Why clear liquid diets are so important for colonoscopies, and other times you may want to try it

• Clear liquid diets allow foods that you can see through like gelatin, broth, soda, and popsicles.
• Solid food and opaque liquids like meat, fruit, and milk are off-limits on a clear liquid diet.
• Clear liquid diets are designed to be temporary and are dangerous to follow long-term.
• Visit Insider's Health Reference library for more advice.

A clear liquid diet is often prescribed before a patient undergoes gastrointestinal procedures such as colonoscopies or endoscopies. Strictly consuming clear liquids reduces residue in the intestinal tract, which helps doctors perform the necessary medical procedure.

You may also be instructed to follow the diet to manage certain digestive disorders, such as diarrhea or vomiting, says James J. Farrell, MD, advanced endoscopy doctor at Yale Medicine and professor of medicine at the Yale School of Medicine. The diet allows your bowels to rest and heal from the discomfort.

The clear liquid diet does not provide adequate calories and nutrients and it should not be followed for more than five days. Otherwise, it may pose risks to your health.

Here's what you can eat on a clear liquid diet and why you shouldn't follow it for a prolonged period.

What can you eat on a clear liquid diet?

No solid foods of any kind are allowed while on the clear liquid diet. "If you can see through the 'liquid,' it is probably safe to follow, such as tea or gelatin. Even solids which melt into clear liquids may be acceptable, like hard candy or ice pops," says Farrell.

Here is a guide on what you can and cannot eat on a clear liquid diet:

Food group	Foods allowed	Foods not allowed
Fruits & vegetables	None	All of it
Meat	None	All of it
Grains	None	All of it
Soups	Clear, fat-free broth or bouillon	Cream soups Noodle soups
Beverages	Water Coffee or tea with no added milk or cream Strained clear fruit juices without pulp such as apple juice or lemonade Clear sodas like ginger ale or Sprite Carbonated drinks like cola or root beer Sports drinks like Gatorade	Milk and milk alternatives Cream Juice with nectar or pulp such as orange juice
Other	Popsicles or ice drops without solid fruit Hard candies like lemon drops or lollipops Plain gelatin without fruit or whipped cream	Any gelatin, popsicles, or ice drops with fruit or toppings Chocolate Ice cream Yogurt and sherbets

In some instances, the doctor will make adjustments on what you cannot eat, depending on the medical procedure. For instance, you are required to avoid food and drinks with red or purple food coloring for colonoscopies because it can be confused with blood, says Farrell.

A clear liquid diet might make you feel hungry or tired because it doesn't provide you with the necessary calories and nutrients, so take it easy and avoid extreme physical activity. To feel full, drink plenty of water and eat frequently throughout the day.

Health risks of a clear liquid diet

Because the clear liquid diet restricts the consumption of solid foods and has limited nutritional value, you may suffer from malnutrition if you follow it for an extended period or without medical supervision. Malnutrition can affect the function of every organ system in the body. Its initial symptoms include fatigue and weakness.

People with diabetes should monitor their blood sugar more frequently when following a clear liquid diet, says Farrell, because they have an increased risk of developing hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar). If you have diabetes, consult your primary care provider about any necessary adjustments to your insulin doses.

"If a clear liquid diet is medically necessary, individuals with [previous or present] eating disorders should discuss their eating disorder with their provider and have the support of family and a therapist or psychologist to prevent a relapse," says Janet Lydecker, PhD, psychologist and eating disorder expert at the Yale School of Medicine. Otherwise, they may begin to over-restrict their eating after it is no longer necessary.

Be sure to follow the diet closely before your medical procedure because your incomplete bowel preparation can result in an inaccurate examination, says Farrell.

Insider's takeaway

Related Article Module: 6 easy-to-digest foods for when you have stomach issues

You may be required to follow a clear liquid diet if you have certain digestive disorders or you're about to undergo gastrointestinal procedures such as colonoscopies or endoscopies. On this diet, you can only consume see-through liquids that don't contain bits of solid foods.

Failing to follow a clear liquid diet can result in an inaccurate test and require you to reschedule the procedure for another time. Refrain from following the diet longer than the doctor ordered, otherwise, you may experience malnutrition.

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