Lactase Deficiency and the Small Intestinal Microbiome

Eligibility Details: Patient ages 18-75 presenting for upper gastrointestinal endoscopy for any indication except those outlined in the exclusion criteria below at the IU GI Endoscopy Sites including: IU North Hospital, Glen Lehman Endoscopy Suite, Springmill/Beltway Surgery Center, IU Saxony, and Eskenazi Hospital will be eligible for participation. Participants should be willing and able to sign informed consent. Inclusion Criteria for Controls (Aim 1): Adult patients ages 18-75 years meeting basic eligibility criteria as listed above will be considered for inclusion. Participants should report no current or recent history of intolerance to and avoidance of dairy nor use of treatments and products for dairy intolerance. Inclusion Criteria for Patients with Self-Reported Lactose Intolerance (Aim 1): Adult patients ages 18-75 years meeting basic eligibility criteria as listed above will be considered for inclusion. Participants should report current or recent history of intolerance to and avoidance of dairy. Inclusion Criteria for Controls (Aim 2): All controls eligible for and completing Aim 1 will be considered eligible for inclusion. Participants should not meet any of the Aim 2 exclusion criteria. Inclusion Criteria for Patients with Self-Reported Lactose Intolerance (Aim 1): All patients with self-reported lactose intolerance eligible for and completing Aim 1 will be considered eligible for inclusion. Participants should not meet any of the Aim 2 exclusion criteria. Exclusion criteria (Aim 1): 1. Patients with known bleeding diathesis given the need for small intestinal mucosal biopsies. 2. Patients with known history of eosinophilic esophagitis, inflammatory bowel disease, chronic pancreatitis or pancreatic insufficiency, celiac disease, peptic duodenitis 3. Antibiotic-use within the last 30 days 4. Major abdominal surgery except appendectomy or cholecystectomy > 6 months prior to enrollment 5. Prior radiation therapy of the abdomen 6. Use of tobacco products within the last 3 months 7. Allergy to milk 8. Currently pregnant or breast-feeding 9. Patients taking anti-coagulant drugs Exclusion criteria (Aim 2): 1. Meeting any of the exclusion criteria as listed for Aim 1 2. Known diagnosis of disorders associated with abnormal GI motility (gastroparesis, amyloidosis, neuromuscular disease including Parkinson's disease, collagen vascular disease, chronic malnutrition, and uncontrolled thyroid disease) 3. History of small intestinal bacterial overgrowth 4. Active peptic ulcer disease noted at the time of endoscopy 5. Recent colonoscopy bowel preparation or colonic enema in the preceding 4 weeks 6. Chronic immunodeficiency or chronic infectious illness 7. Currently undergoing chemotherapy 8. Patients taking anti-coagulant drugs