As elemental diets grow in popularity – especially for use with SIBO – I’ve received a few emails from people (and doctors) suggesting that Absorb Plus (Original formula) is not actually an elemental diet product. And that only products with free-form amino acids as their protein source qualify as “elemental”. So what’s the difference between Elemental vs. Semi-Elemental diets?

Well let’s take a walk through the med literature and I’ll also share my own experience with elemental diets and various protein sources. Back when I first formulated Absorb Plus ORIGINAL (in 1998), whey protein isolate was considered one of the best protein sources for an elemental diet. And at the time, the clinical studies on “elemental diets” varied between using free form amino acids, whey isolate, whey concentrate, egg albumin, etc. and all were considered acceptable ingredients in an “elemental” shake.

However, I’ve conducted a review of the current med literature and it seems that the definitions are shifting, but as yet, are still not clear. Let’s walk through the pieces of this puzzle and let’s use Absorb Plus ORIGINAL as an example to give us a reference point to see just how the parameters are defined…

According to the Medical Dictionary:

Elemental Diet – contains nutrients as small molecular weight compounds, i.e. proteins as amino acids or peptides, carbohydrates as oligosaccharides or monosaccharides, and fats as medium-chain triglycerides. Used in the treatment of gastrointestinal disease. Called also monomeric diet.

So according to that definition, whey isolate or rice protein isolate (which Absorb Plus contains) would qualify as an “elemental” product since they are protein peptides.

However, according to this paper in 2005, Absorb Plus would be considered “semi-elemental/oligomeric/polymeric”:

The EN [elemental nutrition] formulas differ in their protein and fat content and can be classified as elemental (monomeric), semi-elemental (oligomeric), polymeric or specialized. Elemental formulas contain individual amino acids, glucose polymers, and are low fat with only about 2% to 3% of calories derived from long chain triglycerides (LCT) (3). Semi-elemental formulas contain peptides of varying chain length, simple sugars, glucose polymers or starch and fat, primarily as medium chain triglycerides (MCT) (3). Polymeric formulas contain intact proteins, complex carbohydrates and mainly LCTs (3). Specialized formulas contain biologically active substances or nutrients such as glutamine, arginine, nucleotides or essential fatty acids (Table 1). Although elemental and semi-elemental formulas cost about 400% more than polymeric formulas (4) they are still widely used because they are believed to be 1) better absorbed, 2) less allergenic, 3) better tolerated in patients with malabsorptive states and 4) cause less exocrine pancreatic stimulation in patients with pancreatitis.

In terms of taking this into the realm of practical application, I stand behind what I first discovered using elemental diets for myself and consequently wrote about in The IBD Remission Diet and that is that whilst free-form amino acids are considered more ‘hypo-allergenic’, they are not always best for inducing disease remission – because the person cannot gain weight and address malnutrition using only free-form aminos. This becomes especially important when dealing with children on an elemental diet, who need to make up for lost growth and height.

I searched high and low to find the answer as to why people would not gain weight ingesting only free-form amino acids as the protein source and finally learned why from a PhD in nutrition, who specialized in treating athletes: He said that the body will use free form amino acids more as a supplement (hormone pathways, mucosal lining, etc.), but it cannot use them to build muscle unless they piggy-back on a di-peptide (or higher) bond protein (like whey isolate). A really good paper that goes into this in detail is Protein digestion and amino acid and peptide absorption.

Yet more evidence that a semi-elemental diet is preferable to a strictly elemental diet is provided in numerous clinical trials, like this one with Crohn’s disease:

“A controlled trial was performed to compare enteral feeding with either an amino acid based feed or a whole protein feed as sole treatment for active Crohn’s disease.” In the group given the amino acid feed, 69% achieved remission within 3 weeks. In the whole protein feed, 72% achieved remission.

But the interesting thing was, when researchers then swapped the groups over onto the other diet – i.e. the amino acid group got switched to whole protein, and the whole protein group got switched to amino acids only – 43% in the group switched to amino acids relapsed, but NONE of the group switched to whole protein relapsed.

So, yes, Absorb Plus is an elemental shake product. However, when going on an exclusively elemental or bowel rest diet, you can choose whether to use a polymeric (semi-elemental) or monomeric (free-form amino acid) shake.

