The elemental diet (ED) is partially defined as something “fundamental,” “simple,” and “uncomplicated.” Indeed, the term “elemental diet” nearly describes the thing – a “chemically defined” medical food composed of breakdown products of protein, carbohydrates, and fats, along with essential vitamins and minerals, delivered to the patient through a nasogastric tube in a hospital (or home) setting, or as a liquid beverage, much like a meal replacement or cleansing product.
What distinguishes an ED from typical meal replacement is its defining feature: pure, free-form amino acids, devoid of the whole proteins of polymeric feeds or the small peptides of a semi-elemental diet. These amino acids are joined by a carbohydrate component consisting of monomers of glucose, dextrose, or the very weak oligosaccharide, maltodextrin. High sugar content is required to meet the energy requirements of the exclusive nutrition the ED provides in most therapeutic regimens. The fats are commonly in the form of medium-chain triglycerides, combining stability and bioavailability. Fat content is minimal in most of these products, given the role of high-fat diets in the pathogenesis of IBD. Finally, vitamins and minerals are included, in amounts that meet RDA requirements.
The ED’s strengths derive from its unique properties: high nutritional efficacy, largely monomeric composition, proximal digestibility (ie, “pre-digested”), low residue, hypoallergenicity, and water solubility.12 The diet is also flexible and modifiable.
The elemental diets are coupled with therapeutic whole-food diets, relapse rates improve (as they do with the use of partial or half-EDs). In an uncontrolled IBD study, an individualized exclusion diet was examined that allowed 51 of 77 patients to remain well on diet alone for periods of up to 51 months, with an average relapse rate of less than 10%.51 And in a large multi-center, controlled trial, a 2-year probability of relapse was lower in a group treated with with EDs followed by excluded foods (commonly dairy products, cereals, and yeasts).52
In IBS, where diet has clearly been identified as an important etiological factor, the response rate to elimination diets ranges from 15-71% (with the highest response rates in cases of diarrhea-predominant IBS).53
SIBO-literate physicians treating IBS generally agree that dietary therapy is required after SIBO is eradicated, whether by pharmaceutical or herbal antibiotics, or by an ED. Clearly, it is just as important to follow an ED used to induce remission in IBS as it is in IBD, but there is no general agreement on precisely what dietary therapy is needed in either condition.
I strongly urge initiation of individualized diets incorporating elements from the Specific Carbohydrate Diet (SCD) and the Low-FODMAPS Diet (LFD). These evidence-based therapeutic templates have been successfully embraced by many physicians and patients, and have small studies supporting them in both IBD54 and IBS.55 Additionally, a Semi-Vegetarian Diet (SVD) has been studied and shown to be “highly effective in preventing relapse of CD.”56 It is beyond the scope of this article to address the particulars of manipulating these therapeutic diets in IBS and IBD, as each requires study to appropriately construct regimens to follow an exclusive ED or to accompany a partial ED.