Cleansing Diets: Why or Why Not?

Cleansing diets are trendier than ever. But do they actually provide any of the claimed benefits?

by Brian Dunning

Filed under Consumer Ripoffs, Fads, Health

Skeptoid #335
November 6, 2012
Podcast transcript | Listen | Subscribe
Also available in French | Russian

These days, just about everyone has some friend who is doing a "cleanse". Cleansing is the process of severely limiting your intake of food for some period of time, usually around five days or so, often replacing food with a fruit drink. Believers in cleansing consider it to provide a whole long list of health benefits; however, doctors never seem to prescribe it for anyone. There are, in fact, two schools of thought on the matter. On one side you have the alternative health marketers, nutritionists, naturopaths, chiropractors, and other alternative medicine providers who sell cleansing drinks or books; and on the other side you have doctors and dietitians who never mention cleansing to anyone at all. Unfortunately, right in the middle are all of us, the consumers who have to make decisions based on what we hear. What should we conclude about cleansing?

Even the Big Pharma conspiracy theory has a place in cleansing. Some advocates believe that the reason doctors don't prescribe cleanses is because it's not a drug they can make money on. Like most conspiracy theories, this one is patently absurd: the majority of what doctors tell patients is good basic health advice on which they don't make a dime; and there is a tremendous amount of money to be made selling cleansing products. In 2011, Businessweek reported that Marketdata Enterprises found boutique cleansing juices to be a $60 billion industry.

The difference between a nutritionist and a dietitian is an important one. In most countries, a dietitian has an accredited degree and is a licensed professional, while nutritionists are not subject to any regulation or training requirements, and are really just any person who chooses to call themselves that. Generally, dietitians practice science based medicine, and nutritionists are usually part of the alternative medicine community.

So without the advice of a medical professional, what person would stop eating a healthy diet in favor of an expensive fruit drink? According to BluePrint, one of the most upscale and expensive cleansing drinks, the majority of its customers are healthy, educated young women. BluePrint and other marketers are notoriously unclear about the benefits of their product, using only vague, medically meaningless terms like "cleansing impurities" and "restoring balance". I visited a large number of alternative health and cleansing websites to see if anyone made specific claims about why someone should do this. I did find a number of common themes. Let take a look at these claimed benefits of cleansing, one by one.

1. Lose weight.

A cleanse is basically a fast, and obviously, fasting of every type results in weight loss. Whether you consume nothing at all, just water, or otherwise reduce your intake to fewer calories than your body requires, your body must dip into its energy stores. A regular healthy diet for the average person delivers around 2,500 daily calories, and if you cut that by 80% and replace it with a half liter or so of high-sugar fruit drink, you've got a big deficit. And a deficit that size causes your body to turn to its protein stores — your muscles — in addition to your fat. What you're losing is lean mass, not fat mass.

A far healthier (and safer) way to lose weight, that's more likely to deliver long-term results, is to get regular exercise and reduce your daily intake to a balanced diet of just your basic requirement — called the basal metabolic rate — or even just below it, and stick to it.

2. Rid the body of toxins.

The central thesis of cleansing is that our bodies are all choked with toxins, and that the special cleansing diet will solve this. It's most telling that almost none of these companies ever tell you what these alleged "toxins" are — if they did, it would be a trivial matter to verify through simple before and after blood tests.

Some marketers do mention specific substances like lead, mercury, asbestos, etc. Very few people actually have harmful levels of these; and for those who do, it's a serious medical condition for which medical interventions do exist. Starving yourself is not among them. There is no plausible biochemical reason why a fast would impact heavy metal levels, despite the unfounded assertions made by those who sell them.

Most often, cleansing marketers imply that normal dietary intake constitutes toxins, often enhancing their rhetoric with scare words like "processed" food, "chemicals", "biotech" crops, and so on. Fasting will certainly empty your digestive tract, whether you drink water, special $100/day fruit juice, or nothing at all. But anything you've already eaten, that's already been metabolized, would certainly not be affected.

