Last night I watched the movie Fat, Sick, and Nearly Dead. The movie followed two unhealthy people who suffered from a chronic disease on their juice fasts and subsequent lifestyle changes. Their health improved dramatically, their disease was cured, and they both lost tons of weight.

Part of the goal of the movie seems to be to encourage the movie's viewers to go on a juice fast which they called a Reboot. The Reboot Juice Fast FAQ on the movie's website makes a bunch of vague claims about cleansing and toxins, but the claim I'm most interested in is stated in the first question:

Can I live with no protein for the duration?

When we cleanse, the main goal is to unravel and release as much toxic burden from the body as possible. In fact, most of us have undigested proteins stuck in our tissues and cells from years of ingesting certain foods. In terms of protein, what we are really looking for are the amino acids, or building blocks of protein which reside in everything: green leafy vegetables, fruit, sprouts, other vegetables, nuts, seeds, coconut, avocado, whole grains, beans, legumes. So even when you are not cleansing, it is virtually impossible to become protein deficient. However, while on the cleanse, we do not need to concern ourselves with this aspect, as again we really want to unload the undigested proteins which are sitting in the system.

Having undigested protein from "certain foods" (which foods?) doesn't seem to fit what I know about human biology.

So, do most (or at least some) humans have undigested protein in their bodies?

  • 27
    sounds like all the other "detox" scam products.
    – jwenting
    Nov 16, 2011 at 11:03
  • 5
    Information about detoxification schemes and scams (with 7 credible journal references): quackwatch.org/01QuackeryRelatedTopics/detox_overview.html Nov 17, 2011 at 3:44
  • 6
    “Undigested proteins”? Of course, otherwise our body can’t function! After all, proteins are the cells’ machines. But from ingested food? Not likely; and even if, then only in trace amounts. Source: any biology textbook. Where, according to the authors of the claim, do these undigested proteins go, by the way? In the colon? In the ECM? Inside cells? Uh … Nov 26, 2011 at 20:43
  • 1
    to clarify further: of course there's undigested protein in your body, it's the protein that's not yet been digested since your last meal. But it won't stay there for years, usually it'll have been digested within a few hours at most (depending on the size of that meal).
    – jwenting
    Nov 29, 2011 at 6:36
  • 8
    This is a good example of why to use controlled studies for medical claims, rather than movies :) The unhealthy people really made two major changes - they started a juice fast and they changed their lifestyle. Either of which implies that they also stopped eating what could have been a very unhealthy diet, say with lots of sugary sodas, white flour, alcohol, etc. So it doesn't mean juice-fasting is healthy, so much as it's healthier than whatever they were doing before.
    – John C
    Nov 29, 2011 at 13:41

1 Answer 1



An "undigested protein stuck in our tissues and cells" implies that somehow untouched proteins (polymer chains made of amino acids linked together by peptide bonds) get through the process of digestion unscathed and are absorbed into the bloodstream. This doesn't happen, and someone would have to have some very serious problems with their entire digestive tract if it did.

This thinkquest article outlines the process of protein digestion in quite a straightforward manner:

The process of digestion breaks down complex food molecules (such as the protein in steak) that the body cannot readily use into simpler, smaller molecules (amino acids) which the body can absorb and use to fuel other life processes. The digestive tract performs this mission like a machine. Each organ has a specific job and depends on the others to perform properly. In the mouth, initial physical break-down of protein begins. The stomach continues physical break-down and begins chemical break-down by secreting a substance called pepsinogen. It then converts pepsinogen into an enzyme called pepsin. This enzyme starts to break apart the protein into amino acids. Muscles in the stomach walls then move the food into the duodenum, the first part of the small intestine. The duodenum and pancreas work together to complete the chemical break-down of protein into single amino acid molecules with the help of another enzyme known as trypsin. Finally, the small intestine absorbs the amino acid molecules, allowing them to pass into the bloodstream. The blood then carries the amino acids to the rest of the body to rearrange into human proteins and use in building its structure. Each part of the "machine" of digestion must work properly in order for protein to be broken down into useful amino acids.

So, for someone to have undigested protein in their tissues and cells, their stomach, pancreas and small intestine would all have to be functioning very, very abnormally.

  • 2
    Viruses can create foreign proteins which are released locally.
    – HappySpoon
    Jul 9, 2014 at 5:08
  • 3
    Disappointing. The "pounds of rotting food and toxic sludge" reference was the only thing I liked about the Nu-biotics radio commercial. Apr 4, 2017 at 14:06

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