A diet of clear liquids maintains vital body fluids, salts, and minerals; and also gives some energy for patients when normal food intake must be interrupted. Clear liquids are easily absorbed by the body. They reduce stimulation of the digestive system, and leave no residue in the intestinal tract. This is why a clear liquid diet is often prescribed in preparation for surgery or a procedure , and is generally the first diet given by mouth after surgery. Clear liquids are given when a person has been without food by mouth (NPO) for a long time. This diet is also used in preparation for medical tests such as sigmoidoscopy, colonoscopy, or certain x-rays.
A clear liquid diet is not adequate in calories and nutrients. It should not be used for more than five days unless high-protein gelatin or other low-residue supplements are added.