You may need to follow a liquid diet before or after a medical test or procedure. And while getting enough protein through liquids alone can be challenging, there are still fluids high in protein to sip on. Here are the two types of liquid diets and high-protein liquids you can include in each.
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What Is a High-Protein Full Liquid Diet?
A liquid diet includes fluids and liquid foods (or foods that become liquid when they melt), according to the U.S. National Library of Medicine (NLM).
These diets are typically only followed in the days or weeks before a medical test or surgery to prepare or cleanse your body for the procedure, per University of Florida Health. You may also have to follow a liquid diet after certain procedures — namely, weight-loss surgery — to supply you with enough nutrients while you heal.
Though you're limited to eating fluids, it's still possible to get enough protein, according to the NLM. Per the 2020-2025 Dietary Guidelines for Americans, adults should aim to eat the following amount of protein per day:
- People assigned female at birth: 46 g
- People assigned male at birth: 56 g
However, full liquid diets don't supply you with enough other important nutrients like fiber, per the NLM, so it's important to only try these diets under your doctor's order and supervision.
Best Liquid Protein Diet for Weight-Loss Surgery
You may be asked to follow a liquid diet starting about two weeks before surgery, which often includes drinking multiple protein shakes per day and supplementing your meals with a multivitamin, according to University of Florida Health. Your doctor may also advise you to stick to low-carb liquid protein shakes.
After your procedure, you'll typically slowly eat six small meals per day until you recover, per the University of Rochester Medical Center. You should also drink plenty of fluid before and after surgery to stay well-hydrated.
When it comes to the specifics of your surgical meal plan, follow your doctor's instructions for exactly which foods to eat and avoid.
Foods to Eat
You can eat any liquid foods or drinks on this diet, according to the NLM. Per the University of Rochester, the best way to get protein is to sip fluids high in the nutrient, like:
- Broth with protein powder
- Cream-based soups
- Milk or dairy-free alternatives like soy milk
- Greek yogurt
- Nutritional drinks like Boost or Ensure
- Protein shakes with milk, yogurt, protein powder and/or a sweetener like jelly
Other foods to eat on a full liquid diet include:
- Sour cream
- Ice pops
- Smoothies without any chunks
Foods to Avoid
Per the NLM, there are some foods to look out for that may seem like they fit into a liquid diet, but don't, such as:
- Mashed or pureed fruits and vegetables, like mashed potato or avocado
- Ice cream with chunks or toppings
- Strained meats, like those in baby food
What Is a High-Protein Clear Liquid Diet?
A clear liquid diet only permits foods and drinks that are see-through at room temperature, per the Mayo Clinic. This type of diet is typically recommended before a procedure like a colonoscopy, where it's important that your digestive tract is free of food residue so your doctor has an unobstructed view of your colon and can detect any problems.
Foods to Eat
According to Harvard Health Publishing, what you can eat on a clear liquid diet is limited to see-through fluids such as:
- Pulp-free juice like white grape or apple juice
- Electrolyte sports drinks
- Clear sodas like ginger ale
- Tea or coffee (without milk or cream)
- Ice pops or fruit ice
- Clear hard candy like lemon drops
- Fruit-flavored gelatin or Jell-O
Eating a high-protein clear liquid diet can be more challenging given these restrictions. Foods that provide clear liquid protein include:
- Clear soups and broths like vegetable, beef and chicken broth or bouillon
- Clear liquid protein drinks like Ensure Clear, per UVA Health
Foods to Avoid
Skip any fluids you can't see through, per the Colorectal Cancer Alliance. That includes avoiding these liquid proteins:
- Milk and other dairy products
- Coffee or tea with milk added
- Cream-based soups
- Anything pureed that is cloudy or creamy
- Cloudy stock, miso soup and bone broth (with or without protein powder)
Clear liquid diets are meant for short-term, medical use only. They don't provide enough essential nutrients, so you should only follow a doctor-prescribed liquid diet in preparation for a medical test or procedure, per the Mayo Clinic.
- U.S. National Library of Medicine: "Full liquid diet"
- U.S. Department of Agriculture and U.S. Department of Health and Human Services: "2020-2025 Dietary Guidelines for Americans"
- University of Rochester Medical Center: "High Protein Liquid Meal Plan"
- University of Florida Health: "Liquid Diet Before Bariatric Surgery"
- Mayo Clinic: "Clear liquid diet"
- Colorectal Cancer Alliance: "How to prepare for your colonoscopy"
- Harvard Health Publishing: "Preparing for a colonoscopy"
- UVA Health: "Instructions for the Patient with Diabetes undergoing Colonoscopy"