What Can You Eat When Preparing for a Colonoscopy?

If you are scheduled to have a colonoscopy, you may be dreading the test preparation, which involves following a special diet and drinking medications that help evacuate all stool from the intestines. Although each gastroenterology clinic provides their own, specific preparation instructions, the common dietary themes are to minimize fiber and dietary residue while staying hydrated, making it easier to have a clean colon on the day of the test.

A colonoscopy is an imaging test that examines the inside of the rectum and colon. For optimal visualization, fecal matter needs to be completely removed from the colon prior to this procedure. If the colon isn't adequately prepared, precancerous polyps or lesions could be missed or the exam may need to be rescheduled. So to prepare for the colonoscopy, your doctor or medical center will provide you with specific guidelines on how to eat and drink in the days prior to this test, and these steps will also explain how and when to take the bowel cleansing solution or laxative.

Most colonoscopy preparation instructions call for a low-fiber diet 3 to 4 days prior to the procedure, in order to minimize the amount of food residue in the colon. This diet may also be referred to as a low-residue diet, which is a bit different since this diet not only restricts high-fiber foods such as whole grains, nuts, seeds, dried fruit, or raw fruits or vegetables, but also limits milk products. Examples of acceptable low-fiber/residue food choices include soft, tender chicken or fish, eggs, tofu, white rice or pasta, potatoes, white bread or cream of wheat cereal, canned peaches or applesauce, and well-cooked vegetables such as carrots. Liquid nutrition supplements, such as Boost or Ensure, can also fit into this preparation diet.

According to the American Society for Gastrointestinal Endoscopy, most bowel preparation instructions call for a clear liquid diet starting the morning before the procedure. This liquid diet stops about 2 hours prior to the colonoscopy, when all food and drink is restricted. A clear liquid diet includes clear broth, clear juices without pulp, sports drinks, water, tea or plain jello. Clear liquid nutrition supplements are also available, such as Ensure Clear or Boost Breeze. Red, blue and purple liquids or gelatin should be avoided, because these pigments discolor the lining of the colon and may make it harder to find small polyps or lesions.

Most people find it challenging or burdensome to follow these bowel preparation instructions, including the day-long clear liquid diet. In fact, it's estimated that 20 to 30 percent of people do not adequately clean their bowels prior to their colonoscopy. This has prompted researchers to determine if different approaches work -- and the results should please anyone who dreads this test diet. This research, which has already made it's way into clinical practice guidelines, has shown that a low fiber/residue diet can be used the day before the colonoscopy, with results equal to that of a clear liquid diet. So don't be surprised if your doctor allows a variation from the norm -- such as low-fiber breakfast and lunch meals, but a clear liquid dinner on the day before the test.

Since each gastroenterology clinic may have different recommendations for colonoscopy preparation, be sure to receive your clinic's instructions before your preparation begins. Read these directions thoroughly and follow them closely. Purchase food and beverages items in advance to help you get though the preparation diet, and be sure your schedule allows the time and privacy for the preparation. Don't plan any extended travel, business meetings or physical exertion on your preparation day, as you will need to be close to a bathroom and may be hungrier that usual. If you have any questions about the preparation for your procedure, speak with the staff at your gastroenterology clinic.

Reviewed by Kay Peck, MPH RD