The role of the large intestine is to eliminate wastes from undigested food matter as well as the resorption of the water found in food and in the digestive juices. This conservation of water helps prevent us from dehydrating. By reabsorbing water, it returns to the circulation and is available for use by the body's tissues. However, sometimes, too much water is resorbed and wastes begin to collect in the rectum, leading to constipation. This can be due to too little water consumed by the person, or not enough fiber and roughage in the diet. These items add bulk and stimulate peristaltic action, thus helping to move food through the digestive tract and wastes out of the digestive system in a timely manner. Therefore, it is very important to drink enough liquids and to eat a diet rich in fiber to prevent constipation. It is also important to eliminate solid wastes when a person feels the urge to do so, instead of holding those wastes in. This can also lead to constipation.
During constipation the large intestine is sucking too much water from the stool, in order to prevent constipation a person should eat a lot of greens as they are mostly made out of water and this could provide enough water to soften the stool, the person should also drink a lot of water.