What is Enteral Nutrition?

Have you ever heard of enteral nutrition? We're going to tell you everything you need to know about this particular feeding method.

Written and verified by el nutricionista Saúl Sánchez.

Last update: 27 June, 2023

Enteral nutrition is a feeding method that’s used on certain special occasions to solve dietary problems. Its use is frequent in patients who are in the hospital or who have difficulties with swallowing. Also, in the case of athletes, it can be put into practice.

However, substituting a normal diet for an enteral nutrition regimen isn’t recommended as long as there’s no justified reason involved. If the body is only given this type of diet, the synthesis of some important digestive enzymes could be blocked, causing damage in the medium term.

What is enteral nutrition?

Under the name of enteral nutrition, a dietary mechanism is known by which food is administered in a liquid state, either orally or through a tube. This method facilitates digestion and the absorption of nutrients, as it’s there’s no need to chew the food or decompose it in the digestive tract.

For example, enteral nutrition is often given to patients admitted to the hospital who have difficulty consuming normal food. In cases of dysphagia (difficulty swallowing), this mechanism is very useful to avoid episodes of malnutrition. Likewise, it can be started when you need to generate an increase in weight.

In those patients who lose muscle tissue due to protein catabolism problems, it’s also beneficial to propose an enteral nutrition protocol. Typically, it’s easier for people with a poor appetite to ingest calories from liquids than from solids. It’s common for those who experience loss of lean mass tend to have an altered satiety mechanism.

In the case of athletes, enteral nutrition can be used as a reinforcement mechanism to the usual diet. The objective is to ensure that nutritional requirements are met. In these cases, specific formulas are designed with a high concentration of proteins of high biological value or essential micronutrients that are at risk of deficiency.

However, it should be noted that some recent medical documents discard this last concept within enteral nutrition. They understand enteral nutrition to be only the feeding administered by tube directly to the gastrointestinal tract.

Types of formulas in enteral nutrition

Within the products administered in enteral nutrition, several types of formulas can be differentiated according to their characteristics and functions. These are as follows:

• Polymeric. In this case, the macronutrients are whole, without any prior hydrolysis mechanism. They’re products indicated for those who experience swallowing problems, but not intestinal difficulties in terms of digestion or metabolism.
• Peptides. These formulas do have hydrolyzed proteins. In addition, a good part of the administered lipids is in the form of medium-chain triglycerides to facilitate their absorption. At the same time, they are usually lactose-free products inside, as they use dextrinomaltose as the main source of carbohydrates. Thanks to these changes, easy digestion is achieved.
• Elementary. In this case, proteins aren’t administered as such, but rather amino acids. It’s important that all the essentials are incorporated into the product to avoid deficits that can condition the health of the lean mass. Lipids are administered in the form of medium-chain triglycerides and hydrolyzed dextrins are the main source of sugars. These formulas are used in the case of the most critical patients with severe functional alterations of the digestive tract.

Classification according to energy

It’s also possible to classify these enteral nutrition formulas depending on their energy-protein density. Not all patients have the same nutritional requirements, so it’s important to adapt the diet to each individual case to facilitate recovery or to achieve the best results. We can differentiate between the following types:

• Standard. These products provide 1 calorie per milliliter consumed. They’re usually the most used, especially in the case of patients who are stable or who are progressing favorably. Exceptionally, some nutrient is added to the elderly to facilitate recovery or to cover possible deficiencies, such as glutamine. It has been shown to be effective in improving digestive health in hospitalized patients.
• Hypercaloric. These provide between 1.5 and 2 calories per milliliter of product. They usually have a higher proportion of fat and are administered to those patients who are undernourished or who lose weight in an involuntary and alarming way.
• Hypercaloric and hyperprotein. In addition to the energy value reflected in the previous case, a protein concentration greater than 18% of the total energy is ensured. It’s an effective mechanism to prevent muscle catabolism in people with cachexia due to antineoplastic treatment, for example. It must be taken into account that meeting protein requirements is considered essential.

