What Really Happens to Your Body on a Juice Cleanse
Explore the science, claims, risks, and real effects of juice cleanses, from detox myths to lasting health impacts.
Juice cleanses continue to capture curiosity and headlines as a supposed reset for our health, promising rapid detoxification, effortless weight loss, and glowing skin through the exclusive consumption of fruit and vegetable juices. But what really happens inside your body during a juice cleanse? Does the science support the claims, or do these restrictive regimens do more harm than good?
What Is a Juice Cleanse?
A juice cleanse is a diet plan that involves consuming only blended or pressed fruit and vegetable juices for a set period—commonly ranging from one to several days. Proponents claim this regimen sweeps toxins from the body, promotes weight loss, and delivers a broad array of essential nutrients. Typically, all solid food is restricted, and typical meals are replaced by several servings of juice per day.
Why Are Juice Cleanses So Popular?
The appeal of juice cleanses rests on a combination of celebrity endorsements, social media testimonials, and the modern urge for quick-fix results. Supporters assert that cleanses can:
- “Detoxify” the body by flushing out harmful substances
- Jumpstart weight loss, especially after periods of overeating
- Boost energy and mental clarity
- Enhance skin health for a radiant complexion
- Support digestion and rest the gastrointestinal system
But how do these claims align with the scientific understanding of human physiology?
The Science: How the Body Really Detoxifies
Numerous experts agree that the concept of detoxification through juice cleanses lacks scientific foundation. The human body is equipped with impressive detoxification machinery—most notably, the liver and kidneys—which handle the breakdown and removal of toxins on a continuous basis. As one registered dietitian explains, “If our bodies truly accumulated dangerous toxins day to day, we couldn’t survive.”
- Liver: Processes and neutralizes toxins, drugs, and metabolic wastes
- Kidneys: Filter out waste products through urine
- Digestive Tract: Helps eliminate indigestible materials and some metabolic waste
No published medical research shows that juice cleanses enhance or speed up the body’s detoxification systems beyond what they already do on their own. In fact, stripping fruits and vegetables of their fiber—which happens during juicing—removes the component most responsible for supporting digestive health and cholesterol regulation.
What Actually Happens to Your Body During a Juice Cleanse?
Embarking on a juice cleanse launches several changes in your body, many of which may not match the idealized benefits advertised. Below, we break down the physiological responses, short-term effects, and potential risks:
1. Rapid Weight Loss (Mostly Water, Not Fat)
One of the most noticeable changes is temporary weight loss. Most people do drop pounds during a cleanse, but these are largely due to water loss and lower carbohydrate intake, not significant fat loss. Once you resume normal eating, most or all of this weight quickly returns.
What others are reading
- Initial weight loss may be 2–5 pounds after a typical 3-day cleanse
- Most of the weight is water, glycogen, and even muscle mass—not body fat
- Muscle breakdown is common when protein is restricted
Longer-term fat loss is unlikely unless total calories remain significantly reduced and other healthy habits (like exercise) are maintained. Returning to regular eating patterns usually reverses weight loss within days.
2. Blood Sugar Fluctuations
Juices made from fruits and starchy vegetables can deliver a significant dose of naturally occurring sugar. Without the moderating effect of fiber—removed during juicing—blood sugar levels can quickly spike and then drop, causing:
- Light-headedness
- Irritability
- Fatigue
- Headaches
- Heightened risk for those managing diabetes or blood sugar disorders
Without adequate protein or fat, the body lacks long-term energy sources. Constantly drinking juice may produce repeated cycles of sugar highs and subsequent crashes.
3. Loss of Dietary Fiber and Its Consequences
Juice cleanses filter out virtually all of a plant’s fiber, the indigestible portion of fruits and vegetables that feeds healthy gut bacteria, regulates blood sugar, helps manage cholesterol, and supports bowel regularity.
- Lack of fiber may slow digestion, cause irregularity or constipation
- May disrupt healthy composition of gut microbiota over time
- Leads to reduced satiety, potentially increasing post-cleanse hunger and overeating
4. Effects on Energy Levels and Cognitive Clarity
While some report early bursts of energy or mental clarity, many experience a notable lack of energy by day two or three.
- Low-calorie intake can result in fatigue and sluggishness
- Hunger-induced irritability is common
- Those requiring high cognitive or physical performance may be especially affected
5. Digestive and Gastrointestinal Effects
Despite claims of digestive “rest,” evidence supporting the benefit of an all-liquid regimen is lacking. The digestive tract is designed to handle fiber-rich foods, and removing this substrate may actually hinder normal function over time.
6. Effects on Skin and Hydration
Some advocates suggest juice cleanses lead to clearer, glowing skin, though scientific evidence is minimal. If increased water intake occurs during a cleanse, some people may notice temporary improvement in skin hydration, which is unrelated to the juices themselves.
7. Short-Term Changes in Gut Bacteria
Emerging research finds that, over a very short window, juice-only diets can alter the composition of gut microbiota. In a small 2017 study, healthy adults undertaking a 3-day juice cleanse saw changes in their intestinal bacteria, with corresponding short-term weight loss. However, this effect appears temporary and may reflect calorie restriction rather than unique juice properties.