Current literature and many doctors today are calling polymeric formulas “semi-elemental”. But that does not take into account that back when many of the clinical trials were conducted on “elemental” diets, the definition included ALL versions of pre-digested proteins; monomeric, oligomeric, polymeric or peptides.

Absorb Plus at that time (yes, it’s been in production since 2002) was considered elemental and so can reference these clinical trial results for expected outcomes.

Now, just to make everything even crazier… here’s a clinical trial comparing semi-elemental vs. polymeric formulas. Say what? I thought we just established that semi-elemental/polymeric are the same thing? Well, not according to these scientists who compared Peptamen with Sondalis-Iso (both Nestlé products).

Except it gets even crazier, because they’re calling Peptamen a semi-elemental product – and it contains whey protein. And they’re calling Sondalis-Iso a polymeric product and it contains milk protein. So both these protein components are more complex/whole than Absorb Plus’ whey isolate (casein-free and lactose-free), and these products are also listed as “enteral nutrition” on Nestlé’s site; suitable for tube feeding.

All this confusion within the medical and clinical trial literature makes it very difficult for the consumer to draw conclusions on efficacy and which protein source to use when choosing an elemental, bowel rest product!

I can only speak from my own experience – having been on an exclusively elemental bowel rest diet three times during my healing journey from widespread Crohn’s (I’ve been 100% drug and surgery-free for over 20 years now). I found that free-form amino acid shakes were not helpful for two reasons: They didn’t taste very good (which is important when it’s your sole food source for 3-6 weeks) and I could not gain any healthy weight on them. However, I did extremely well on protein isolate (semi-elemental/polymeric) shakes – and my tried-and-tested formula became Absorb Plus ORIGINAL.

An elemental shake in Australia that fits these parameters is ElementGold.

I think that free-form amino acid formulas would work well for people using it mainly for allergy testing or clearance, or milder GI disorders like SIBO or IBS, or who do not need to gain weight (are not malnourished).

Vegan Elemental Shakes

Your other option, if you cannot tolerate whey protein isolate, is to use a vegan elemental shake. Absorb Plus VEGAN contains certified organic sprouted rice protein isolate, so is well tolerated by most people with dairy or protein allergies (rice is considered a well very tolerated protein source).

Hydrolyzed Whey Protein

In case you’re not confused enough already… there is yet another ambiguous term in play in the world of elemental diets: hydrolyzed whey protein, or, hydrolysates. Again, it is difficult to pin down a consistent definition of this substance – that is used consistently throughout the literature. Here are two definitions that are pretty similar, but again, one includes peptide proteins and the other only free form amino acids.

Protein Hydrolysatea sterile solution of amino acids and peptides prepared from a protein by acid or enzymatic hydrolysis and used intravenously for the maintenance of positive nitrogen balance in severe illness, after surgery of the alimentary tract, in the diets of infants allergic to milk, or as a high-protein dietary supplement.


Protein Hydrolysate – a mixture of amino acids prepared by splitting a protein with acid, alkali or enzyme. Such preparations provide the nutritive equivalent of the original material in the form of its constituent amino acids and are used in special diets or for patients unable to take the ordinary food proteins.

Sounds like protein hydrolysates would be highly tolerated and nicely hypo-allergenic if used in an elemental diet shake, right? But again, we have the same problem with it being difficult to build muscle from these formulas. And the other huge problem is that hydrolysates are incredibly bitter in flavor, thus difficult to ingest and usually paired with lots of synthetic, artificial flavoring agents to make them palatable. Many however, are just pumped in via a stomach shunt, or intravenously.

Extensive review of clinical trial literature

In conclusion, this comprehensive review of randomized controlled clinical trials, intervention studies, case studies and abstracts found that:

Results pertaining primarily to tolerance, digestion, and absorption were summarized for each patient population. The efficacy of semi-elemental whey hydrolyzed protein (WHP) diet have been reported in various nutritionally high risk patient populations including – Crohn’s disease, short bowel syndrome, acute and chronic pancreatitis, cerebral palsy, cystic fibrosis, cerebrovascular accidents, human immunodeficiency virus, critically ill, and geriatrics. Collectively, the evidence from the medical literature indicates that feeding with a semi-elemental diet performs as well or better than parenteral or amino acid based diets in terms of tolerance, digestion, and nutrient assimilation measures across various disease conditions.

*Note they have yet again combined three terms:

  • semi-elemental
  • whey
  • hydrolyzed protein

Let’s just leave it there!