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It’s not the colonoscopy itself that most people are afraid of or anxious over — it’s the preparation.

Understandably, the colonoscopy prep diet process can be more uncomfortable than the procedure itself.

However, preparation is necessary to ensure a safe and successful colonoscopy.

This article explains the purpose of the colonoscopy prep diet, what foods to eat and avoid leading up to the procedure, and provides a sample colonoscopy prep diet menu.

colonoscopy prep diet

What is a colonoscopy?

A colonoscopy is a procedure that allows a doctor to view your colon or large intestine using a flexible camera called a colonoscope (1).

The procedure is commonly performed to screen for colorectal cancer.

The United States Preventative Services Task Force (USPSTF) recommends that all adults aged 45 to 75 years be screened for colorectal cancer and undergo a colonoscopy every 10 years thereafter (2).

Beyond its use for diagnosing colorectal cancer, it can also be used to diagnose, treat, or plan for surgical interventions for inflammatory conditions like diverticulitis, Crohn’s disease, and ulcerative colitis (1).

Before receiving a colonoscopy, bowel preparation is needed.

Bowel prep ensures that your colon is empty and mostly free of stool so that the doctor can clearly view the colon lining.

Without a clear view, the procedure can take longer, there’s a greater risk of complications, and it’s more difficult for the doctor to identify potential cancer or signs of diseases (1).

In some instances, a colonoscopy may need to be stopped and rescheduled if the bowel is not adequately cleansed.

Unfortunately, inadequate bowel preparations occur 10–25% of the time, in part due to poor compliance with the colonoscopy prep diet (3, 4).

Colonoscopy prep diet

For many years, the standard protocol for a colonoscopy prep diet would involve following a low-residue diet 3–5 days prior to a colonoscopy and a clear liquid diet the day before (3).

A low-residue diet — also known as a low-fiber diet — limits foods that contain fiber so that you have smaller and fewer bowel movements.

A clear liquid diet allows only clear liquids such as broths, popsicles, and tea or coffee with no added milk or cream.

Its purpose is to clear your bowels out, even more, leaving behind no undigested residue.

However, this protocol is very strict and makes the preparation process difficult to follow.

Although some doctors still prescribe the low-residue diet for several days leading up to the procedure followed by a clear liquid diet the day before, current evidence suggests this protocol is unnecessary.

To this point, multiple meta-analyses involving nearly 50 studies have shown that a low-residue diet is just as effective as a clear liquid diet for achieving adequate bowel preparation before a colonoscopy (5, 6, 7).

These studies also showed that patients experienced fewer side effects such as nausea, vomiting, and hunger compared with a clear liquid diet.

It’s also unnecessary to follow the low-residue diet for several days.

One study showed that a 3-day low-residue diet did not improve colonoscopy preparation results compared to a 1-day low-residue diet (8).

Based on these findings, current guidelines recommend following a low-residue diet only the day before a colonoscopy (9).

Colonoscopy prep drink

A bowel cleansing drink containing a laxative is also part of the colonoscopy prep diet process.

For a morning colonoscopy, current guidelines recommend a split-dose regimen, which involves drinking half the solution the evening before the colonoscopy and the second half the day of the procedure — usually, several hours before (9).

The alternative is to consume the entire solution — which is around 2 liters or 8.5 cups — the evening before.

This day-before regimen is associated with a lower quality bowel preparation and more side effects such as nausea, vomiting, and sleep disturbances than the split-dose regimen (10).

For an afternoon colonoscopy, a same-day preparation may be needed.

After your colonoscopy, you can usually resume your regular diet.

However, if you cannot tolerate your usual diet after, you may have to drink lots of fluids and eat soft, easily digestible foods like toast, eggs, bananas, and cooked cereals.

Low residue diet foods to eat and avoid

A low fiber diet restricts fiber to 10 grams of fiber per day (11).

Foods to avoid

Limit these fiber-rich foods the day before your colonoscopy:

  • Vegetables: raw or undercooked vegetables, including broccoli, corn, peas, potato skins, leafy greens, and tomatoes
  • Fruits: raw or dried fruit, mandarin oranges, pineapple, prune juice, and fruit skins
  • Grains: brown rice, cereals, popcorn, oats, and whole-grain bread, pasta, and tortillas
  • Legumes: beans, peanuts, chickpeas, green peas, and lentils
  • Nuts and seeds: almonds, chia seeds, cashews, flax seeds, pecans, walnuts, etc.

Foods to eat

Here are low-fiber foods you can eat before your colonoscopy:

  • Vegetables: cooked carrots or green beans, potatoes without the skin, and strained vegetable juice
  • Fruits: applesauce, canned peaches, fruit juice, and pears
  • Grains: cream of wheat, corn tortillas, crackers, and white bread and rice
  • Dairy: cottage cheese, milk, and yogurt
  • Protein: beef, chicken, eggs, pork, and tofu

1-day sample colonoscopy diet

Here’s a 1-day sample colonoscopy diet that contains under 10 grams of fiber:

Breakfast

  • 2 scrambled eggs
  • 1/2 cup cream of wheat (0.5 grams fiber)
  • 1 slice white toast (1 gram fiber)
  • 1 teaspoon margarine

Snack

Lunch

  • 3 oz tuna
  • 2 slices white bread (2 grams fiber)
  • 1 tablespoon mayonnaise
  • 1 cup chicken noodle soup (1 gram fiber)

Snack

  • 6 saltine crackers (0.5 grams)
  • 2 ounces cheddar cheese

Dinner

  • 4 ounces baked chicken breast
  • 1 cup white rice (0.5 grams fiber)
  • 1/2 cup cooked canned green beans (2 grams fiber)

The bottom line

A colonoscopy prep ensures that your large intestine or colon contains little residue so that the doctor can get a clear view during the procedure.

The process involves consuming a low-residue diet — which consists of less than 10 grams of fiber — the day before the procedure.

The colonoscopy process also involves drinking a laxative solution using a split-dose regimen, which entails drinking half the solution the evening before the procedure and the second half several hours before the procedure.


Gavin Van De Walle, MS, RD, LN
Gavin Van De Walle, MS, RD, LN

Gavin Van De Walle holds a master's degree in human nutrition and bioenergetics. He is a registered dietitian who aims to arm the public with evidence-based nutrition recommendations so they can make their own educated and informed health decisions.