Fiber, particularly insoluble fiber, is linked with prevention of chronic constipation. Insoluble fiber from food acts like a sponge. Adding water to the “sponge” makes it soft and easy to push through the gastrointestinal tract. Insoluble fiber comes mostly from vegetables, beans, brown rice, whole wheat, rye, and other whole grains. Switching from refined grains to whole grains (e.g., from white rice to brown rice) often helps relieve constipation. It is important to drink lots of fluid along with the fiber—at least 16 ounces (480 ml) of water per serving of fiber. Otherwise, a “dry sponge” is now in the system, which can worsen the constipation.