It's fair to ask how people have survived so well when only a very few people in wealthy countries have picked up on this trend, and only in recent years. The reason is that the human body already has a 100% proven method of detoxifying itself. In medical terms, it's called pee and poop. The processes that create pee and poop and expel them from the body operate independently of whether you buy cleansing drinks. The consumption of cleansing drinks does not create new detoxifying methods, so their use for this purpose is fundamentally uninformed.

Moreover, fasting depletes your liver's store of glutathione, an antioxidant that's one of the most important substances used in the detoxification of blood. This depletion, and resultant decreased liver function, actually causes waste products to accumulate in your body, exactly the opposite of what the advertisers claim for their products.

3. Strengthen the immune system.

This claim asserts that your immune system is weakened by your normal diet, and is thus strengthened by the cessation of food intake; and also that the contents of the cleansing drink include special nutrients that "boost" your immune system.

As we discussed in great detail in the Skeptoid episode about immune system boosting, the entire premise is wrong. There's only one component of the fantastically large and complex immune system that can be strengthened, and that's the part called the adaptive immune system: the various types of T-cells and B-cells whose production is triggered by a response to a disease agent. Catch a cold, and your adaptive immune system develops new killer cells adapted to the surface proteins of that particular pathogen. These cells cannot be created by drinking a special juice; they can only be created by challenging the body with exposure to a disease.

Knowing this, the marketers of cleanses generally contend that your immune system is compromised because of your normal diet, again trotting out the scare words like "processed" food, "chemicals", and "biotech" crops, therefore our bodies are contaminated. It sounds like it makes sense. People do overeat, we love our prepared foods, and many of us are obese. Has this truly resulted in compromised immune systems?

In fact, the opposite is true. Obese people generally have inflammation, which is an immune response. We catch colds and have no difficulty in producing symptoms. When we're exposed to irritating substances, we react with hives or itching or asthma, all of which are immune responses. Practically every one of us has some immune system response going on right now. The claim that living in our modern world has compromised our immune systems is measurably, and unambiguously, untrue.

4. Cure a variety of illnesses.

Similar claims are made that our normal diets are the cause of a huge number of diseases, and that replacing those diets with expensive juice for a few days is all it takes to make the diseases all go away.

I found a staggering number of such conditions claimed on the web sites. Here's a partial list in alphabetic order: abnormal sugar levels, acne, addiction, aging, allergies, anxiety, bad breath, bloating, cancer, cell damage, contamination with chemicals, depression, diabetes, fatigue, headaches, heavy metal contamination, hormone disfunction, indigestion, lack of focus, liver disease, liver stones, memory loss, obesity, thyroid disease, the list goes on; and of course, that "Modern lifestyle has taken its toll on our organs." Imagine, all of these, treated by the same wonder cleanse.

Unless you subscribe to the conspiracy that all medical institutions, professionals, and students worldwide are being paid to suppress this miracle, you might wonder why doctors don't treat any of the above with cleansing diets. The reason is simply that it's untrue. As much as we'd all love for there to be miraculously easy solutions to complicated problems, it's rarely the case. The first red flag is that the marketers claim to successfully treat so many conditions with a single miracle product. The second red flag is that it's a high-end, boutique, expensive product marketed to the people who can afford it. Red flags don't prove anything on their own, of course, but they should give you pause to be skeptical.

5. Increase your energy.

In fact, the opposite is true. Severe calorie deprivation causes your metabolism to slow dramatically as your body attempts to conserve its limited biochemical resources. Among the most noticeable results of fasting are lethargy, weakness, even fainting, as anyone who has tried it has experienced. When your blood loses its nutrient supply that usually comes in through your digestive system, it has to shift to breaking down the fat stores, a process called glycolysis, which is a much less efficient process.

