A juice cleanse sounds like an awesome way to kick off that diet many people plan on doing. For several days, the body only receives fruits and vegetables, allowing the body to rid itself of unwanted toxins and byproducts from food and the environment. The only disadvantage is, that it is not exactly how the body actually works.
Maybe this has happened to you: You invite your friends to lunch and they politely decline, saying they are on a cleanse. Turns out they drink nothing but juice for the next 3 days because they want to give their digestive system a kind of reset. There are even juice cleansers programmes out there. The basic idea is: you pay a certain amount per day, and you are provided with sets of juices to consume in some particular order. For the next few days, from 3 to up to 10 days, you drink only juice all the time, without consuming solid food. If you are lucky you consume 1200 calories per day, but usually its less. Different programmes promise different benefits, but most of them promote the same thing: a juice cleanse will clear out your toxins and reset your digestive system, or they often say that the programme will help you lose weight quickly. None of these things are actually based on science.
The definition of toxin refers to it as a kind of poison produced biologically. And your body does produce harmful by-products as ammonia, which ends up in your urine, but that is the thing: it ends up in your urine because it’s filtered out, first by your liver and eventually by your kidneys. Your body has built-in mechanisms to get rid of the bad stuff. Drinking only a juice for few days will not make your liver or kidney work better and faster. Those organs are supposed to do that anyways, otherwise you are suffering from kidney failure.
This juice cleanse programmes also present another image, that there is all these extra gunk stuck to the sides of your intestines and the best way to get rid of it, is to give yourself diarrhea for a few days and maybe finish that off with water. But the human plumbing system doesn’t work like the one you find in an old house. Instead, waste is constantly moving through a healthy digestive system. Food normally takes 24 to 72 hours to be completely digested by your body, there is nothing left on your intestines from the burger you ate last year. Your body absorbs whatever it can and the rest comes out, it doesn’t get stuck to the walls all along the way.
What about the weight loss? People who do juice cleanse almost always lose weight, but most of it is in the form of water weight. But despite what it sounds like, this water weight is not just the weight you lose by peeing a bunch of water, it actually comes from Glycogen in your muscles. Glycogen is a form of stored sugar that your body uses when it’s running low on energy, like when its getting way fewer calories than usual, all in form of a juice. As soon as you start eating normally again, your body will replace this glycogen and you will bounce back to wherever you were.
On the other hand, for most healthy people, a juice cleanse probably won’t hurt them. They won’t be getting all the calories and nutrients their body needs, but most of these programmes aren’t long enough to do some long-term damage.
So if you want to drink nothing but juice, you will be fine, but you won’t be detoxifying or rebooting anything, you will be just drinking a lot of, usually expensive, juices.