Green juice has become a popular health and wellness trend, with celebrities, social media influencers, and wellness bloggers promoting its purported health benefits, including improved digestion, weight loss, reduced inflammation, and boosted immunity. But are these claims too good to be true? This article reviews everything you need to know about green juice, including the benefits and risks, so you can determine whether to add it to your routine.
What is Green Juice?
Green juice is a beverage made from the juices of green vegetables. There’s no official recipe, but common ingredients include celery, kale, Swiss chard, spinach, wheatgrass, cucumber, parsley, and mint. Given that green juice tends to taste bitter, most recipes add small quantities of fruit - which may or may not be green - to sweeten it and improve its overall palatability. Popular fruit options include apples, berries, kiwi, lemons, oranges, and grapefruit. The most dedicated green juice drinkers prefer fresh, homemade juice, but you can buy it from specialty juice cafés too. Commercial green juices are available as well, but some varieties contain added sugar, which reduces the drink’s nutrient density. Excess sugar intake is also linked to several adverse health effects. Moreover, many bottled green juices are pasteurized. This process heats the juice to kill harmful bacteria and extend shelf life, but it may damage some of the heat-sensitive nutrients and plant compounds found in fresh juice.
Potential Benefits of Green Juice
Green juice is not a substitute for a balanced and healthy diet, but it shares many of the benefits that come along with eating more fruits and vegetables. Green veggies and their juices are excellent sources of several essential vitamins, minerals, and beneficial plant compounds. For example, Swiss chard and kale are packed with vitamins A and K, while wheatgrass supplies plenty of vitamin C and iron. Research suggests that eating leafy green vegetables daily may help reduce inflammation, heart disease risk, and your risk of age-related mental decline. There’s also evidence that certain compounds in fresh juice can function as prebiotics, which feed and support the growth of beneficial bacteria living in your digestive tract. Routine prebiotic intake is linked to numerous benefits, including reduced constipation, weight maintenance, and improved immune function. Moreover, many people find that drinking their vegetables and fruits is an easy and efficient way to boost their intake of valuable nutrients. Finally, certain people, such as those who’ve had surgery on the stomach or intestines, can benefit from green juice, as it’s easier to digest. For these populations, juicing is a short-term option during recovery. Speak to your healthcare provider or dietitian about juicing for your specific condition.
Risks and Downsides of Green Juice
Although drinking green juice is a great way to increase your intake of a variety of important nutrients, there are several drawbacks you should consider before buying into the trend.
Low in Fiber
Juicing a fruit or vegetable removes the majority of its fiber. Fiber is vital to a healthy diet. Adequate fiber intake supports heart health by helping manage blood pressure, blood sugar, and cholesterol levels. It may also relieve certain digestive disorders, such as acid reflux, diverticulitis, and intestinal ulcers. The Institute of Medicine recommends a daily intake of 25 grams for women and 38 grams for men. Given that green juice doesn’t contain much fiber, it shouldn’t be used to substitute your veggie or fruit intake. If you’re considering adding green juice to your wellness regimen, don’t forget to eat plenty of whole vegetables and fruits as well.
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May Raise Blood Sugar
If you have diabetes or another medical condition that contributes to poor blood sugar control, juices may not be the best option for you. These drinks tend to be low in fiber and protein, two nutrients that support balanced blood sugar. Green juices made only with veggies are lower in carbs and unlikely to negatively affect your blood sugar. However, if you prefer your green juice with fruit, the sugars in the fruit may contribute to unwanted increases in your blood sugar levels. You can mitigate this effect by pairing your juice with a meal or snack that provides fiber and protein, such as flax crackers with cheese, veggie sticks with tuna salad, or oatmeal with unsweetened plant milk and almond butter. That said, you should be especially wary of store-bought green juices, as these may pack added sugar. Check the label and ensure that fruits or veggies are the only ingredients. You can also check the nutrition label for added sugar, which should be zero. This is distinct from “total sugars,” which will account for the natural sugar found in fruits.
May Harm Your Kidneys
Drinking green juice in moderation can boost your intake of multiple nutrients, but too much may cause serious side effects. Green vegetables are a rich source of oxalic acid, or oxalate, which is considered an antinutrient because it binds to minerals in food and stops your digestive tract from absorbing them. The amount of oxalates you typically consume from whole vegetables in a balanced diet isn’t harmful. However, green juices tend to be highly concentrated sources of oxalate. Too many oxalates can lead to negative health effects, including kidney stones and even kidney failure. A handful of recent cases of acute kidney failure have been attributed to excess oxalate intake from green juices and smoothies included in cleanse or fasting protocols. Although juice cleanses, detoxes, and fasts are a popular trend, relying on green juice - or any other juice - as a sole source of nutrition is never necessary and may harm your health. If you plan on including green juice in your diet, play it safe by practicing moderation and eating balanced meals that include a variety of whole foods. "Anyone with kidney disease should not undergo a juice cleanse," warns Beaver.
Juice Cleanses: An Overview
A juice cleanse is a diet that involves consuming only juices from vegetables and fruits. Advocates claim that juice cleanses can help remove toxins from the body and aid in weight loss. However, there is insufficient evidence to support the benefit of juice-based diets. Research has linked liquid diets with an increased risk of serious health complications and eating disorders.