Main Claims vs. Actual Evidence: A Side-by-Side Look
| Claim | Scientific Evidence |
|---|---|
| Detoxifies and removes toxins from the body | No scientific support; liver & kidneys naturally detoxify without external help |
| Leads to long-term weight loss | May cause initial water weight loss; weight typically regains after returning to a regular diet |
| Restores digestive health | Fiber loss may actually impair gut function; not recommended for gut health |
| Boosts energy & mental clarity | Initial feeling of lightness may occur; often followed by fatigue, brain fog |
| Improves skin appearance | Hydration may help temporarily; direct evidence is lacking |
| Nourishes with vitamins and phytonutrients | Juices are rich in certain vitamins, but a well-balanced whole-food diet provides greater overall nutrition and benefits |
Potential Health Risks and Downsides of Juice Cleanses
Despite their popularity, juice cleanses are associated with several downsides—especially when extended over days or weeks:
- Low protein & fat intake: Essential for muscle maintenance, tissue repair, and brain function
- Higher risk of muscle loss due to lack of dietary protein
- Low-calorie diets may slow metabolism, worsening weight gain risk afterwards
- May cause nutrient deficiencies if sustained (B12, iron, calcium, etc.)
- Sugar spikes could be dangerous for individuals with diabetes or metabolic disorders
- Potential kidney stress, especially with high-oxalate vegetables (spinach, beets)
- Irritability, headaches, and fatigue are commonly reported symptoms
- Possible fainting or vision changes in extreme cases
People with certain conditions—such as diabetes, kidney disease, or those who are pregnant or breastfeeding—should avoid juice-only diets.
Any Possible Benefits?
While many claims are exaggerated, there can be a few, mostly short-term benefits to consuming more fruit and vegetable juices as part of a broader, balanced diet:
- Juices deliver concentrated vitamins, minerals, and phytonutrients (such as vitamin C, potassium, various antioxidants)
- May increase awareness of dietary choices and inspire healthier eating habits post-cleanse
- Higher hydration due to higher fluid intake during the cleanse
- Potential exposure to new flavors and plant compounds not regularly consumed
However, these benefits are matched or exceeded by simply incorporating more whole fruits and vegetables—without the downsides and deprivation of a restrictive cleanse.
Who Should Avoid Juice Cleanses?
Juice cleanses are not suitable for everyone, and some people should avoid them altogether:
- People with diabetes or impaired glucose tolerance (risk of blood sugar spikes)
- Those with chronic kidney disease, due to the risk of oxalate accumulation and kidney strain
- Pregnant or breastfeeding women (risk of nutrient deficiencies)
- Children and adolescents, who need balanced nutrients for normal growth
- Anyone with a history of eating disorders (may trigger unhealthy patterns)
Alternatives to Juice Cleansing: How to Support Your Body Sensibly
- Eat a balanced, whole-food diet rich in vegetables, fruits, whole grains, lean proteins, and healthy fats
- Drink plenty of water daily to support natural detoxification
- Minimize ultra-processed foods and added sugars in your diet
- Include a variety of fiber-rich foods to nourish your gut microbiome
- Exercise regularly and get sufficient sleep for metabolic and organ health
Frequently Asked Questions (FAQs)
Q: Can I detox my body with a juice cleanse?
A: No. The liver and kidneys are naturally equipped to remove toxins without help from juice cleanses. There is no scientific evidence that a juice cleanse removes more toxins from your body than your organs already do.
Q: Is the weight loss from a juice cleanse permanent?
A: The weight loss is usually temporary and mostly water, not fat. Once you resume eating regular foods, you will likely regain the lost weight.
Q: Are juice cleanses dangerous?
A: Juice cleanses may be risky for people with diabetes, kidney conditions, or those who are pregnant. Potential side effects include low energy, headaches, dizziness, and blood sugar fluctuations.
Q: Can a juice cleanse improve skin health?
A: Some people notice improved skin hydration due to increased fluid intake, but there is no strong evidence that juice cleanses alone improve skin health long-term.
Q: What’s a healthier alternative to a juice cleanse?
A: Focus on balanced meals with plenty of colorful vegetables, fruits, fiber, whole grains, and lean protein. Drinking enough water and engaging in regular exercise support your body’s natural detoxification processes.
References
- https://www.urmc.rochester.edu/news/publications/health-matters/do-juice-cleanses-detox-the-body
- https://wexnermedical.osu.edu/our-stories/what-you-should-know-about-juice-cleanses
- https://www.healthline.com/nutrition/juice-cleanse
- https://resources.healthgrades.com/right-care/food-nutrition-and-diet/juice-cleanse-what-to-know-about-effectiveness-and-safety
- https://www.medicalnewstoday.com/articles/323136
- https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/juicing/faq-20058020
- https://www.nm.org/healthbeat/healthy-tips/nutrition/is-a-juice-cleanse-good-for-you
- https://www.gundersenhealth.org/health-wellness/eat-move/do-juice-cleanses-really-work
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