For three or four days before the colonoscopy, start a low-fiber diet free of raw produce, dried fruits, seeds, nuts and whole grains. The day before the procedure, consume only clear liquids, as stated by Harvard Medical School.
The purpose behind dietary restrictions in the days leading up to a colonoscopy is to empty the colon. If solid foods are in the colon, it is possible for the technician to overlook lesions and polyps, which can develop into cancer if left untreated. The colonoscopy can also take longer than planned, which can cause complications. In some cases, the technician has to reschedule the procedure, which means that the patient has to go through the hassle of bowel preparation another time, notes Harvard Medical School.
During the day before and the day of the colonoscopy, it is important to stick to clear liquid foods. This includes clear juices, clear bouillon or broth, black coffee or tea, clear sports drinks, and sodas, as well as such foods as popsicles and Jell-O. For two hours before the actual colonoscopy, a complete fast is necessary. The doctor gives the patient a liquid preparation that causes diarrhea designed to clear out the bowel. Generally, the patient takes half the liquid the night before the colonoscopy and the rest about six hours before the procedure, as stated by Harvard Medical School.