Most cleansing drinks try to combat this inevitable lethargy by containing almost exclusively sugar, the most bountiful nutrient in fruits. This gives your body a temporary boost, but as simple sugar is metabolized very quickly and there's little else in those precious few hundred daily calories from the drink, your body is soon left high and dry.

6. Increase your brain function.

Again, the opposite is true. Your brain runs primarily on sugars. Cutting your caloric intake by 80% or more means that there's no incoming fuel. Your liver stores enough of the polysaccharide glycogen to fuel your brain with glucose for about 6-12 hours. Halfway into the first day of your cleanse, that store is gone, and your body starts breaking down its own tissues for glucose to keep that all-important brain going. Your brain slows down many non-essential functions, and the result is that within just the first day of fasting, your attention and responsiveness begin to drop. Fasting is not good for the brain.

Tip Skeptoid $2/mo $5/mo $10/mo One time

7. It's inexpensive.

I'm constantly floored by the claims of alternative health products, such as cleanses, that characterize their products to be a blow at greedy corporate pharmaceutical interests. With boutique cleanses alone being a $60 billion industry, imagine the size of the overall alternative health industry. With every cleansing purchase, a customer is enriching an already extremely wealthy corporate culture, and no amount of greenwashed, all-natural, organic purity inspired product marketing, nor even celebrity endorsements, can change that fact.

Some of the marketing asserts that by not buying food for a few days, you're saving money. That might be true, but cleansing products are rarely inexpensive; and often their prices alone are competitive with, or exceed, the costs of a healthy home-cooked daily diet.


Almost everyone's diet could stand some improvement. Doing so is a conscious, ongoing commitment. Some of those who are too lazy, or too busy, or have some other excuse, try to shortcut the hard part by instead throwing a few dollars at a miracle product, and then returning to their lazy ways. Cleansing diets simply do not work. At best they accomplish nothing besides transferring money from your pocket into the pockets of the advertisers, and at the worst extreme they can damage virtually every part of your body.

Cleansing is a made-up solution. It is not a substitute for good diet and exercise. It is a for-profit ripoff, invented by those who think they can easily take your money by cloaking their claims in positive, healthy-sounding rhetoric. Clever marketing and implausibly high prices are always a sign that you should be skeptical.

Brian Dunning

© 2012 Skeptoid Media Copyright information

References & Further Reading

Editors. "Nothing Tastes as Good as Skinny Feels." Bloomberg Businessweek. Bloomberg LP, 18 Feb. 2011. Web. 2 Nov. 2012. <>

Editors. "How Glycolysis Works." Anatomy & Physiology. McGraw-Hill Companies, 4 Nov. 2008. Web. 2 Nov. 2012. <>

Miller, B. "How Crash Diets, Like the Master Cleanse, Harm Your Health and Heart." Health. Health Media Ventures, 22 Jun. 2009. Web. 3 Nov. 2012. <,,20409933_1,00.html>

Moore, S. "Health Risks of the Master Cleanse Diet." Livestrong. Demand Media, 26 Apr. 2011. Web. 3 Nov. 2012. <>

Moores, S. "Experts Warn of Detox Diet Dangers." NBC News., 18 May 2007. Web. 3 Nov. 2012. <>

Wohaieb, S., Godin, D. "Starvation-Related Alterations in Free Radical Tissue Defense Mechanisms in Rats." Diabetes. 1 Feb. 1987, Volume 36, Number 2: 169-173.

Reference this article:
Dunning, B. "Cleansing Diets: Why or Why Not?" Skeptoid Podcast. Skeptoid Media, 6 Nov 2012. Web. 9 Oct 2015. <>


10 most recent comments | Show all 75 comments

Guys, the superfood issue keeps raising its ugly head in these comments section.

Some foods and juices are just a wonderful treat from time to time. The fact that some folk worship their time with something a little more expensive shows some taste "eclecticism".

Justifying that your treat will save you from a dread disease, immunise you from cancers general and possibly make you more charming to the preferred sexual partner only exemplifies that anyone will justify anything.

