What are the commonly used enteral formulas?

November 15, 2025 •

4 min read

Overwhelming evidence suggests that enteral nutrition (EN) is the best approach for nutrition in critically ill patients, and a functional GI tract is the principal indication for its use. Choosing the right product can be complex, and understanding what are the commonly used enteral formulas is the first step toward effective nutritional therapy.

Quick Summary

This guide breaks down the primary categories of enteral formulas, from standard diets for normal digestion to specialized and hydrolyzed options. It covers composition, indications, and key factors for formula selection.

Key Points

Standard Formulas: Polymeric formulas are the most common type, providing intact nutrients for patients with normal GI function.
Elemental Formulas: Containing pre-digested nutrients, elemental and semi-elemental formulas are designed for patients with compromised digestion or malabsorption issues.
Specialized Diets: Specific medical conditions, such as diabetes, kidney disease, or liver failure, may require specialized formulas with altered macronutrient profiles.
Blenderized Diets: Commercially or home-prepared, these formulas use real food ingredients and are an option for long-term feeding, especially for improved GI tolerance.
Individualized Care: The correct formula choice is based on a patient's clinical needs, GI tract function, fluid requirements, and metabolic state, highlighting the need for professional guidance.
Cost Considerations: It is important to note that specialized and elemental formulas are often more expensive than standard polymeric feeds.

Understanding the Landscape of Enteral Formulas

Enteral formulas are specialized liquid nutritional products designed to provide sustenance directly into the gastrointestinal tract, bypassing the need for oral intake. The wide range of available products can be broadly categorized into four main types: polymeric, elemental, specialized, and blenderized. The selection of an appropriate formula depends on a patient's medical condition, ability to digest and absorb nutrients, and specific nutritional requirements. A nutritional assessment, often conducted by a registered dietitian nutritionist (RDN), is a critical step in determining the most suitable formula.

Polymeric (Standard) Formulas

Polymeric formulas are the most commonly used type for patients with normal or near-normal digestive function. These formulas contain intact protein, complex carbohydrates, and fat, which require a functioning digestive system to be broken down and absorbed. They are nutritionally complete and designed to provide a balanced diet, making them the standard approach for most individuals requiring enteral nutrition support.

Key characteristics of polymeric formulas:

Intact Nutrients: Feature whole proteins like casein and soy, as well as complex carbohydrates such as corn maltodextrin.
Versatile Concentration: Available in various caloric densities, from 1.0 to 2.0 kcal/ml, allowing for adjustments based on patient energy needs and fluid restrictions.
Fiber Options: Many formulas contain fiber, which can promote healthy bowel function, while fiber-free options are also available for specific indications.

Elemental and Semi-Elemental (Peptide-Based) Formulas

For patients with impaired gastrointestinal function, such as malabsorption disorders, elemental and semi-elemental formulas are often necessary. These products contain macronutrients that are already broken down into their simpler components, requiring minimal digestion.

Comparison of elemental vs. semi-elemental formulas:

Elemental Formulas: The most basic form, with protein provided as free amino acids. These are used in cases of severe malabsorption or certain metabolic diseases.
Semi-Elemental Formulas: Feature protein in the form of small-chain peptides, which are more easily absorbed than intact proteins.
Fat Content: Often contain a high proportion of medium-chain triglycerides (MCTs), which are more easily absorbed without the need for bile salts.
Cost and Palatability: Both types are more expensive than polymeric formulas and typically have a less palatable taste, making them less suitable for oral supplementation.

Specialized (Disease-Specific) Formulas

Specialized formulas are created to meet the unique nutritional requirements of patients with specific disease states. These formulas modify the macronutrient profile to better address the metabolic demands of a particular condition.

Examples of specialized formulas:

Diabetes-Specific: Lower in carbohydrates and higher in fat and fiber to help manage blood glucose levels.
Renal-Specific: Calorically dense with adjusted protein, potassium, phosphorus, and fluid content for patients with kidney disease.
Immune-Modulating: Enriched with nutrients like arginine, glutamine, and omega-3 fatty acids, typically used in cases of metabolic stress, trauma, or surgery.
Hepatic-Specific: Designed for patients with liver disease, featuring a modified amino acid profile.

