By JERUSALEM POST STAFF

A study found that a three-day juice-only diet can harm health, disrupting gut and oral microbiota, leading to inflammation and cognitive decline.

A recent study conducted by researchers from Northwestern University's Feinberg School of Medicine revealed that following a diet based solely on vegetable and fruit juices—even for just three days—can be harmful to health, leading to disruptions in gut and oral microbiota associated with inflammation and cognitive decline.

The study involved 14 healthy adults aged 18 to 35, who were randomly assigned to follow one of three dietary patterns for three days: an exclusive juice fast, a diet combining juice with regular food, or a plant-based whole food diet. According to Femme Actuelle, researchers collected saliva, cheek swabs, and stool samples from participants before, during, and after the juice diet to analyze bacterial changes using gene-sequencing techniques.

The results showed that the group that limited themselves to cold juices experienced the largest increase in the amount of bacteria that cause inflammation and digestive disorders. Studyfinds.org reported that juice-only diets led to decreases in beneficial oral bacteria that help maintain oral health. Participants following juice-based diets showed rapid changes in their oral bacteria, including a reduction in beneficial Firmicutes and an increase in pro-inflammatory Proteobacteria, which are linked to inflammation and cognitive decline.

“Consuming large amounts of juice with little fiber can lead to imbalances in the microbiome that could have negative consequences, such as inflammation and reduced gut health,” said Dr. Melinda Ring, the researcher behind the study. Juicing whole fruits and vegetables leads to the loss of most of the fiber they contain, which is essential for regulating digestion and supporting beneficial gut bacteria.

Without fiber, sugar-loving bacteria can multiply, leading to microbiome imbalances and potential health issues. The high sugar content in juices feeds harmful bacteria, disrupting the microbiome of the gut and mouth. Consuming juice without fiber can alter the microbiome, promoting the growth of harmful bacteria and causing inflammation, which may negatively affect immunity and general health.

The plant-based whole food group experienced more favorable microbial changes, with an increase in beneficial bacteria that support body health, while volunteers who consumed plant-based foods achieved the best balance at the bacterial and microbial level. The juice plus whole foods group had some bacterial shifts, but they were less severe than in the juice-only group, which exhibited the most dramatic shifts in bacterial communities.

“These rapid changes demonstrate that even a short period without fiber can alter our bacterial balance,” said Dr. Ring, as reported by Femme Actuelle. “If you enjoy juices, try making smoothies instead to retain the dietary fiber, or combine your juices with whole foods to balance the impact on the microbiome,” suggested Dr. Ring.

“The nutritional composition of juices, particularly sugar and carbohydrate levels, plays a crucial role in shaping the microbial balance in both the gut and the oral cavity and should be taken into account,” stated Maria Luisa Savo Sardaro, the first author and researcher at the Amato Lab of the Department of Anthropology at Northwestern University.

According to Femme Actuelle, juice cleanses and juice-based detox systems have gained immense popularity, with 26% of consumers trying these programs for perceived benefits like detoxification and improved digestion, despite potential risks.

While gut bacteria proved more resilient to short-term dietary changes, the researchers observed subtle shifts that raised potential concerns. “Participants who consumed plant-based foods achieved the best balance at the bacterial and microbial level,” the researchers noted.