Hypochondria is a bit like that.

Its a great party starter to criticise product labelling and inherent parent woo (my term, use at will).

we are lucky to live to the odd seventy-eighty our generation and hopefully 90-100 for our kids.

Enjoy your treats wisely. No, your ultra dark, fair trade organic chocolate bar with extra crispy blattodea flecks will not prevent you from getting cancer.

Come to think of it, who would dare tell someone with a life threatening disease to just eat their favorite woo food to a cure?!

Only a munchausens specialist.

Moral Dolphin Back in Mud Suit, Greenacres by the sea Oz
June 4, 2013 11:13pm

Man I'm not going to fast anymore because of this article . I had done a few 24 hour fasts, and always felt pretty good during the fast really. I heard it was good to come out of the fast on some vegetable juice but I sometimes just went for a normal meal. During the fast I felt like my brain totally sped up and felt an increase in clarity neither of which felt like placebo. But some of my later ones I would do stupid stuff like go play basketball. One day I worked out in a gym and played basketball, then the next day I was out smoking a cigarette on the porch and I felt woozy, so I went inside and immediately fainted. I fell backwards and the back of my noggin bounced off the floor. Then for like a half hour I had cold sweats and my friend said my face was pale. Yeah I'm just going to stick to a normal diet from now on. I'm all about the pimp tight salads tho. I make mean salads YUH!

Sam Waters, In the mouth of Madness
October 4, 2013 11:33pm

People in the western world do not live far longer than ever before.

The increase in life expectancy has been that from birth, and it has increased because of reduced infant and child mortality.

An adult's life expectancy has not changed significantly in a long time (centuries?, millenia?); I think there has been a slight increase in the last few years.

Chris, Toronto
October 12, 2013 12:50pm

Li Ching-Yuen was a Chinese herbalist that supposedly lived to be over 256 years old. He worked as a herbalist, selling lingzhi, goji berry and wild ginseng...

Mike Di Vito, New York
October 12, 2013 1:50pm

I couldn't laugh through this article because Dunning clearly knows nothing about what he is writing...........sad, very sad. I recommend he watch "Fat, sick and nearly dead".

Jackie, Canada
December 17, 2013 6:44pm

Chris in Toronto -

You're precisely wrong. Nearly all of the increase in life expectancy in the late 20th and early 21st century has been due to a decline in late-life mortality.

Paul M.A., Humboldt, CA
January 20, 2014 10:23pm

This article is pure FUD, but so is the "cleanse" industry. There are real benefits to a proper cleanse that includes fasting. Fasting is not about reducing calorie intake, it's about letting your body AND mind rest from *everything*.

I wonder if this is how valuable ancient knowledge gets "lost".

Ivan V., PDC, Mexico
January 27, 2014 12:44pm

Yes Ivan, skepticism is exactly how "valuable" ancient "knowledge" gets lost.

Andy, Melbourne
June 10, 2014 1:06pm

Yeah, you immediately lost all credibility when you referred to feces and urine as "pee and poop".

~~~, Your mom's chest hair
July 29, 2014 4:08pm

Hi, I'm late to the conversation, but:
Although the article contains many good points that the touted benefits of cleansing don't have science and expert opinion behind them in most cases, I'd like to ask one thing and make a comment:

Q: Are there studies on cleansing/fasting that rigorously disprove the many claims?

Comment: I think some conclusions here might go a bit far. Case in point: fasting is not good for the brain. While it is true that the brain needs energy, and fasting deprives it of energy, this may not be the whole story. It is the case that some systems benefit from a limited amount of stress. For example, bones deteriorate in the absence of the stress of gravity. Furthermore, there was (after this article) a study suggesting that fasting can reduce the chance of Alzheimer's (

STL Tim, St. Louis
December 29, 2014 5:50pm

Make a comment about this episode of Skeptoid (please try to keep it brief & to the point).

Post a reply


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