Juice fasts, short-term dietary regimens involving the consumption of only fruit and vegetable juices, have gained considerable popularity. Marketed as a way to remove toxins, aid digestion, and promote weight loss, these cleanses typically last from three to seven days. However, the scientific community remains skeptical about the purported health benefits, and emerging research suggests that juice fasts may even pose potential health risks. This article delves into the benefits and risks of a 3-day juice fast, providing a comprehensive overview of the current scientific understanding.
What is a Juice Cleanse?
A juice cleanse involves consuming only fruit and vegetable juices for a short period, usually between 3 and 7 days. People can make their own juices from fresh or frozen fruits and vegetables or buy commercially available varieties.
Purported Benefits of Juice Cleanses
Advocates of juice cleanses claim several health benefits, including:
- Removing toxins from the body
- Promoting weight loss
- Altering gut bacteria to encourage those associated with weight loss
- Improving skin condition
However, it's important to note that most evidence supporting these claims is anecdotal.
Juicing for Health
Fruits and vegetables are rich in active compounds that can benefit overall health and help prevent chronic conditions. They are a good source of phenolic compounds, which have antioxidant, immune-supporting, and antibacterial properties. Fruit juices may also help lower blood pressure and cholesterol levels.
Read also: Benefits of Juice Fasting
Juicing for Weight Loss
Juice cleanses may 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. They experienced substantial weight losses that lasted after the study ended. The researchers concluded this may be due to changes in the participants’ gut bacteria.
However, it’s important to note that the participants only consumed 1,310 calories per day. This is below the number of daily calories recommended by the “Dietary Guidelines for Americans 2020-2025” for weight maintenance, which is at least 1,600 calories for adult females and 2,000 for adult males. As such, being in a calorie deficit could lead to rapid weight loss.
Juicing to 'Detox'
Some detox treatments have been shown to improve liver detoxification and remove environmental pollutants from the body. However, the authors of a 2015 review suggest that these clinical studies have significant flaws in methodology and low participant numbers. Much of the promoted evidence also comes from animal research, which can’t necessarily be applied to humans.
Juicing for Skin Health
However, these are both animal studies. More studies with humans are needed before any conclusions can be drawn.
Potential Risks and Downsides of Juice Cleanses
Despite the claims of health benefits, juice-only diets pose several potential risks:
Read also: Healthier alternatives to juice cleanses
- Inadequate energy and nutrients: A juice-only diet is unlikely to provide enough energy or nutrients.
- Harmful ingredients: Some detox/cleansing products may contain illegal or potentially harmful ingredients and be marketed using false health claims. The Food and Drug Administration (FDA) warns that this could be harmful for people with some health conditions, such as diabetes.
- Increased inflammatory bacteria: A recent study found that even three days of a juice cleanse appears to alter a person’s microbiome, increasing inflammatory bacteria and decreasing those that are beneficial to health.
- Potential harm to the oral microbiome: A new Northwestern University study suggests that juice cleansing might actually be harmful for your health, triggering shifts in gut and oral bacteria linked to inflammation and cognitive decline after just three days.
- Unlikely to lead to lasting weight loss: Juice-only diets rarely lead to lasting weight loss. The weight ‘lost’ is simply water weight that can easily be gained back.
A Closer Look at a Recent Study
A study published in MDPI Nutrients investigated the impact of a 3-day juice cleanse on the oral microbiome. The study involved 14 participants with a mean age of 22.7 years. At the start of the 21-day study, the participants underwent a 3-day elimination diet, during which time they ate organic fresh fruits, vegetables, gluten-free whole grains, and eggs, as well as drinking 8 glasses of water a day. Researchers told them to avoid caffeine, alcohol, sugar, processed foods, dairy, red meat and gluten. Researchers collected saliva, cheek swabs, and stool samples before, during, and two weeks after the three-day diet intervention to analyze bacterial changes using gene-sequencing techniques. They extracted DNA to identify the bacteria in the samples.
