Juice cleanses promise glowing skin, effortless weight loss, and a healthy dose of vitamins, but you may want to think twice before swapping solid food for bottles of liquified vegetables because they could actually be doing you more harm than good.
A new study has shown that going on a vegetable and fruit juice diet for just three days can lead to changes in gut and oral bacteria associated with inflammation and cognitive decline. To come to this conclusion, scientists from Northwestern University examined three groups of healthy adults.
One group consumed nothing but juice, another group had juice with whole foods, and a third ate only whole plant-based foods.
The researchers collected saliva, cheek swabs, and stool samples before and after the diets to examine bacterial changes.
The juice-only group exhibited the most significant increase in bacteria linked to inflammation and gut permeability. Meanwhile, more favorable microbial changes were observed among the plant-based whole foods group.
The group that consumed both juice and food showed bacterial changes as well, but they were less severe than the juice-only group.
The findings suggest that juicing without fiber intake may disrupt the microbiome and possibly result in long-term health consequences.
"Most people think of juicing as a healthy cleanse, but this study offers a reality check," said Dr. Melinda Ring, the senior author of the study and a physician at Northwestern Medicine.
"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."
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Juicing strips away essential fiber in whole fruits and vegetables. This fiber feeds beneficial bacteria that produce anti-inflammatory compounds like butyrate.
Furthermore, sugar-loving bacteria thrive in the absence of fiber. Juice has a high sugar content, which fuels these harmful bacteria and disrupts the gut and oral microbiome.
The oral microbiome showed pronounced changes during the juice-only diet. There was a decrease in the beneficial Firmicutes bacteria and an increase in Proteobacteria, which is associated with inflammation.
Overall, the study highlights how quickly dietary choices can influence bacteria in the body. More research is needed to determine how juicing and other diets impact the microbiome, particularly in children, who often drink juice as a substitute for fruit.
"The nutritional composition of juice diets -- specifically their sugar and carbohydrate levels -- plays a key role in shaping microbial dynamics in both the gut and oral cavity and should be carefully considered," said Maria Luisa Savo Sardaro, the first study author and a research associate at Northwestern University.
It is important that fiber is prioritized in diets and food production. If you're a fan of juicing, consider blending your fruits and veggies instead to keep the fiber intact. Or, you can pair juices with whole foods to maintain a balanced diet and microbiome.