Intestinal cleansing: what’s behind it and what the evidence shows

9. September 2026 ca. 16 Minuten

What to expect in this article

1. What the intestine already does every day
2. What is supported by evidence about “cleansing” and “detoxing”
3. What experts mean when they say intestinal cleansing
4. What purging costs the body
5. Four things that may be called intestinal cleansing
6. Why a cleanse still feels good
7. Common claims backed by evidence: a fact check of three statements
8. When gut restoration has a tangible rationale
9. What a gut flora test shows before and after a cleanse
10. What you can do now
Frequently asked questions
Sources

What the intestine already does every day

Before considering cleansing the intestines, it is worth looking at what happens there without any intervention. According to the Institute for Quality and Efficiency in Health Care (IQWiG, 2026), the large intestine is about 1 to 1.5 meters long. Its main task is unremarkable: “In the large intestine, even more water, along with salts, is removed from the liquid food pulp.”

This is no minor matter. In the workplace analogy, the intestine is less a waste bin than a recovery plant: it reclaims what the body can still use from what passes through.

The figures already capture the whole conflict. On one side, an organ that reclaims water and salts. On the other, a promise of weight loss that aims to interrupt this very process.

What is supported by evidence about “cleansing” and “detoxing”

The word “detox” has a kernel of truth, just not the one being advertised. In its 2018 overview, the German Nutrition Society (DGE) writes: “A healthy human body can ‘cleanse’ itself by eliminating unwanted substances through the liver, kidneys, intestines, skin, and respiration.” The process exists. It just does not need a product.

The most common objection is: “Everyone talks about toxins, and you say they don’t exist?” There is a more honest answer. None of the sources reviewed for this article uses the term “toxins” at all - neither the DGE, nor IQWiG, nor the gastroenterology professional association. Anyone promoting products this way is using a word that does not appear in professional terminology.

This is not an aside from a single voice, but the assessment of a professional association. And it does not say that cleanses must be harmful. It says that the claimed effect has not been proven in studies. The difference matters if you are standing in front of a store shelf right now.

What experts mean when they say bowel cleansing

In medicine, “bowel cleansing” is a defined procedure with a clear purpose. In 2023, the German Society for Gastroenterology, Digestive and Metabolic Diseases, Endoscopy and Proctology wrote: “Thorough bowel cleansing is necessary to prepare for an examination (e.g., a colonoscopy or surgery).” It is therefore a means of enabling the examiner to see anything at all. It is not a health goal.

How medical bowel evacuation works

According to the same source, the substances used are “PEG-based substances (polyethylene glycol solutions)” and “saline laxatives (osmotic laxatives).” PEG stands for polyethylene glycol, also known as macrogol; saline products are salt solutions. Both are laxatives; the source says nothing more about them.

That is why it also says, “Without enough fluid, the bowel cannot be cleaned properly.” The process “usually begins the day before the examination,” and the goal is described precisely: bowel cleansing is successful “when the stool is liquid, light-colored, and clear like chamomile tea before the examination.” This describes a condition for an endoscopy, an examination using a camera inside the bowel, not a promise of well-being.

Someone who enters “bowel evacuation” into a search engine lands on this medical procedure and reads it as instructions for home use. That is where the confusion begins.

What purging costs the body

Any product that makes stools watery comes at the same cost. In 2023, IQWiG described it in connection with diarrhea: “Anyone with diarrhea loses fluid and electrolytes. That is why the most important thing is to replace this loss.” Electrolytes are dissolved salts such as sodium and potassium.

This explains why medical bowel cleansing is explicitly tied to fluid intake and takes place as preparation for an examination. Anyone who creates the same effect at home without this framework faces the same risk without the same supervision.

These warning signs are meant to prepare you for a conversation, not for self-diagnosis. They tell you when to leave the matter to a professional.

Four things that can be called bowel cleansing

The same two words refer to very different processes. The table sets them side by side and explains what each is based on. Where the sources reviewed for this article offer no evidence, that is stated rather than filled in with a guess.

If you want to choose between options rather than clarify the term, the article on gut restoration may help. It discusses rebuilding after a strain, not promises of cleansing.

