New research published in the Open Access journal Nutrients by scientists from Northwestern University, USA, finds that juice cleanses may not be as healthy as we thought. In the study, the researchers found that juice cleanses may induce negative changes to the gut microbiome, as seen through analysis of faecal and oral samples from participants of the study who carried out juice diets.

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

In this article, we will look at how juice cleanses rose to popularity and explore the latest study on its effect on the microbiome.

A brief history on juice cleanses

Juice cleanses became popular in the late 1990s and early 2000s and became prominent in mainstream media, with celebrities like Beyonce endorsing the diet in 2006. The diet was based on the misconstrued perception that people’s bodies required ‘detoxification’. It also stemmed from recommended diet regimes branching from popular Western beauty trends, where weight loss was glorified and the prominent goal for many, particularly women.

The supposed health benefits of juice cleanses were also praised by entrepreneur Peter Glickman, author of ‘The Master Cleanse Coach’, who sold the idea that the regime could remove toxins from the body, enable weight loss and boost energy levels.

Juice cleanses induce weight loss due to the insufficient number of calories consumed. However, there is also an immense lack of essential nutrients consumed if juices are the only component present in one’s diet. This includes nutrients like proteins and fibre which are required by the body to function optimally. Thus, the health benefits of juice cleanses are put into question.

The novel study shows empirical evidence that the cleanse intrinsically changes the composition of our microbiomes, suggesting that weight loss regimes like juice cleanses may not always serve our overall health.

The importance of the gut microbiome

The gut microbiome is the diverse range of microbes, like bacteria and yeast, that are present in our gut. The composition of the microbiome is subject to change and is impacted by the foods we eat. There has been a recent surge in research on the gut microbiome overall and how it links to different aspects of our health and disease.

The gut–brain axis plays an important role in regulating key processes in our body. For example, recent research suggests there is a bidirectional relationship between our gut health and our mental health, highlighting the importance of our gut microbiome and how its composition may be integral to how we feel. Thus, it is essential to understand how different diets, particularly strict ones, may affect the microbiome, which in turn may affect our health.

Juice cleanses affect the composition of the gut microbiome

In the study, scientists rounded up fourteen participants to take part in three different diets—one consisting solely of juice, one with juice and food and one with only plant-based whole food. The study aimed to see how these diets affected the gut, specifically the gut microbiome.

To see how the juice cleanses affected the composition of the microbiome, researchers took microbiome samples from all participants; this included their stool (gut microbiome), saliva and swabs of their inner cheeks (oral microbiome). The samples were taken before the diet commenced, immediately after it started and fourteen days after it started. The RNA from the samples were analysed to provide information on the composition of the microbiome and results at each stage were compared.

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 – Dr. Melinda Ring.

The results showed that a diet based exclusively on juice induced changes in the compositions of both the oral and gut microbiota. The changes displayed a surge in bacteria which were pro-inflammatory and linked to gut permeability and cognitive decline. Therefore, the results suggested that juice cleanses induced changes in the oral and gut microbiomes which were associated with negative health impacts.

The value of a diverse diet

Fibre is an essential component of our diet that is crucial to our health. Reduced fibre intake has been associated with many inflammatory conditions, and an increased intake of fibre is linked to a reduced risk of bowel cancer.

Juices are void of the fibre that is usually consumed with the fruit when whole; therefore, doctors would not recommend the diet as a replacement for meals. The lack of fibre in juices means that the sugar present in the fruit is more readily absorbed into the bloodstream, causing a sugar spike. Furthermore, the beneficial gut bacteria are unable to thrive without fibre, and the consistently high sugar content fuels the growth of harmful bacteria.

In the same study, researchers found that an elimination diet carried out by the same participants before the juice cleanse induced positive changes to the oral and gut microbiome. The diet consisted of organic whole foods high in fibre such as fresh fruit and vegetables, eggs and 8 glasses of water. They were also asked to cut out caffeine, alcohol, processed sugar, red meat, gluten and dairy.

The results showed an increase in ‘good’ bacteria, such as Faecalibacterium prausnitzii, which produces Byruvate. This compound is a key component that promotes gut health and protects against disease like colorectal cancer.

Research on the effects of popular diets on our health is important for people to make informed decisions about their food choices and keep healthy. Juices are devoid of key nutrients like proteins, fats and minerals required by the body for essential processes including movement, digestion and cognitive function. Maintaining a diet consisting of diverse foods with a range of nutrients is key to staying healthy.

Research is now showing how diet plays a crucial role in our cognitive function, and how this is linked to the gut microbiome. Read more research like this published in Nutrients, or access the full journal list.