What is the difference between polymeric and elemental feeds?

November 15, 2025 •

3 min read

Individuals with IBS and SIBO have shown a 66% reduction in symptoms after 14-21 days of an elemental diet. The primary distinction between polymeric and elemental feeds lies in the breakdown of nutrient components, especially protein, affecting their use in different clinical scenarios.

Quick Summary

Polymeric feeds use intact proteins, suitable for normal gut function, whereas elemental feeds use pre-digested nutrients like amino acids for easy absorption in compromised systems. They differ significantly in composition, cost, and patient tolerance.

Key Points

Nutrient Form: Polymeric feeds use whole, intact proteins; elemental feeds use pre-digested nutrients like free amino acids.
Digestive Function: Elemental formulas are for compromised digestive systems; polymeric formulas suit those with near-normal gut function.
Cost and Palatability: Elemental feeds are more expensive and less palatable than polymeric formulas, often requiring tube feeding.
Clinical Application: Elemental diets are used for Crohn's disease flares or SIBO, while polymeric feeds are used for general nutritional support.
Absorption Speed: Elemental feeds are rapidly absorbed in the upper gut; polymeric feeds require full digestion, absorbing over a longer period.
Medical Supervision: Both enteral nutrition types require medical oversight for appropriate formula selection.

A Tale of Two Diets: Polymeric vs. Elemental Feeds

Polymeric and elemental feeds are both forms of enteral nutrition, supplying essential nutrients via the gastrointestinal tract, often through a feeding tube. The fundamental difference is how readily nutrients are available for absorption. Understanding this distinction is crucial, as the wrong formula can be ineffective or poorly tolerated. While polymeric formulas are similar to a conventional meal, elemental formulas are the dietary equivalent of a pre-digested meal, optimized for quick and effortless absorption in sensitive digestive systems.

What are Polymeric Feeds?

Polymeric feeds are the most common enteral formula, designed for patients with a functional digestive system. They contain macronutrients—protein, carbohydrates, and fats—in their complex, intact form, similar to regular food. These feeds require digestive enzymes to break them down into smaller, absorbable components. They are often less expensive and can be taken over longer periods. A key aspect of polymeric feeds is their palatability, with many formulas designed for oral consumption in addition to tube feeding.

Common characteristics of polymeric feeds:

Contain whole, intact proteins, carbohydrates, and fats.
Lower cost compared to more specialized formulas.
Typically contain fiber and are lactose-free.
Suitable for patients with near-normal gut function.
Examples include Ensure and Jevity.

What are Elemental Feeds?

Elemental feeds, also known as free amino acid-based formulas, consist of macronutrients that have already been broken down into their simplest forms. Protein is present as free amino acids, carbohydrates as simple sugars, and fats as medium-chain triglycerides. This "pre-digested" state means they require minimal to no digestion and are rapidly absorbed in the upper gastrointestinal tract. This makes them ideal for patients with significant malabsorption issues, digestive tract inflammation, or a need for bowel rest. The trade-offs include a higher cost, poor palatability, and a hyperosmolar load, which can cause side effects like diarrhea.

Common characteristics of elemental feeds:

Nutrients are in their simplest, most basic form (amino acids, simple sugars).
Higher cost due to advanced processing.
Often unpalatable, requiring administration via a feeding tube.
Rapidly absorbed, allowing for bowel rest.
Used for severe malabsorption conditions like Crohn's disease and SIBO.
Examples include Vivonex and Glutasorb.

The Key Differences at a Glance


Feature	Polymeric Feeds	Elemental Feeds
Protein Source	Intact, whole proteins	Free amino acids
Digestion Required	Full digestion by the gut is necessary	Minimal to no digestion required
Absorption	Primarily absorbed in the small intestine	Rapidly absorbed in the upper small intestine
Gut Function	Suitable for normal to mildly impaired gut function	Designed for severely impaired gut function and malabsorption
Cost	Less expensive	Significantly more expensive
Tolerance	Generally well-tolerated and palatable for oral use	Often poorly palatable, can cause side effects like diarrhea due to high osmolarity
Common Use Cases	General nutritional support, malnutrition, maintenance	Crohn's disease flare-ups, short bowel syndrome, severe malabsorption, SIBO

Selecting the Right Feed for the Patient

Choosing between a polymeric and elemental formula depends heavily on the patient's underlying condition and digestive capabilities. For most patients with adequate gut function, a polymeric formula is the standard and cost-effective choice. It provides complete nutrition and is easy to administer. In cases of severe intestinal inflammation, malabsorption, or compromised gut integrity—such as during an active Crohn's disease flare-up or severe pancreatitis—an elemental formula becomes the preferred option. The decision is always made under the supervision of a healthcare team, including a dietitian, who tailors the specific feed to meet the individual's unique nutritional requirements and clinical goals.

Conclusion

While both polymeric and elemental feeds provide vital nutritional support via enteral means, they differ in their composition and intended use. Polymeric feeds, with their intact macronutrients, are the standard for patients with normal gut function, offering a more cost-effective and palatable solution. Elemental feeds, containing pre-digested nutrients, are a more specialized and expensive option reserved for those with compromised digestive systems who require minimal digestion and rapid absorption. The appropriate choice hinges on a thorough clinical assessment to ensure the most effective and tolerated nutritional therapy is delivered.

Crohn's & Colitis Foundation: Nutritional Therapy for Crohn's Disease

Frequently Asked Questions

For active Crohn's disease, elemental feed is often preferred because its pre-digested nutrients allow bowel rest and healing by minimizing digestive work. A polymeric feed might be suitable in remission or for general support.

Switching between feed types should always be done under a doctor's supervision. The transition depends on clinical needs, digestive tolerance, and the reason for the initial feed.

Elemental feeds are often unpalatable due to their amino acid composition. They are often administered via a feeding tube, though flavored versions are available for oral use.

No, semi-elemental (or peptide-based) feeds are a middle ground. They contain protein as small peptides rather than whole proteins (polymeric) or free amino acids (elemental). They are more easily absorbed than polymeric but still require some digestion.

A patient with severe malabsorption given a polymeric feed may not digest and absorb nutrients properly. This can lead to diarrhea, cramping, and inadequate nutrition.

Elemental feeds are considered hypoallergenic because they use free amino acids instead of whole proteins, which are more likely to trigger an immune or allergic reaction. Polymeric formulas contain intact proteins and are therefore not hypoallergenic.

Elemental diets are not intended for weight loss and should not be used for that purpose. They are medically prescribed for specific health conditions, and use without medical supervision is not recommended.