Abstract: A substance is described which can prevent or treat a disease associated with the secretion of an acid. A calcium receptor activator is the active ingredient in a composition which promotes bicarbonate secretion in a gastrointestinal tract. Examples of the calcium receptor activator include ?-Glu-X-Gly, wherein X represents an amino acid or an amino acid derivative, ?-Glu-Val-Y, wherein Y represents an amino acid or an amino acid derivative, ?-Glu-Ala, ?-Glu-Gly, ?-Glu-Cys, ?-Glu-Met, ?-Glu-Thr, ?-Glu-Val, ?-Glu-Orn, Asp-Gly, Cys-Gly, Cys-Met, Glu-Cys, Gly-Cys, Leu-Asp, ?-Glu-Met(O), ?-Glu-?-Glu-Val, ?-Glu-Val-NH2, ?-Glu-Val-ol, ?-Glu-Ser, ?-Glu-Tau, ?-Glu-Cys(S-Me)(O), ?-Glu-Leu, ?-Glu-Ile, ?-Glu-t-Leu, and ?-Glu-Cys(S-Me).