (5-HIAA). 5-HTP is a common over the counter product that is sold in natural food stores and via the Internet. Increased levels of 5-HIAA in the urine can be found in a specific type of cancer, called carcinoid tumor. This study will examine the effect of oral 5-HTP intake on 5-HIAA excretion. Understanding this effect may help to determine which tests should be done in a patient with increased 5-HIAA excretion who’s also taking 5-HTP.