On the elimination diet, the researchers detected few changes in the cheek, gut or saliva microbiome. However, after the 3-day intervention diet, people on the juice fast had significant changes in the relative abundance of their cheek and saliva microbiota. The tests revealed an increase in Proteobacteria, which are associated with many inflammatory diseases, including those of the gut, and a decrease in Firmicutes, which are important for fermenting dietary fiber. Similar but much smaller changes were seen in people on the two other diets.
The researchers did not detect any significant changes in the gut microbiota in any of the groups following the different diets, but they did see an increase in the relative abundance of microorganisms linked to proinflammatory activity in those on the juice fast. When they tested at the end of the 14 days post-intervention, the researchers found that most people’s microbiomes were returning to normal.
The authors suggest that the changes could have negative impacts on health, stating: “many of the taxa that increased in relative abundance in response to the juice and juice plus food diets have been identified as potential critical risk factors for their involvement in increasing inflammatory markers, colorectal cancer, cardiovascular disease, gingivitis, and periodontal disease.”
The Role of Fiber
The lack of fiber in the juicing diet may be driving the disruption, the authors wrote. 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 may fuel harmful bacteria, according to the authors. Fiber also helps slow digestion and the absorption of sugar.
Read also: 7-Day Juice Cleanse
Expert Opinions
Megan Mehnert, a UK Registered Dietician, urged caution when interpreting the findings, noting the small sample size, short intervention period, and the population group not being representative of the wider population. She also cautioned that juice fasts should not be regarded as a quick health fix and could be particularly damaging for people with eating disorders.
“Generally there is no quick fix to improve health and for most of us, our liver and kidneys do a good job at detoxing the body. Fruit and vegetable juices can be part of a healthy balanced diet - UK Public Health England recommends that a small glass of fruit juice of 150ml a day counts toward your ‘5 a day’, but no more as juices are high in free sugar,” she said.
Melinda Ring, MD, a physician at Northwestern Medicine, stated that “Most people think of juicing as a healthy cleanse, but this study offers a reality check."
Potential for Disordered Eating
Most people who do juice cleanses don’t eat enough solid food to meet their energy needs. This may lead to increased hunger and energy restrictions that could cause symptoms like: tiredness, headaches, irritability. 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.
Weight Loss and Juice Cleanses
It’s possible to lose weight on a juice cleanse, but this is likely to be water weight, rather than fat. It’s important to note that after a few days of juice cleansing, you may also start to lose muscle mass. Maintaining muscle mass during weight loss is very important for your general health. The authors of a 2017 study found that participants lost up to 1.2kg after a 3-day juice cleanse.
Alternatives to Juice Cleanses
If you're looking to improve your health, there are more sustainable and evidence-based approaches than juice cleanses:
- Focus on a balanced diet: Aim to have balanced meals and snacks regularly throughout the day, with a focus on including a variety of different foods from all food groups.
- Incorporate whole foods: A nutritious diet filled with whole foods is key for optimal health and disease prevention.
- Stay hydrated: Drink plenty of water throughout the day.
- Minimize added sugars: Reduce your intake of processed foods and sugary drinks.
- Consider blending instead of juicing: If you enjoy juicing, consider blending rather than juicing to retain fiber. Or pair juices with whole foods to balance the impact on your microbiome.
Juices as part of a balanced diet
For those who have trouble getting a variety of vitamins, minerals, and phytonutrients into their diets on a regular basis, juices can be incorporated. “Because the juices are raw, the vitamins are retained,” she says. Nutrients in juice include antioxidants, which are crucial for supporting our immune systems and protecting against chronic conditions like cancer and heart disease. Additionally, juices can increase hydration, which improves digestion.
The Importance of Consulting a Professional
Speak with a healthcare professional or registered dietitian if you’re concerned about your diet. Consider connecting with a registered dietitian or healthcare professional to help achieve your health and weight-loss goals.