- 1=FGID group: Subject with any disease/disorder which can interfere with the gas collection; Subject with any antecedents of digestive surgery; Subject with any intake of antibiotics in the previous 2 months; Subject with any current use of any medication with potential central nervous system effects (except for chronic treatment with anxiolytics and antidepressants started at least 3 months before inclusion in the study); Subject taking drugs that might modify gastrointestinal function (except for chronic treatment with laxatives, started at least 3 months before inclusion in the study) ;