A reclosable bag has a bag body and a reclosable, zipper-type closure. The reclosable closure has extruded male and female interlocking profiles extending along opposing sides of an opening of the bag and are constructed to releasably interlock. The closure also has an extruded valve flange extending from one side of the closure to engage an opposing surface of the closure when the profiles are interlocked. The flange and opposing surface are constructed to separate in response to pressure within the bag for venting the bag with the profiles interlocked, and to increase a contact pressure therebetween in response to presence of a vacuum in the bag. The closure also defines a vent passage extending from an air space between the opposing sides of the opening and between the interlocking profiles and the valve flange. In use, the interlocking profiles are engaged to close the bag opening, and then the bag sides are compressed together to force entrapped air out through the vent opening, deflecting the valve flange away from its opposing surface.