 The investigators are involved in a research program to understand how different diets may affect the risk of colorectal polyps and cancer. To that end, the investigators are conducting a study of a western style diet versus a prudent style diet in which volunteer subjects are provided a different diet for 2 separate 4 week periods at the Rockefeller University Hospital. During one of these 4 week inpatient periods they receive a Western style diet and during the other 4 week inpatient period they receive a Prudent style diet. The investigators will determine changes within the colon as a result of the two different diets. A more detailed description of the study is provided below. 