Study links juice-only diets to increased harmful gut bacteria and potential cognitive decline

"Detox regimes" featuring pressed juices have become incredibly popular in recent years. Promises of improving digestion, achieving a flat stomach, losing weight, and boosting overall health sound enticing to consumers and promise good profits to companies. Unfortunately, many people are unaware that living on juices, even for a short period, is a controversial practice that nutrition and medical experts do not recommend at all.

Recently, study results were published indicating that consuming only juices, even for a short period, can cause significant damage to the gut microflora and exacerbate chronic inflammatory conditions in the body.

Researchers who conducted this study, published in the scientific journal Nutrients, state that a juice "detox" can wreak havoc on the microbiome even in the short term. Knowing that the beneficial impact of a healthy microflora extends far beyond just the digestive organs, it is not surprising that these scientists warn that the potentially adverse effects of detox regimes can even negatively affect mental health.

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What the Juice Detox Study Revealed

The study in question recruited a group of 14 people and had them follow one of three dietary regimes for three days:

• Only juices
• Juices + food
• Plant-based diet without juices

Participants had stool and saliva samples taken before starting to record the baseline state of the microbiome in the colon and oral cavity, then again immediately after the diet, and once more 14 days later. Researchers found that people on a juice-only diet developed an abundance of harmful, "pro-inflammatory" bacteria. They believe this is directly linked to the high sugar content and the complete lack of fiber in a juice-based diet.

Participants on the juice-only diet also exhibited bacteria associated with "leaky gut" (a condition where the small intestine's ability to control what passes into the bloodstream is compromised), inflammatory processes, and cognitive decline. Crucially, these negative changes in the microbiome were found only in the study participants who consumed exclusively juices.

Based on these findings, the authors concluded that even a short, 3-day juice-only diet can negatively impact the microflora. This adds to a growing body of evidence showing that daily dietary choices quickly affect the state of the microbiome and, consequently, overall health.

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The Problem with Missing Fiber

Gastroenterologists commenting on the study's findings note that although the sample size was small, the results are certainly alarming. It makes it clear that the nutritional content of any diet must be considered carefully. Since juices are mostly devoid of fiber, what remains is essentially water and concentrated sugar. It is a well-established medical fact that a low-fiber, high-sugar diet is detrimental to both general health and the microflora.

The juicing process removes insoluble fibers, which are vital for regular bowel movements and are strictly necessary for feeding the good bacteria that maintain the integrity of the colon wall. The absence of this fiber can lead to the rapid overgrowth of "bad" bacterial strains that thrive on sugar, such as Proteobacteria, which are strongly associated with inflammatory processes. In other words, the microflora is literally a reflection of the daily diet.

Is Cleansing or Detoxing with Juices Actually Healthy?

No, this practice is definitely not considered healthy by the vast majority of nutrition experts. All those promises of rapid weight loss and body detoxification may sound appealing, but even some seemingly positive results of these "treatments" are highly misleading. When people lose a few pounds by drinking only juices, it happens simply because they consume a calorie deficit and expel more fluid. Thus, most of the weight lost this way is actually just excess water weight.

Not only does "body cleansing" with juices disrupt the balance and vitality of the microbiome - which is essential for good digestion and a strong immune system - but it is also very bad for blood sugar control. An all-juice diet can cause severe, sudden spikes followed by rapid, exhausting drops in blood sugar levels.

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What Experts Recommend Instead

Experts are strictly against consuming only juices, even in the short term. For those who love freshly pressed juices, the recommendation is to consume them moderately and always in combination with fiber-rich foods, such as nuts, seeds, and whole grains.

Ultimately, it is highly advisable to eat whole fruits and vegetables, along with quality proteins (preferably plant-based), healthy fats, and plenty of water. This is the absolute best way to help the body detoxify itself using its own natural mechanisms and its two powerful, built-in detox organs: the liver and the kidneys.

Of course, consuming freshly pressed juices occasionally can be part of a healthy diet, as it provides a quick boost of micronutrients and antioxidants. It is important to understand that expert warnings against pressed juices refer exclusively to using them as meal replacements or as the sole source of nutrients for any period of time.