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Liquid Diet- What you need to know

Updated on September 28, 2021
Medically Reviewed by
Dr. Dhingra
Written by
Ada Sandoval
5 sources cited
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Liquid diets such as fruit smoothies, soups, and stews are usually supplements to regular diets. But in recent years, the liquid diet has proven to serve more purpose than just a sidekick to standard meals.

A full liquid diet includes fluids, soluble fibers, and other additives. There are many reasons why people resort to liquid diets. Some take liquid diets to lose weight, while others take them after surgery to sustain feeding until swallowing is possible.

Some people may also be prescribed a liquid diet if they have gut problems like gastroparesis or the inability to digest solid food. In these cases, a registered dietitian or doctor may recommend shifting to a liquid diet as a temporary source of nutrition. Patients are advised to revert to solid food as soon as they recover.

When do doctors and dietitians recommend liquid diets?

Doctors and dietitians usually recommend a liquid diet plan when a patient is unable to digest or swallow solid foods. Liquid diets are easy to prepare and eat. They are usually light and easily digestible for patients with gut problems.

A doctor may recommend a liquid diet plan in the following conditions:

  • After undergoing dental or oral surgery
  • Before and after pancreatic surgery
  • Recovering from mouth or jaw injuries which may prevent chewing
  • Before a colonoscopy
  • Teeth loss from injuries or infection
  • Mild gastroparesis

Recently, dietitians have started to recommend liquid diets for weight loss. Early studies support this that consuming liquid diets prevents the patient from consuming too many calories.1

Research also suggests that if you eat a low-calorie liquid diet, this can aid in weight loss. Based on evidence, replacing solid foods with a liquids  tricks the stomach into thinking that it is fuller than it actually is. This prevents overeating and helps you keep your weight in check.

However, scientists are conflicted. Others say this method of weight loss isn’t sustainable because most people regain the lost weight weeks after reverting to their usual diet.

What is a liquid diet?

A liquid diet can consist of pure liquid foods – such as juice and tea. But it may also contain solid foods that turn into liquid at room temperature – like ice cream and popsicles.

Types of liquid diets: Full vs. clear liquid diet

Liquid diets are divided into two types:

  • The full liquid diet
  • The clear liquid diet

The full liquid diet

A full liquid diet consists of all types of liquids. This includes smooth liquids that are either transparent or opaque, solid foods that have been liquefied or blended, and foods that have been blended with other liquids. Full liquid diets are mostly made of liquid. However, they are supplemented with some fibers, smooth cereals, and creams. 

What you need to know about a full liquid diet

It is not the same as a soft diet which is a combination of clear liquid and full liquid diets, along with some semi-solid foods. For people who are unable to chew or digest food properly, a full liquid diet is nutritionally the closest thing to eating solid food. 

Unlike a clear liquid diet, it is packed with vitamins and minerals. This makes it the middle ground between solid foods and clear liquids in terms of nutrition. In fact, a full liquid diet should continue to provide adults with the average daily intake of 2,000 cal and 70 g of protein.2

One important feature of a full liquid diet is that it’s much thicker in consistency than clear liquids. Below are some foods and food groups that can be included in this diet:3

  • Milk and dairy products – Milkshake, protein shake, plain yogurt (without nuts, seeds, or any solid food material), and whipped cream or any whipped toppings
  • Meat and meat substitutes – Eggnog and custard
  • Breads and grains – Smooth cereals, oatmeal, and cream of wheat
  • Fruits and vegetables – Strained juices or smoothies made of citrus fruits, carrots, and tomato
  • Desserts and sweets – Pudding, plain gelatin and ice cream (with no solids), syrup, sherbets, sorbets, frozen yogurt, hard candies, sugar, honey, and popsicles
  • Drinks – Coffee, tea, hot beverages soft drinks, lemonades, and limeades.
  • Other foods that can be blended into liquid – Margarine, butter, cream, and non-dairy creamer

Full liquid diets are more flavorful and nutritious than a clear liquid diet. However, full liquid diets do not contain enough protein or fiber when compared to a normal diet.

If you're planning to eat a full liquid diet for a long time (say a few weeks), stick to foods with enough protein and a considerable amount of nutrients.

Some of these foods include:

  • Protein drinks (with less sugar as possible)
  • Dairy (lactose-intolerant people should consider nut and seed milk)
  • Pureed eggs, meat, and beans
  • Gravy with mashed sweet or Irish potatoes – can contain pureed meat

A full liquid diet should only be considered during recovery from a medical condition. When you're well enough to take solid food again, you should certainly go back to them. Just remember to consult your doctor or dietitian if you have any questions about your diet.

A registered dietitian can create a specialized diet plan based on your health information and nutritional needs. They can calculate calories according to your weight, and suggest foods to include and exclude from your diet.

