Juice fasts have surged in popularity, fueled by promises of rapid weight loss, detoxification, and improved well-being. A juice fast typically involves consuming only fruit and vegetable juices for a set period, often ranging from 3 to 30 days. While proponents tout numerous benefits, it's crucial to understand the potential risks and limitations before embarking on a 30-day juice fast.
What is a Juice Fast?
A juice fast is a type of short-term detox diet that involves consuming only juices from fruits and vegetables. Fresh juice is made by extracting liquid from fruits and vegetables, most often with a juicing machine, but can also be done by blending the foods and squeezing the juice through a cheesecloth or strainer. These cleanses are often promoted as a way to lose weight, clear toxins from the body, and improve skin condition. However, many health claims presented with juicing and detoxing plans are not based on scientific evidence.
How Does a 30-Day Juice Fast Work?
The parameters of a 30-day juice fast can vary. Some plans recommend fruit and vegetable juices only for 30 days. Most plans suggest juices for up to one week, followed by a week of vegetable soups and smoothies, followed by raw foods, but no meats or animal foods, to gradually get your digestive tract working again.
Phases of a Typical Juice Fast
- Juice-Only Phase: This phase usually lasts for seven days and involves consuming only freshly made fruit and vegetable juices and water. Homemade juices are recommended, since commercially made juices may contain added sugars or other ingredients. Some people dilute their juice with equal parts juice and filtered water, while others drink 8 ounces (oz) of juice followed by 8 oz of water.
- Light Eating Phase: This phase typically lasts for three to seven days and involves eating low-calorie, plant-based foods like soups, salads, and smoothies. This phase is intended to allow your body to readjust to solid foods after a week of a liquid diet.
- Raw Eating Phase: In this phase, about 75 percent of your intake comes from fresh, raw foods, while the other 25 percent can come from cooked foods. Meat and poultry are usually discouraged, as are cooking methods like frying and breading.
Foods to Include and Avoid
During the juices-only phase of the fast, you can drink juices with the following ingredients:
- Apples
- Berries
- Bananas
- Citrus fruits
- Kiwi
- Pomegranate
- Pineapple
- Lemon juice
- Watermelon
- Bell peppers
- Cucumber
- Celery
- Fresh herbs
- Leafy greens like kale, spinach, and chard
- Cruciferous vegetables like broccoli, cauliflower, and Brussels sprouts
- Carrots
- Zucchini
Foods to avoid during a juice fast typically include:
Read also: Explore the pros and cons of fruit juice detoxes.
- Meats, including chicken, pork, beef, and lamb
- Dairy foods like cheese, milk, and yogurt
- Beans and legumes
- Grains like bread, pasta, rice, oats, and quinoa
- Nuts and seeds
- Added fats like cooking oils, salad dressings, and mayonnaise
- Sugar-sweetened beverages
- Alcohol
Potential Benefits of a Juice Fast
Weight Loss
By consuming only juice for a week (and very light meals for additional weeks), you’ll trim your calorie intake considerably. For this reason, weight loss is likely during a juice fast. Juice cleanses may help increase the number of healthy bacteria in your gut, which has been linked to weight loss. In a 2017 study, a 3-day juice-only diet altered the gut bacteria in 20 healthy adult participants. However, rapid weight loss isn’t usually lasting weight loss. Though a juice fast might melt away pounds quickly, it’s not a long-term solution and could lead to a cycle of yo-yo dieting.
Detoxification
Advocates of juice cleanses often claim that the programs can help remove toxins from a person’s system. An increase in fluid consumption can help kidney function, and some nutritional compounds may help in the removal of non-organic waste products in the body. However, there is insufficient evidence to suggest that juice cleanses or other detoxification diets impact the ability to remove toxins. According to the University of Rochester Medical Center, your kidneys and liver do that job 24/7, so the best way to remove toxins is to support these organs with a healthy, balanced diet high in whole fruits, vegetables, and other high-fiber foods, and low in salt and added sugars, especially in ultra-processed foods and alcohol.