Potential Risks of Juice Cleanses
- 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. "Not only is rapid weight loss unhealthy, but it doesn't last," says Beaver. Beaver says that the weight loss you may see is mostly due to the lack of food in your GI tract and the loss of muscle experienced during a juice cleanse.
- 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.
A person should also be wary of pre-packaged juice cleanses that promise significant results, such as reversing diseases or providing dramatic health benefits. There is usually a lack of research to support these claims.
Impact on Kidney Health
Many fruits and vegetables are rich in nutrients that can assist in the good working of the kidneys. Increasing fluid consumption can also be beneficial for kidney function. However, 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. In rare cases, healthy people may also be at risk of this. Oxalate nephropathy is a condition in which the body cannot excrete enough oxalate through urine, causing it to build up in kidney tissue. In rare cases, this can cause kidney failure.
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Weight Loss and Gut Bacteria
Proponents of juice cleanses claim that it can aid weight loss. However, a 2017 review found that while juice cleanses may cause initial weight loss due to calorie restriction, they will lead to overall weight gain once a person resumes a full, healthful diet. Studies also show that weight loss from juice-based diets may be “physiologically harmful” to participants. Researchers have also observed links between liquid diet trends and eating disorders. Proponents claim that juice cleanses can alter a person’s gut bacteria. However, research shows that juice-only diets have a limited effect on gut bacteria composition.
Detoxification Claims
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. "The science of detoxifying is still being researched, so don't fall for the marketing ploys that juice cleansing companies are trying to sell you," says Beaver.
Alternatives to Juice Cleanses
A person should only adhere to juice cleanses or restricted liquid diets under medical supervision. There is insufficient evidence to assess the efficacy of juice cleanses. 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.
Juice cleanses are controversial in the medical community because they do not usually offer long-term weight loss or wellness solutions. Most experts will recommend a balanced, healthful diet instead.
The 21-Day Juice Fast: A Closer Look
Look online and you’ll find a variety of guidelines for a 21-day juice fast. “Some 21-day plans (usually those promoted by juice companies) recommend fruit and vegetable juices only for 21 days,” says Scottsdale, Arizona’s Anne Danahy, MS, RDN, of Craving Something Healthy. “However, 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.” People may choose to adopt a 21-day juice fast for different reasons. For many, it’s a tool for weight loss, since consuming only juice (and raw, light foods in later phases of the diet) cuts calories down significantly. For others, a 21-day juice fast is intended to “detox” the body of heavy metals and other harmful substances. Still others use a 21-day juice fast as part of a spiritual practice, seeking the mental clarity that may come from fasting.
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What Can You Eat on the 21-Day Juice Fast Diet?
Again, the parameters of a 21-day juice fast are quite variable. It’s largely up to you to determine what you will eat at different phases of the diet. That said, many plans involve the following:
- A seven-day phase of 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. Others drink 8 ounces (oz) of juice followed by 8 oz of water.
- A second phase of “light” eating: This often involves three to seven days of eating low-calorie, plant-based foods like soups, salads, and smoothies. Phase two is intended to allow your body to readjust to solid foods after a week of a liquid diet.
- A third phase of “raw” eating in which about 75 percent of your intake comes from fresh, raw foods: 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:
- 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 the 21-Day Juice Fast Diet (and Why They May Not Last)
By consuming only juice for a week (and very light meals for two additional weeks), you’ll trim your calorie intake considerably. For this reason, weight loss is likely during a 21-day juice fast, according to Houston Methodist. However, Danahy cautions that juice fasting isn’t a healthy or sustainable path to long-term weight loss. “Fruit and vegetable juices have virtually no protein, and are very low in calories. While that can promote weight loss, it’s mainly because you’re losing water and muscle,” Danahy says. When you resume your usual eating habits, you’re likely to regain weight lost during a short-term fast, according to the Mayo Clinic. Danahy says that the claim that a three-week juice fast will “detox” your body also doesn’t hold water. “There is no scientific evidence that a juice diet helps you detox,” Danahy says. 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. As for the mental and spiritual clarity purported to come from fasting, more scientific evidence is needed. In a small study published in 2023, men who did a water-only fast for eight days experienced no changes to their mental well-being. However, another - older - small study looked at 52 young women who fasted for 18 hours. The women reported a variety of emotional impacts, from elevated positive feelings of achievement, reward, pride, and control to increased irritability. While neither of these fasts looked specifically at 21-day juice fasts, they suggest that each person will have a unique mental, emotional, and spiritual response to fasting.
Risks of the 21-Day Juice Fast Diet
Going on a 21-day juice fast isn’t without risks. Keep these in mind when considering this fad diet.
- 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.
- 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.
- 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.
- 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.
- Lack of Scientific Evidence: Scientific evidence doesn’t support juicing’s claim to detoxify the body or individual organs.
- Social Isolation: The restrictive nature of a 21-day juice fast could mean three weeks of difficulty socializing over meals. During this time, you might lose out on the pleasure of enjoying food with others.