A juice cleanse involves consuming only juiced fruits and vegetables for a prescribed period of time. Advocates of this type of detox claim it removes toxins from the body and aids weight loss.

You might assume it is a healthy choice. What could go wrong ? Plenty, researchers at Northwestern University found. Their research shows that even if you're on a vegetable and fruit juice diet for just a few days, you'll be putting your health at risk. The dramatic changes in our body's balance of gut and oral bacteria brought on by this type of juice cleanse triggers inflammation and cognitive decline.

The juice-only group suffered the most damaging consequences, showing significant increases in bacteria-associated gut permeability and inflammation.

Researchers came to this determination after studying three groups of healthy adults. One group consumed only juice. A second group had juice along with whole foods. The third ate a diet of only plant-based foods. The team collected the participants' saliva, cheek swabs and stool samples during and after their diets.

Next, using gene-sequencing techniques, the scientists looked for any bacterial changes and found the juice-only group suffered the most damaging consequences. Specifically, this group showed significant increases in the kinds of bacteria associated with gut permeability and inflammation.

The juice plus food group had some bacterial shifts, but they were less severe than the juice-only diet. In contrast, the plant-based whole food group showed favorable microbial changes.

These results suggest that juicing without including fiber has the potential to disrupt our body's microbiome. This can lead to long-term negative consequences on our health.

“Most people think of juicing as a healthy cleanse, but this study offers a reality check,” the study's senior author, Dr. Melinda Ring, said in a press release. Ring is the director of the Osher Center for Integrative Health at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician. She agrees that cleanses involving only fruit and vegetable juices are a risky choice.

Fiber is an important nutritional element in our diets because it feeds beneficial bacteria that produce anti-inflammatory compounds. Without fiber, sugar-loving bacteria multiplies and disrupts the gut and oral microbiome. The process of juicing strips away much of the valuable fiber in whole fruits and vegetables.

The study also pointed to the way reduced fiber intake from the juice-only diet may impact metabolism, immunity and even mental health as a result of the changes in the oral microbiome. In particular, the scientists reported a reduction in beneficial Firmicutes bacteria and an increase in Proteobacteria, a bacterial group associated with inflammation.

Use a blender to keep the fiber intact, or pair juices with whole foods to balance the impact on your microbiome.

“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 recommends.

The findings point to a need for additional research on how juice and other restrictive diets impact the microbiome, the authors stress. This is especially important for children since they often consume juice instead of eating whole fiber-rich fruits.

Ultimately, the best choice of all is a diet rich in whole foods, lean protein and fiber.

The study is published in the journal Nutrients.