A recent study has uncovered unexpected consequences of juice fasts, even those as brief as three days, on the oral microbiome. Juice cleanses, touted for their supposed detoxifying and weight loss benefits, involve the consumption of only fruit and vegetable juices for a short period. Despite claims of health advantages, there is scant scientific evidence to support these assertions, and the new study suggests that these cleanses may, in fact, be detrimental to one’s health.
The study, which involved a small sample size, revealed that a three-day juice cleanse can disrupt a person’s microbiome, promoting the growth of inflammatory bacteria while depleting beneficial strains. Advocates market juice cleanses as a means to eliminate toxins, shed pounds, and modulate gut bacteria linked to weight loss. However, the actual benefits remain largely anecdotal, and there are potential risks associated with adopting a juice-only diet.
The Food and Drug Administration (FDA) has cautioned against the use of detox/cleansing products due to potential inclusion of harmful substances and misleading health claims, which may pose risks to individuals with certain medical conditions such as diabetes. Furthermore, a juice-only regimen may not supply adequate nutrients or energy, and is unlikely to result in sustainable weight loss.
Registered Dietician Megan Mehnert from Bristol, UK, emphasized the need for caution in interpreting the study’s findings, citing limitations such as the small sample size and short intervention duration. The study, published in MDPI Nutrients, reported changes in oral microbiome composition following a 3-day juice cleanse, with an increase in inflammatory bacteria and a decrease in beneficial types.
During the study, participants – all healthy and medication-free – underwent a 3-day elimination diet before being assigned to one of three groups for a subsequent 3-day intervention diet period. These groups included a ‘juice fast’ consuming cold-pressed fruit and vegetable juice, individuals on a regular diet supplemented with juices, and those adhering to a plant-based whole food diet. The study highlights the potential risks associated with short-term juice cleanses and the importance of considering individual health requirements before embarking on such trends.
Following a brief reintroduction diet, participants in the study resumed their normal eating habits. The research team gathered samples of saliva, cheek cells, and feces at various points throughout the study – at the beginning, after the elimination diet, following the intervention diets, and finally, 14 days post-study completion. DNA analysis was performed to identify the types of bacteria present in the samples.
During the elimination diet phase, minimal changes were observed in the microbiomes of the cheek, gut, and saliva. However, after the 3-day intervention diet, individuals who underwent a juice fast experienced significant alterations in the composition of their cheek and saliva microbiota. Notably, the presence of Proteobacteria, which are known to be linked with various inflammatory conditions, increased while the levels of Firmicutes, essential for fermenting dietary fiber, decreased. Similar albeit less pronounced modifications were detected in individuals on the other two diets.
Interestingly, no substantial shifts were found in the gut microbiota of any group following the different dietary interventions. Nevertheless, participants on the juice fast exhibited an elevated abundance of microorganisms associated with proinflammatory processes. Upon reevaluation after the 14-day post-intervention period, most individuals’ microbiomes seemed to be returning to their baseline states.
The researchers highlighted potential negative health implications of these bacterial changes, noting that the increased abundance of certain taxa in response to the juice-based diets could contribute to elevated inflammatory markers, as well as the development of conditions like colorectal cancer, cardiovascular diseases, gingivitis, and periodontal diseases. Megan Mehnert emphasized that juice fasting should not be viewed as a quick fix for health issues. She also cautioned against the potential harm, particularly for individuals with eating disorders, highlighting that such restrictive diets lacking essential nutrients may further compromise health and instill fear of food.
Mehnert stressed the importance of balanced nutrition over quick fixes, emphasizing the liver and kidneys’ natural detoxification processes. While fruit and vegetable juices can be part of a healthy diet, excessive reliance on them may introduce high levels of free sugars. Mehnert recommended a diet comprising balanced meals and snacks throughout the day, incorporating a diversity of foods from all food groups to ensure adequate nutrition for optimal health.
The study contributes additional evidence, albeit limited, suggesting the questionable benefits and potential risks associated with juice cleanses. Mehnert’s advice underscores the importance of maintaining a well-rounded diet to support overall health, cautioning against restrictive eating patterns that may lead to nutritional imbalances.
