Juice fasting, a dietary regimen consisting entirely of fruit and vegetable juices, has gained popularity as a quick way to lose weight, "detox," and improve overall health. Typically lasting for 3-10 days, these fasts involve extracting juice from fruits and vegetables while discarding the pulp and skin. While proponents claim various benefits, it's crucial to understand both the potential advantages and the risks associated with this practice.
What is a Juice Fast?
Juicing involves extracting juice from fruits and vegetables, often through pressing or squeezing, while discarding the pulp and skin. This process differs from blending, where the entire fruit or vegetable, including the fiber, is consumed. Juice cleanses typically involve consuming only fruit and vegetable juices for a specified period, ranging from three to ten days, while abstaining from solid foods.
Potential Benefits of Juice Fasting
While claims surrounding juice fasting are often overstated and lack robust scientific backing, some potential benefits may exist:
Increased Nutrient Intake
Fruits and vegetables are rich in vitamins, minerals, trace elements, enzymes, and natural sugars. Juicing may increase the bioavailability of certain nutrients, such as vitamin C, flavonoids, and other beneficial phytochemicals. Studies have shown that consuming blended drinks leads to a higher availability of antioxidants and other active chemicals in plant foods.
Gut Health
Some research suggests that juice cleanses may alter gut bacteria, potentially increasing beneficial bacteria linked to weight loss. However, other studies have found limited effects on gut bacteria composition.
Read also: 7-Day Juice Cleanse
Short-Term Weight Loss
Juice cleanses may lead to initial weight loss due to calorie restriction. However, this weight loss is often unsustainable and primarily consists of water weight.
Kidney Function
Increased fluid consumption from juices can support kidney function, and certain nutritional compounds may aid in removing non-organic waste products from the body.
Risks and Drawbacks of Juice Fasting
Despite potential benefits, juice fasting carries several risks that should be carefully considered:
Nutritional Deficiencies
Juice fasts are often very low in calories and may only include 150-300 calories daily. Juice fasting does not provide proper nutrition and can cause a person to develop nutritional deficiencies. They typically lack essential nutrients like protein, fat, and vitamin B12. This can lead to malnutrition and associated health problems.
High Sugar Intake
Pureed juice drinks contain a lot of sugar, in the form of glucose, and lack fiber. Fruit juice is very high in sugar, which can cause high blood sugar in someone with diabetes or prediabetes. This can lead to blood sugar spikes, followed by energy slumps, tiredness, headaches, and irritability. High blood sugar levels lead to stiffening of the red cell membrane, which hinders their passage through the body, increasing cholesterol deposits in the blood.
Read also: Explore the pros and cons of fruit juice detoxes.
Loss of Muscle Mass
Lack of protein leads to the person not feeling full, creating a psychological pressure to eat more. In addition to the temptation to eat something rich and filling, there is also a loss of muscle mass due to the protein deficit, which means that after the diet the weight is regained.
Negative Impact on Gut Microbiome
A study published in 2025 found that juice diets lacking in fiber caused harmful changes to oral and gut bacteria after just three days. Juicing strips away much of the fiber in whole fruits and vegetables, which feeds beneficial bacteria that produce anti-inflammatory compounds such as butyrate. Without fiber, sugar-loving bacteria can multiply.
Kidney Problems
Juice fasting has caused kidney problems in healthy people. Some foods high in oxalate, a compound that can increase a person’s risk of kidney problems when consumed in high quantities. Foods high in oxalate include spinach and beets.
Unsustainable Weight Loss
Severe caloric restriction is not sustainable for most people and rarely leads to long-term weight loss. It may also increase a person’s risk of other complications. In most cases, a person will return to their starting weight quickly once caloric restriction ends. Rapid weight loss isn’t usually lasting weight loss, according to the Mayo Clinic.
Low Blood Sugar
Consuming an insufficient number of calories can cause a person to experience symptoms relating to low blood sugar, including fainting, weakness, dehydration, headaches, and hunger.
Read also: Juice Cleanse: Benefits and Risks
Dehydration
If a juice cleanse includes laxatives or other methods of bowel stimulation, a person could lose too many nutrients in their stool. This can lead to dehydration and imbalanced electrolytes.
Increased Risk of Eating Disorders
Juicing may increase the risk of eating disorders. For example, an obsessive preoccupation with health-promoting foods and an avoidance of foods considered “less healthy” can lead to orthorexia nervosa.
The 21-Day Juice Fast
The 21-day juice fast is an extended version of the typical juice cleanse, often involving three phases:
- Phase 1: A week of consuming only freshly made fruit and vegetable juices and water.
- Phase 2: Several days of "light" eating, including low-calorie, plant-based foods like soups, salads, and smoothies.
- Phase 3: A "raw" eating phase where about 75% of intake comes from fresh, raw foods, with the remaining 25% from cooked foods.
While proponents claim enhanced benefits, the extended duration of this fast amplifies the risks mentioned above, making it even more crucial to proceed with caution and under medical supervision.
Alternatives to Juice Fasting
For those seeking to improve their health and well-being, several alternatives to juice fasting offer more sustainable and balanced approaches:
Balanced Diet
Eating a balanced diet and staying adequately hydrated are the best ways to maintain a healthy weight and support the body’s removal of toxins.
Plant-Based Diets
Based on minimally processed foods, these diets are naturally rich in fruit and vegetables and are associated with reduced body weight. With good planning, a plant-based diet can provide all the nutrients necessary for good health.
Intermittent Fasting
This involves abstaining from eating for limited periods and eating a regular diet at other times. Reviews have linked intermittent fasting with weight loss and improvements in insulin sensitivity.