How a juice cleanse can mess with your gut, metabolism, immunity

When life gives you lemons — don’t juice them!

Juice cleanses are a short-term diet of only vegetable or fruit juices to detoxify the body, improve digestion and lose weight.

Though they have become immensely popular, a new study finds that even a three-day cleanse can negatively affect gut and oral bacteria, potentially leading to long-term health consequences.

A new study finds that even a three-day juice cleanse can harm the gut. Pixel-Shot – stock.adobe.com

“Most people think of juicing as a healthy cleanse, but this study offers a reality check,” said senior study author Dr. Melinda Ring, director of the Osher Center for Integrative Health at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician.

For the study, a group of healthy adults only drank juice, another consumed juice with whole foods and a third group ate only whole plant-based foods.

The researchers analyzed bacterial changes via saliva, cheek swabs and stool samples before, during and after the experimentation.

The juice-only group had the most significant increase in bacteria linked to inflammation and gut permeability, while the juice-plus-food group had less severe bacterial changes.

The whole-food group saw more beneficial microbial shifts, leading the researchers to suggest that juicing without fiber may disrupt the gut microbiome — the collection of bacteria, viruses and fungi in the digestive system.

“Consuming large amounts of juice with little fiber may lead to microbiome imbalances that could have negative consequences, such as inflammation and reduced gut health,” Ring explained.

Juicing a fruit or vegetable can reduce its fiber content, and fiber is important to the body. franz12 – stock.adobe.com

Ring reports that juicing strips away much of the fiber in whole fruits and vegetables. Fiber is said to feed healthy gut bacteria, as well as facilitate smooth and regular bowel movements, help control blood sugar, lower cholesterol and lessen the risk of heart disease and stroke.

Reduced fiber intake may affect metabolism, immunity and even mental health, Ring said.

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Fiber keeps sugar-loving bacteria at bay, while the excessive sugar in juice fuels the harmful bacteria.

In the mouths of the juice dieters, Ring’s team noted a reduction in beneficial Firmicutes bacteria and an increase in inflammation-linked Proteobacteria.

“This highlights how quickly dietary choices can influence health-related bacterial populations,” Ring said of the study. “The oral microbiome appears to be a rapid barometer of dietary impact.”

The findings were published recently in the journal Nutrients, confirming other research suggesting that juice fasts disrupt the gut microbiome.

If you can’t give up juice, trying pairing it with whole foods and vegetables so you can get that all-important fiber. lindahughes – stock.adobe.com

The Northwestern study authors are calling for additional research on juice’s health effects, especially in children, who often drink it as a substitute for fruit. In the meantime, the researchers hope your fiber intake is up to snuff.

The American Heart Association recommends getting at least 25 to 30 grams of fiber a day from food — most Americans only consume around 15 grams a day.

“If you love juicing, consider blending instead to keep the fiber intact, or pair juices with whole foods to balance the impact on your microbiome,” Ring advised.