Subjects with a history of inflammatory bowel disease (38), diabetes (39), previous intestinal surgery (40-42), cirrhosis (43-47), celiac disease, probiotic use, current proton pump inhibitor use (48-54), recent antibiotic use (past 3 months), history of bowel obstruction (55), narcotic use (56) or age greater than 65 years (57-63) will be excluded. Most of these conditions are known to influence enteric bacteria levels. Women of childbearing years will undergo pregnancy testing before participating in the study (See below for details on the pregnancy test used). Women with positive pregnancy tests will be excluded.