Along with fiber and getting regular exercise, drinking enough water is the most important factor in relieving constipation. H2O is critical to help stool move easily through the colon. The colon's main job is to reabsorb water. If you're a bit dehydrated, your stool will be harder and more difficult to pass, says Dr. Blaney. Drink 8 to 10 glasses of water a day, recommends Dr. Sam, and fill up on foods with a high water content.