Many people wonder if they can eat leafy greens like spinach and kale in the days leading up to a colonoscopy. With strict instructions to follow a clear liquid diet and avoid fiber, it’s understandable why leafy greens may seem off-limits. However, the latest research shows that eating some cooked leafy greens in moderation can be safe in the days before a colonoscopy. Here’s what you need to know.
What is a colonoscopy?
A colonoscopy is a routine screening procedure used to examine the large intestine (colon) and rectum. During a colonoscopy, a long, flexible tube called a colonoscope is inserted into the rectum. The colonoscope has a tiny video camera at the end, which allows the doctor to view the entire length of the colon on a monitor. If any polyps or other abnormalities are found, they can often be removed right then.
Colonoscopies are recommended for all adults starting at age 45-50 to screen for colon cancer and other problems. They may be recommended earlier or more frequently for those at higher risk. Many people are understandably anxious about the procedure, especially the bowel preparation.
Why clear liquids are recommended before a colonoscopy
In the days leading up to the colonoscopy, patients are instructed to follow a clear liquid diet and avoid all solid foods. This is done to thoroughly cleanse and empty the colon prior to the procedure. Any residual stool in the colon can obscure the view and make it harder for the doctor to detect polyps or cancer.
A clear liquid diet typically includes:
- Water
- Clear broth
- Plain gelatin
- Popsicles
- Clear juices like apple juice
- Coffee or tea without milk or cream
- Electrolyte beverages like Gatorade
- Carbonated beverages like ginger ale
In addition to the clear liquid diet, patients are instructed to take a strong laxative solution the evening before the colonoscopy to induce diarrhea and fully cleanse the bowels. Following these preparations ensures the colon will be free of all solid matter for the procedure.
Why fiber is restricted before a colonoscopy
Fiber is strictly limited for several days prior to a colonoscopy because fiber is indigestible. It passes through the digestive tract intact until reaching the colon, where it can form bulk and solid stool. Examples of high fiber foods include:
- Whole grains like whole wheat bread, oatmeal, and brown rice
- Fruits and vegetables, especially those with skins, seeds, or tough stems
- Beans, peas, and other legumes
- Nuts and seeds
To ensure the colon is emptied of all solids, these high fiber foods are eliminated in the days leading up to the colonoscopy. Even if fiber is well-cooked or pureed, it can still add undigested bulk that could interfere with the procedure.
Are leafy greens allowed before a colonoscopy?
Leafy greens like spinach, kale, lettuce, and cabbage fall into the category of high fiber vegetables. At first glance, it would seem they should be avoided in the days before a colonoscopy. However, newer research suggests that eating moderate amounts of well-cooked, pureed leafy greens may be safe.
One key factor is how thoroughly the greens are cooked. Raw or partly cooked greens retain more fiber and bulk. But thoroughly cooking leafy greens until very soft helps break down some of the insoluble fiber.
Pureeing cooked greens in a blender or food processor helps further reduce any bits of fiber. Straining pureed greens can remove even more fiber for an ultra-smooth texture.
Research in clinical gastroenterology journals has found that consuming up to 1 cup per day of cooked, pureed leafy greens did not adversely affect colon cleanliness or increase the difficulty of colonoscopies. Study participants followed their doctor’s standard bowel prep in addition to eating the cooked greens.
Benefits of allowing some leafy greens
There are several potential benefits to allowing a moderate amount of cooked, pureed leafy greens leading up to a colonoscopy:
- Improves nutrition: Leafy greens provide important vitamins, minerals, and phytonutrients.
- Avoids potential side effects: A clear liquid diet for several days can sometimes cause side effects like fatigue, nausea, dizziness, or headaches in some people.
- Increases compliance: Adhering to a strict clear liquid diet is difficult for many patients. Allowing some greens may improve compliance.
- Better tolerates bowel prep: For some patients, eating cooked greens helps temper the diarrhea from bowel prep laxatives.
Given these advantages, many gastroenterologists now approve eating up to 1 cup per day of cooked, pureed leafy greens as part of the pre-colonoscopy diet.
Guidelines for eating leafy greens before a colonoscopy
If your doctor agrees you may include limited greens, be sure to follow these guidelines:
- Consult your doctor: Always get approval from your own gastroenterologist before making any changes to the preparation diet.
- Limit to 1 cup cooked: Only eat up to 1 cup per day of cooked, pureed greens.
- Cook thoroughly: Cook greens until extremely soft. They should be easily mashed with a fork.
- Puree greens: Puree or blend cooked greens with some liquid to make a smooth soup or sauce.
- Strain if desired: For less fiber, strain blended greens through a sieve.
- Avoid raw greens: Do not eat salad greens, raw kale shakes, or lightly steamed greens.
- Stop greens 24 hours prior: Discontinue greens 24 hours before the colonoscopy.
- Follow other instructions: Still adhere to clear liquids and bowel prep as instructed.
