 This is a prospective, controlled, 4 days study. All procedures followed are in accordance with the ethical standards of the committee on human experimentation of the Rabin Medical Center, and in accordance with the Declaration of Helsinki. In the screening meeting the participant or the control will be told about the aims and nature of the study, and will be comprehensively informed about all procedures, anticipated results and risks. After agreeing to participate they will sign the informed consent. A medical history, family history and symptomatic questionnaire will be filled, and the participant will be scheduled for gastroscopy. After a night fast gastroscopy will be performed, biopsies will be taken as needed for the different protocols see below. Then gastric acid output, mucin output and alkaline tide studies will be performed. Blood will be drawn for gastro panel of BioHit, routine blood tests, B12, CEA, CA19-9, and CAG A serology. In another day, 13CUBT and IFOBT will be performed. 