The clear liquid diet

A clear liquid diet consists only of liquids that are transparent at room temperature. It should have little to no visible residue, which you would normally observe in smoothed solids and opaque liquids. This form of liquid diet is easily digested, so it quickly empties from your stomach.

Purpose of the clear liquid diet

Doctors may recommend a clear liquid diet for patients who shouldn’t have any food in their stomach or intestines during a test or diagnostic procedure, such as a colonoscopy, or after a gastrointestinal surgery. They’re also prescribed for people with digestive problems like diarrhea. 

Most clear liquid diets are transparent or translucent. They also melt or thaw at room temperature. Doctors advise patients not to consume any solid food while on a clear liquid diet.

Clear liquid diet guidelines

A clear liquid diet provides the minimum required fluids and calories. It’s meant to keep a person hydrated and energized, until such time when they’re allowed to eat a normal diet or shift to a more nutritious one.

Clear liquid diets that are prepared by a registered dietitian provide about 600 cal and 150 g carbohydrate. However, they tend to lack protein, vitamins, and minerals.2 

Since clear liquids can't provide your required daily calories, doctors and dietitians don’t recommend them for more than 3 days. If necessary, they will prescribe supplements to ensure you’re getting enough nutrients.

Most clear liquid diet plans consist of the following foods and food groups:3

  • Fruits and vegetables – Clear, strained, or pulp-free juices and fruit ices made of apple, orange, cranberry, lemons, and grapefruit
  • Desserts and sweets – Popsicle, clear flavored gelatin and fruit ices, hard candy, and honey
  • Beverages – Sports drinks, clear coffee or tea, and carbonated beverages
  • Other clear liquids – Broth or bouillon

The clear liquid diet might not be appealing in terms of taste. However, it reduces stress on the digestive system while keeping the body hydrated and functional.

The Pros and Cons of Liquid Diets vs. Solid Foods

 Doctors and dietitians recommend liquid diets for many reasons. But there are also drawbacks associated with its consumption.

The pros of a liquid diet

  1. It helps with weight loss

For people who are trying to lose weight, one reported benefit of liquid diets is that they can help with weight loss. High-calorie intake is one of the main factors that contribute to weight gain. Replacing solid foods with liquids effectively curbs hunger and reduces a person’s overall calorie intake.4 

  1. It’s convenient

Liquid diets are more convenient because they’re easier to prepare and consume. Unlike solid foods which have an average cooking time of 30 minutes, liquids can be prepared in as little as 10 minutes which helps you save time.

  1. It can remove toxins

Liquid diets give the body time to rest and sort itself out. Since there aren’t too many calories to digest, the body can use this time to get rid of harmful toxins and oxidants that may have accumulated in its system.

  1. It's economic

Liquid diets are pretty affordable. They usually contain a  combination of readily available food materials which you can buy at the grocery store or farmer’s market.

5. It’s packed with nutrients

With the right choice of ingredients and good recipes, a full liquid diet can be beneficial for your health. You can create nutrient-dense smoothies and juices that are rich in protein or certain vitamins.

The cons of a liquid diet

  1. It causes an imbalanced diet

Liquid diets limit the types of food you can add to your meals. While this can help you get certain nutrients, you also miss out on vitamins and minerals found in solid foods. For example, full liquid diets tend to be loaded with calcium and vitamins A and C, but are missing other essential nutrients. Clear liquid diets are not only missing nutrients but calories as well. 

Liquid diets  deprive the body of much-needed nutrition required for overall function, especially when eaten for prolonged periods. 

  1. Inadequate digestion

Most liquid diets are not properly digested because they bypass some digestive functions, such as the mouth. The digestion of foods like carbohydrates begins in the mouth. If it is bypassed, the body is unable to utilize all of the nutrients found in food, which leads to poor nutrition.

  1. Nutritional deficiencies

Since most liquid diets don't contain enough vitamins and minerals, this can lead to nutrient deficiencies. Lack of vitamins and minerals in the body can result in health conditions such as scurvy, osteomalacia, and night blindness.

Potential Benefits of an All Liquid Diet

Liquid diets offer different benefits for the patient, the physician, and the registered dietitian. Below are the possible benefits of an all-liquid diet.

  1. Prevent complications

An all-liquid diet can reduce pain and minimize injury in patients suffering or recovering from certain conditions. For example, people with broken jaws, incisions caused by broken teeth, and those who underwent dental surgeries can be protected from pain and injury if they eat liquid diets. 

Liquid diets also help the patient avoid solid food debris from entering surgical wounds and causing infections.

  1. Error-free tests and accurate diagnosis

A clear liquid diet is usually recommended before colonoscopy. This is to allow doctors to clearly see any abnormal growths in the intestinal wall during the process. 

A liquid diet makes it possible for the patient to have some food in their gut; while also allowing the doctor to see the colon a lot clearer during diagnosis.