Increased Nutrient Intake
Juicing makes it much easier to sneak in a few extra veggies with each meal or snack. Juicing also allows you to get adventurous with the produce you consume. Drinking juice enables the body to better absorb the vitamins, minerals, and enzymes that juice has to offer. A shriveled carrot or sad-looking cucumber might not make for an appealing addition to dinner, but either is excellent in juice cleanse recipes - and a great way to stop tossing out produce that’s a bit past its prime.
Potential Risks of a Juice Fast
Nutrient Deficiencies
Though fruits and vegetables have lots of important nutrients, they’re notably lacking in protein, fat, and certain micronutrients like vitamin B12, according to Houston Methodist. Going without these nutrients for too long could lead to deficiencies. Furthermore, as fiber is extracted from the plants being juiced, important nutrients bound to the fiber are lost. Fiber in whole, un-juiced fruit helps to pace absorption of fruit sugar. Without fiber, these sugars are absorbed into the blood more rapidly causing a spike in blood sugar, which can leave you feeling fatigued and hungry.
Elevated Blood Sugar
Fruit juice is very high in sugar, which can cause high blood sugar in someone with diabetes or prediabetes, according to Diabetes.co.uk. Pureed juice drinks contain a lot of sugar, in the form of glucose, and lack fiber. This leads to many individuals feeling hungrier than usual, as their blood sugar levels spike and then drop. Blood sugar spikes can cause brief spurts of energy followed by slumps, manifesting as 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: Juice Cleanse: Benefits and Risks
Undesirable Changes from Low Fiber
A study published in 2025 found that juice diets lacking in fiber caused harmful changes to oral and gut bacteria after just three days. Meanwhile, low fiber intake could slow down your digestion, causing constipation. 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. The high sugar content in juice further fuels these harmful bacteria, disrupting the gut and oral microbiome.
Unsustainable Weight Loss
Rapid weight loss isn’t usually lasting weight loss, according to the Mayo Clinic. Though a juice fast might melt away pounds quickly, it’s not a long-term solution and could lead to a cycle of yo-yo dieting. When you resume your usual eating habits, you’re likely to regain weight lost during a short-term fast, according to the Mayo Clinic.
Lack of Scientific Evidence
Scientific evidence doesn’t support juicing’s claim to detoxify the body or individual organs. There is a lack of scientific evidence to support the effectiveness of juice cleanses.
Social Isolation
The restrictive nature of a juice fast could mean difficulty socializing over meals. During this time, you might lose out on the pleasure of enjoying food with others.
Risks Associated with Juice Cleanses
Several risks are linked to juice cleanses, and there is little evidence to their benefits.
Read also: Renal Diet Guide: Navigating Orange Juice Consumption
- 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.
- 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.
- Malnutrition: A person on a juice cleanse may not consume enough proteins or fats. Both of these are crucial to physical health, healing, and brain function. Eliminating food groups for extended periods may also lead to malnourishment.
- 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.
- Kidney health: Some foods are 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. People living with chronic kidney disease may be at risk of oxalate nephropathy.
Increased 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.
Alternatives to Juice Fasts
Someone wishing to lose or maintain a healthy weight and support their body’s natural processes can try the following alternatives:
- 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.
Who Should Avoid Juice Fasts?
If you have a medical condition or are on prescribed medication, consult your GP before making any drastic changes to your eating patterns. The high consumption of natural sugars implicit in juicing can cause blood-sugar levels to fluctuate, so those with diabetes or blood sugar management issues should avoid juice diets.
It is also advisable to avoid juice diets if you:
- are pregnant, or breastfeeding
- are elderly, or under 18
- are recovering from surgery
- have kidney or liver conditions
- have epilepsy
- have anaemia, or low blood pressure
- have a history of eating disorders