Gut cleanses and gut restoration: What they can and cannot do

The essentials at a glance

• There is no evidence that probiotic supplements provide any benefit for healthy individuals; the EFSA has not approved a single health claim for them.
• Colonic irrigation is barely studied and carries risks such as electrolyte imbalances, infections, and intestinal wall injuries.
• The German Nutrition Society (DGE) recommends at least 30 g of fiber per day, yet the average intake is only 18 to 19 g.
• A ten-day Buchinger fast caused a measurable shift in the gut flora of fifteen healthy men, but it returned to its previous state after three months.
• At the Tannerhof, the refeeding phase after fasting lasts about one-third of the fasting period and leads back to a fiber-rich diet.

What do gut cleanses, gut restoration, and gut detox programs promise?

The gut is a major concern for many people looking to take a break for their health, so it is good to know that medically supervised Buchinger therapeutic fasting supports the gut differently than the grand promises of advertising suggest: If you are considering a gut cleanse, you can instead book a fasting week with a refeeding phase at the Tannerhof nature hotel and have your gut supported as part of a medically supervised program. From a medical perspective, the terms gut cleanse, gut restoration, and gut detox do not actually mean anything. None of them are defined, and none describe a recognized procedure. They are marketing terms used to sell a wide variety of offerings: capsules containing bacterial cultures, colonics offered under the name colon hydrotherapy, or powders and cleanses intended to "cleanse" the gut from within. Their actual effectiveness can only be determined by the available evidence.

Bacterial supplements: few facts, many promises

Probiotic supplements promise a lot, from a stronger immune system to better digestion. However, there is no evidence that taking these microorganisms provides any benefit for healthy people. To this day, the European Food Safety Authority (EFSA) has not approved any health-related advertising claims for dietary supplements containing specific bacterial cultures, and the term "probiotic" is considered an unauthorized claim. A study by the CVUA Karlsruhe shows that the quality of these supplements varies: 27 percent of the products tested did not contain the amount of bacteria claimed on the label. After antibiotic treatment, bacterial supplements can even delay the recovery of the natural gut flora.

Colonics: barely researched, not risk-free

Colonic irrigation is offered for various ailments, even though it has hardly been scientifically studied. Whether it has any benefit is unclear, while its risks are well-documented: electrolyte imbalances, infections, and injuries to the intestinal wall.

And what about the gut itself? It is not a vessel that fills up and gets clogged; it is an organ with a lining that renews itself at short intervals and a gut flora that changes daily and is as unique as a fingerprint. Therefore, there is no such thing as a cleanse that "restores" it. What does exist is a diet that nourishes its bacteria.

How can you actually build up your microbiome?

The microbiome is not built up, but nourished. Fiber from vegetables, legumes, whole grains, nuts, and berries reaches the large intestine undigested, where gut bacteria ferment it. This process produces short-chain fatty acids, which the body uses as an energy source and which are linked to the health of the intestinal lining. This effect happens on your plate, not in a capsule.

The guideline from the German Nutrition Society is at least 30 g of fiber per day. In reality, women in Germany eat an average of 18 g and men 19 g. This gap between the guideline and daily life is the real starting point, and it can be narrowed with simple measures:

• At least three servings of vegetables daily, ideally including one serving of legumes such as lentils, chickpeas, or fava beans.
• Whole grains instead of white flour: whole-grain pasta provides about twice as much fiber as peeled durum wheat pasta.
• Nuts, seeds, and berries as natural sources of fiber, for example, ground flaxseeds sprinkled over breakfast.
• Fermented foods like yogurt with live cultures as an everyday source; the only health claim approved by the EFSA relates specifically to these yogurt cultures.
• Combine fiber from various sources, increase the amount slowly, and drink plenty of fluids, as whole grains absorb water.

None of these tips cost more than a little attention while shopping. They work because they are repeated daily, and that is exactly what distinguishes them from any fad diet that promises results lasting only a few weeks.

How does fasting change the gut?

Fasting changes the microbiome in a measurable but reversible way; it does not "cleanse" it. The best-studied example to date is a small study in which fifteen healthy men fasted for ten days according to Buchinger guidelines. The composition of their microbiome shifted: bacteria that break down dietary components, such as those from the Lachnospiraceae and Ruminococcaceae families, decreased, while bacteria that utilize the body's own substrates increased. After three months, the shift had reversed. The authors interpret this change as part of the physiological adaptation to fasting, not as a cleansing process. Due to the small number of participants, no general conclusions about the effects of fasting can be drawn from this.

The bowel cleansing at the start of a fast can also be viewed realistically. According to the Ärztegesellschaft Heilfasten und Ernährung (ÄGHE), the one-time administration of Glauber's salt and repeated water enemas as part of a fasting therapy are not considered harmful. Flushing out the gut flora lining the intestinal wall is unlikely because it adheres firmly to the intestinal mucosa; however, research on the effects on the microbiome is still limited.

What happens during fasting is a transition: the body switches from external to internal nutrition, the metabolism shifts to fatty acids and ketone bodies, and the microbiome follows this movement as long as it lasts. The body is guided back through the reintroduction of food, which is firmly anchored in the fasting process. Fasting is therefore a physiological break with a consciously designed conclusion, not a gut cleanse, and those who understand it as such gain more from it.

How does Tannerhof support the gut during fasting?

At our facility, Buchinger therapeutic fasting follows a clear arc that begins and ends with the gut. We start on the first day of fasting with a medical consultation, followed by Glauber's salt, a saline laxative, to initiate bowel cleansing and open the fasting period. Enemas or additional salt doses are possible but not mandatory. They do not enhance the quality of autophagy processes but rather contribute to well-being during the fast. Throughout the fasting days, we support the metabolism with herbal tea, mild vegetable broth, and freshly pressed juices, supplemented by Kneipp contrast showers, hay flower wraps, and massages that keep the circulation in check.

• Medical consultation on the first day of fasting, including medical history, examination, and bioimpedance analysis.
• Bowel cleansing at the start of the fast (can be adapted individually), enemas possible three times a week.
• Fasting period with liquid nutrition according to Buchinger and accompanying treatments.
• Reintroduction of food over about one-third of the fasting duration, starting with the breaking of the fast.
• Final medical consultation with recommendations for daily life.

For us, the reintroduction of food is the real bridge. Every bite is chewed consciously, and the diet returns to vegetables, whole grains, and fresh produce—exactly the foods that sustainably nourish the gut flora. In the final consultation, every guest receives a recommendation for their daily life, as we see the fasting week as the starting point of a dietary change, not its result. Those who want to strengthen their gut begin during the fast and continue afterward with fiber, day by day.

Understood this way, a fasting period is not a cure that "sanitizes" something, but a break from which a different diet can emerge. For guests with health concerns, a fasting period of at least ten pure fasting days under medical supervision is recommended, as only this duration allows the transition and the reintroduction of food to settle. Medically supervised therapeutic fasting according to the Buchinger method combines fasting days with medical diagnostics and a reintroduction phase that starts exactly at this point. If you would like to take your gut health seriously, you can request your fasting week with food reintroduction directly via Body Detox Therapeutic Fasting.