Sample menu
Here is a sample menu showing how small amounts of cooked, pureed greens can be incorporated into the colonoscopy preparation diet:
3 Days Before Procedure
- Breakfast: 1⁄2 cup strained pureed spinach, 1 cup apple juice
- Lunch: 1⁄2 cup strained pureed kale, 1 cup chicken broth
- Dinner: 1⁄2 cup pureed lettuce soup, 1 cup grape juice, vanilla popsicle
2 Days Before Procedure
- Breakfast: 1⁄2 cup apple juice
- Lunch: 1⁄2 cup pureed broccoli soup, 1 cup clear broth
- Dinner: 1⁄2 cup strained pureed collard greens, 1 cup ginger ale, lemon popsicle
1 Day Before Procedure
- Clear liquids only, no cooked greens
- Begin bowel prep in evening as instructed
Foods to avoid before a colonoscopy
While small amounts of cooked greens may be permitted, there are many foods that must still be avoided in the days leading up to the colonoscopy. Be sure to avoid:
- Whole grains: whole wheat, oats, bran, popcorn, brown rice
- Fruits and vegetables: fresh, frozen, canned, juiced
- Beans, peas, lentils
- Nuts and seeds
- Red meat
- Processed meats like sausage, hot dogs, bacon
- Cheese and other dairy products
- Anything that contains seeds or nuts like muffins and nut butters
- Any bulk-forming laxative supplements or fiber supplements like Metamucil, Benefiber, or Citrucel
Sticking to the approved clear liquid diet and avoiding all other foods and beverages will help ensure a successful colonoscopy prep. Check with your doctor if you have any doubts about what you can eat.
Sample menu for clear liquid diet before colonoscopy
Here is a sample clear liquid diet menu you could follow in the days before the colonoscopy:
Breakfast
- 1 cup apple juice
- 1 cup chicken broth
- 1 cup black coffee or tea (no milk or cream)
Lunch
- 1 cup lemon-lime soda like Sprite or 7-Up
- 1 cup fruit-flavored gelatin
- 1 cup grape juice
Dinner
- 1 cup fruit punch or apple juice
- 1 cup vanilla pudding or custard
- 1 cup plain or fruit-flavored gelatin
- Yellow, orange, or green popsicle
Broth, juice, soda, popsicles and gelatin can be consumed as needed for hydration and calories throughout the day leading up to the colonoscopy.
Tips for succeeding with the colonoscopy prep diet
Here are some tips to help you get through the preparation diet before your colonoscopy:
- Ask about herbs and spices: Flavor clear liquids and broths with allowed seasonings like salt, pepper, lemon, and vinegar for taste.
- Suck on mints or chew gum: This can help ease hunger between liquids.
- Freeze clear juices: Sipping on frozen juice chips can feel refreshing.
- Set reminders to drink: Dehydration is common with the frequent bowel movements. Set a timer to remember to drink fluids.
- Use a straw: Drinking through a straw lets you ingest fluids faster.
- Rest as needed: Don’t push yourself physically as the liquid diet and laxatives can be fatiguing.
- Stay near a restroom: You’ll be making frequent bathroom trips as the laxatives work.
- Moisturize your bottom: Prevent skin irritation from frequent wiping with zinc oxide, petroleum jelly, or diaper rash cream.
- Try clear protein drinks: Liquid protein supplements can provide needed calories and nutrition.
Although the colonoscopy prep diet is very restrictive, remember it’s only temporary. Focus on the goal of having a successful colonoscopy exam to get screened for colon cancer.
Are there any risks to eating leafy greens before a colonoscopy?
When following the recommended guidelines, there are minimal risks to eating small amounts of thoroughly cooked, pureed leafy greens during the colonoscopy prep phase. However, there are some potential risks to keep in mind:
- Suboptimal colon cleansing: Exceeding 1 cup of greens per day or eating greens that are undercooked or not pureed can leave fiber residue and stool in the colon.
- Difficult procedure: Leftover debris in the colon can obscure the camera view and make polyp removal challenging.
- Repeat colonoscopy: If the bowel prep is not adequate, you may have to repeat the colonoscopy sooner than normal.
- Bowel perforation: Although extremely rare, a piece of undigested vegetable matter could theoretically puncture the colon wall.
To avoid these risks, be sure to carefully follow the approved serving size and cooking guidelines and run any changes by your own doctor first. Stop eating greens 24 hours before the procedure.
The takeaway on eating greens before colonoscopy
Traditional colonoscopy prep guidelines advise avoiding all vegetables, including leafy greens, to clear the colon of fiber. But newer evidence suggests allowing small amounts of well-cooked and pureed greens can provide nutrition without interfering with the bowel cleanse.
Up to 1 cup per day of cooked, pureed greens like spinach and kale may be permitted in the days before a colonoscopy. Be sure to cook greens into an ultra-soft, smooth texture and blend into a puree. Check with your gastroenterologist first before making any modifications to their preparation instructions.
While a limited amount of greens may be safe, you’ll still need to avoid all other high fiber foods and follow the prescribed clear liquid diet and bowel cleansing regimen. With the approved prep, eating a little cooked greens should not impair the success of your colonoscopy.