  1. Easier digestion

Liquid diets are easily absorbed in the stomach and intestines. This is because it's easier for liquids to empty from the stomach than solid food. When digesting liquid diets, the stomach usually requires less time and energy to absorb nutrients and use them for bodily functions.

Potential Risks Associated with Liquid Diets

Doctors and dietitians recommend liquid diets as a short-term alternative, lasting no more than a few days. After the procedure, you need to resume your normal diet. If you continue to eat liquids against your doctor’s prescription, you may be at risk for the following:

  1. Unhealthy weight loss

Liquid diets can be beneficial to those that want to shed some weight. However, it isn’t good for individuals who need to maintain their normal weight, or have already lost significant weight. 

A normal healthy diet for adults aged 19 to 30 years should consist of at least 2,000 to 2,400 calories.5 Liquid diets – especially clear liquids – provide much less than that. If you don’t get enough calories, it may cause you to lose weight. Talk to your doctor or a registered dietitian if you are already underweight so that you can discuss alternatives.

  1. Poor health

People who take an all liquid diet for prolonged periods risk calorie deficiency and poor health. Calories are an important aspect of nutrition. And if a person doesn't get enough, their normal bodily functions also get affected. 

A calorie deficiency may result in fatigue, hair loss, dizziness, electrolyte imbalance, muscle loss, and in some severe cases, heart diseases.

  1. Changes in gut health

Liquid diets may contain some soluble fibers, but they lack insoluble fibers or bulk which are more important. Insoluble fibers facilitate the digestion of food and play a significant role in gut health. Depriving the gut of these fibers (as seen in liquid diets) will disrupt the healthy process of your gut flora and lead to abnormal changes.

Things to Consider Before Choosing an All Liquid Diet Plan

It would be careless to switch to a liquid diet without consulting your doctor or a registered dietitian. These health professionals can properly assess your current physical health to see if you're fit for full or clear liquids.

Before they recommend and plan a liquid diet plan, they may check for the presence of the following health conditions:

  • Pregnancy
  • Age
  • Weight
  • Pre-existing conditions such as diabetes, gastrointestinal disorders, and cancer
  • Recurrent fever, nausea, and vomiting
  • Food allergies and other food hypersensitivities
  • Kidney diseases
  • Heart disease
  • Daily calorie intake

 After checking for these factors, they can decide whether to put you on a full liquid or clear liquid diet. A registered dietitian can also calculate your required caloric intake based on your health, age, and weight – and plan your meals. 

How to Get Started with a Liquid Diet Plan

Starting a liquid diet may need the professional guidance of a dietitian. Your dietitian will create a meal plan and include foods that are safe, nutritious, and allowable. You have to strictly follow this diet plan to ensure adequate nutrition and avoid potential risks. 

Below is a sample of what a typical liquid diet meal plan may look like:

Breakfast

  • 1 glass pulp-free fruit juice
  • 1 bowl jello
  • 1 cup of coffee or tea, without dairy products
  • Sugar or honey, if desired

Snack

  • 1 glass fruit juice (pulp-free)
  • 1 bowl jello

Lunch

  • 1 glass pulp-free fruit juice
  • 1 glass water
  • 1 cup broth
  • 1 bowl jello

Snack

  • 1 pulp-free ice pop
  • 1 cup coffee or tea, without dairy products, or a soft drink
  • Sugar or honey if desired.

Dinner

  • 1 cup pulp-free juice or water
  • 1 cup broth
  • 1 bowl jello
  • 1 cup coffee or tea, without dairy products
  • Sugar or honey, if desired. (Source: Mayoclinic)

Take note that the above diet plan is just an example. Your doctor or dietitian will likely recommend a liquid diet that is suited to your needs. Before starting your liquid diet, make sure to ask your doctor any questions you may have, such as which foods are not allowed and what to expect while on the diet.

Resources

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(1) “Doctor Referral of Overweight People to Low Energy total diet replacement Treatment (DROPLET): pragmatic randomised controlled trial.” British Medical Journal.

(2) “Nutrition, Malnutrition, and Probiotics.” ScienceDirect.

(3) “Diets.” ScienceDirect.

(4) “Meal Replacement Beverage Twice a Day in Overweight and Obese Adults.” National Center for Biotechnology Information.

(5) “Dietary Guidelines for Americans: 2015-2020, Eighth Edition.” United States Department of Agriculture.

Dr. Dhingra
Dr. Harshi Dhingra
Medical Reviewer
Dr Harshi Dhingra is a licensed medical doctor with a specialization in Pathology. Dr. Dhingra has of over a decade in diagnostic, clinical, research and teaching work, including managing all sections of Pathology laboratory including histopathology, cytology, hematology and clinical Pathology.
Ada Sandoval
Content Contributor
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