Blenderized Formulas

Blenderized tube feeding (BTF) formulas have gained popularity, especially for long-term home enteral nutrition, as they are made from real food ingredients. They can be either commercially prepared or homemade.

Considerations for blenderized formulas:

Commercial vs. Homemade: Commercially prepared BTF offers consistent viscosity and nutritional adequacy. Homemade versions require careful preparation and consultation with an RDN to ensure safety and completeness.
Improved Tolerance: Anecdotal evidence suggests BTF can improve GI tolerance and reduce symptoms like constipation or diarrhea.
Food Safety: Requires strict adherence to safe food handling practices to minimize the risk of foodborne illness.

Comparison of Common Enteral Formula Types


Feature	Polymeric (Standard)	Elemental / Semi-Elemental	Specialized (Disease-Specific)	Blenderized (BTF)
Nutrient Form	Intact whole nutrients (protein, fat, carb)	Pre-digested peptides and/or free amino acids	Varies; Modified macronutrient profile	Real food ingredients
Indicated for	Patients with normal or near-normal GI function	Patients with malabsorption or impaired digestion	Specific medical conditions (e.g., diabetes, renal disease)	Long-term feeding, patient preference, potentially improved GI tolerance
Caloric Density	Typically 1.0 to 2.0 kcal/ml	Varies; Often contains high MCT content for energy	Varies based on condition (e.g., renal is calorie-dense)	Varies based on ingredients; needs RDN review for homemade
Cost	Generally the least expensive option	More expensive due to processing	More expensive; cost varies by specific formula	Can vary significantly, especially for homemade
Palatability	Better for oral intake due to whole protein sources	Poor palatability due to free amino acids	Varies widely by formula and ingredients	Varies; can resemble real food flavors
Digestion	Requires normal digestive enzyme function	Requires minimal to no digestive action	Designed to match altered metabolic needs	Requires varying degrees of digestion

Conclusion

Choosing the right enteral formula is a critical component of nutritional therapy that must be tailored to the individual patient's needs and underlying medical condition. While standard polymeric formulas are suitable for most patients with normal GI function, specialized, elemental, or blenderized diets offer alternatives for those with impaired digestion, specific disease states, or a preference for real food ingredients. Close collaboration with a healthcare team, including a physician and a dietitian, is essential to select and monitor the optimal formula for safe and effective enteral nutrition. For more in-depth information, resources from organizations like the American Society for Parenteral and Enteral Nutrition (ASPEN) provide detailed practice recommendations.

Frequently Asked Questions

The main difference is the form of the nutrients. Polymeric formulas contain intact, whole nutrients that require normal digestion, whereas elemental and semi-elemental formulas contain pre-digested nutrients that are easier to absorb for those with impaired GI function.

These formulas are used for patients with specific health conditions like diabetes, kidney failure, or liver disease, where modifying the standard nutrient profile can help manage the metabolic demands of the illness.

Blenderized formulas can be safe, particularly for long-term feeding, but require careful consideration. If homemade, a dietitian's guidance is crucial to ensure nutritional adequacy and safety, as improper preparation increases the risk of contamination.

No, not all formulas contain fiber. While fiber-containing formulas are common, fiber-free options exist for patients with conditions where fiber might be contraindicated, such as certain bowel issues.

Yes, modular diets, which contain single nutrients like protein or carbohydrates, can be added to standard formulas to meet a patient's special needs. However, this should always be done under the supervision of a healthcare professional.

Formula selection is a comprehensive process involving a nutritional assessment by an RDN. Factors considered include the patient's medical history, GI function, fluid needs, metabolic state, and desired clinical outcomes.

Studies comparing elemental and polymeric formulas for inducing Crohn's disease remission have shown mixed results. While some early research suggested a benefit, meta-analyses have found no significant difference in remission rates. Polymeric formulas are often preferred due to better palatability and lower cost.