The present invention regards an underpressure-activated valve mechanism for controlled dispensing of fluids, including liquid food articles, from a receptacle. When the user applies sufficient suction force (P2) across a pressure comparative diaphragm zone a valve opening force is applied to a valve area that has a force connection with the diaphragm zone. When the suction force ceases the valve area closes and remains closed, even in the event of overpressure (P3) in the receptacle.