Why a cleanse can still feel good

People who have done a cleanse sometimes report feeling better afterward. That should be taken seriously, and it doesn’t contradict the research. The DGE gives the most likely explanation for the visible part of the success: “The rapid weight loss is very likely due solely to energy restriction.” Energy restriction simply means that significantly fewer calories enter the body during this period.

And the scales show something different from what was hoped for. According to the same source, the short-term success is “primarily due to a loss of water, not body fat.” In essence, according to the DGE overview, a very low calorie intake also lowers the basal metabolic rate, which encourages the yo-yo effect after the cleanse ends.

Then there’s the part no study measures: when people eat and drink mindfully for a few days, they pay attention to their bodies. That attention doesn’t disappear just because the product doesn’t work. It’s simply possible to have that experience without a product. If you came here expecting to lose weight, you’ll find the longer version in the article on gut cleanses and weight loss.

This is the obvious objection: “If it helped me, I don’t care what the studies say.” Understandable. But you’re paying for the part that works precisely the price of the part that hasn’t been proven.

Common and established: three statements in a fact check

These statements appear in similar or identical form in marketing copy and conversations. None of them is stupid. Each can be checked against a source.

Fact check

If you want to know what “flora” and “microbiome” actually mean, you’ll find the basics in the article What is the microbiome?.

When building up your gut has a clear purpose

Not every interest in the gut microbiome is a marketing claim. There are situations with a clear reason for it, and the strongest is the period after antibiotic treatment. For more on how to think about this, see the article Building up your gut microbiome after antibiotics.

The difference from a cleansing cleanse is the direction. The cleanse aims to get something out. Building it up aims to let something in, and takes time rather than a cleanse on an empty stomach.

Your gut cleans itself every day. The question is what you give it—and no cleanse product answers that question; what matters is what regularly ends up on your plate.

What a gut microbiome test shows before and after a cleanse

Here comes the second objection, and it’s a valid one: “If cleanses don’t do anything, then your test doesn’t either.” The honest answer is that these are two different things. A mybody®x (MYBODY Lab GmbH) gut microbiome test doesn’t measure effectiveness. It describes a state at the time you take the sample.

It shows the composition of the gut flora: bacterial groups, pH value, and fungal colonization. The pH value indicates how acidic or alkaline the intestinal contents are. Fungal colonization refers to the extent to which yeast can be detected in the sample. We deliberately don’t include more than these three details here because the full list of parameters has not been approved.

Before a cleanse, a result like this provides a baseline; afterward, it provides a point of comparison. What it is not is just as important to make clear: It does not evaluate a cleanse, measure toxins, or make a diagnosis. The article on diversity in microbiome results explains how to read such a result; the comparison of tests related to a gut cleanse explains which tests may be relevant in connection with a cleanse.

What you can do now

If you came here wondering which cleanse is right, this text hasn’t answered that question—because the sources reviewed don’t answer it. What it does answer is the question that comes before it: Which process do you actually mean when you say “colon cleanse”?

Before a colonoscopy, the clinic specifies the procedure, which involves drinking fluids. Symptoms that persist for weeks should be discussed with a medical professional; the warning signs above tell you when it’s urgent. And if you want to understand your own condition, a sample from everyday life can provide one data point.

It all started with the word “cleanse.” And that’s actually true—only the body does it itself, and it’s already doing it today.

Frequently asked questions

Sources

1. German Nutrition Society: Detox diets, DGEinfo 3/2018 (as of 2018) – dge.de
2. German Society for Gastroenterology, Digestive and Metabolic Diseases, Endoscopy and Proctology: Bowel cleansing (as of 2023) – dasgastroenterologieportal.de
3. IQWiG, gesundheitsinformation.de: How does the intestine work? (as of 2026) – gesundheitsinformation.de
4. IQWiG, gesundheitsinformation.de: Diarrhea (as of 2023) – gesundheitsinformation.de

All statements about detox diets, the body's self-cleansing, and weight loss are based on [1]. The process and purpose of medical bowel cleansing are from [2], information about the large intestine is from [3], and the threshold for diarrhea and the loss of fluids and electrolytes are from [4]. Product information comes from mybody®x product pages and was checked on 09.09.2026.