Infant formulas

Enteral nutrition can also be applied to infants. Its administration is common in premature babies or in children with very low birth weight. However, the formulas chosen are specific to the situation and different from those already mentioned. Among them, the following stand out:

• Breastmilk. It’s the best option for newborns. According to research published in the journal La Pediatria Medica e Chirurgica, this is the best food for the first months of life. Despite this, some cases require the fortification of the food with certain higher nutrients, such as omega-3 fatty acids.
• Start-up and follow-up formulas. These are products specifically designed to meet the nutritional requirements of babies under one year of age. They have high-quality nutrients and cover the needs to avoid deficits.
• Concentrated formulas. In some cases, it’s necessary to administer more energy or protein. In such situations, concentrated formulas are used, as they provide nutrients in higher amounts and allow the child’s weight gain and proper development to be promoted.
• Special formulas for infants. Some products have been designed for specific situations in newborns, such as kidney failure or liver problems.
• Peptide Infant Formulas. In the case of those babies who have difficulties when digesting and metabolizing proteins, products that have these hydrolyzed nutrients inside can be administered.

The tubes used

We’ve discussed that enteral nutrition is often administered through a tube. This ensures that it correctly reaches the stomach pouch or specific parts of the digestive tract. The most common is to use silicone or polyurethane tubes, as they have the longest useful life and the fewest hygienic problems.

They have another advantage, and that is that they’re soft and easy to install. They don’t harden over time, which could cause discomfort in the patient, which would make this feeding method difficult. Normally, they’re placed with guides that facilitate the accommodation of the material and that are extracted once the insertion has been completed.

It’s possible to vary the caliber of the tubes used. This parameter is measured in special units, known as French sizes (Fr). In the case of infants, smaller diameters are always used, that is, 5-6 Fr. However, this type of tube only allows the passage of very liquid formulas. They’re not useful for adults, as the nutritional requirements are higher.

In these situations, it’s important to opt for a caliber greater than 8 Fr, as through these tubes, more viscous solutions can be administered, with a higher concentration of calories and nutrients. However, caution should be exercised when the type of formula administration is by continuous infusion. Choosing a product that’s too viscous could end up clogging the tube.

It should be noted that the tubes can also be differentiated according to the location of their distal end. In this case, they’re classified as nasogastric, nasoduodenal, and nasojejunal. Nasogastric surgery is normally applied, as long as the intestinal functional capacity is intact.

Infusion sets

There are two basic methods to ensure continuous delivery of formula to the patient through the tube. In the first place, the mechanism of gravity stands out, which isn’t recommended in the case of pediatric patients. Also, it’s possible to use an infusion pump that ensures a constant flow of the formula.

At the other end of the scale is the bolus infusion method, in which a certain amount of formula is manually administered. Normally, a certain volume is prescribed every few hours to ensure a correct and relatively continuous supply of nutrients.

Diet management techniques

There are several techniques to manage the total daily diet according to the possibilities and the condition of each patient. These are as follows:

• Single bolus or multiple boluses. In this case, the formula is administered every few minutes in a volume of between 200 and 400 milliliters. You have to be careful not to overdo the amounts, as you could experience bloating, vomiting, and diarrhea.
• Rapid, intermittent drip. This is the name given to the drop-by-drop administration of the formula for a maximum period of 30 minutes.
• Drop-by-drop at low continuous flow. This is considered the method of choice, especially in the case of patients with digestive problems. It’s a well-tolerated technique for diets with high osmolarity. It normally causes a reduction in gastric distention and the risk of aspiration. A lower thermogenic effect is also experienced.

Complications of enteral nutrition

Despite being a recurrent method in the hospital setting, enteral nutrition isn’t without complications. This is evidenced by a study published in Nutrients. It’s an invasive mechanism that causes discomfort to the patient. However, it’s always a preferred choice over intravenous lines.

The most important complication of enteral nutrition is pulmonary aspiration. It occurs when gastric emptying doesn’t follow a logical process. Some factors such as the type of diet administered and its osmolarity can influence the development of this problem. Still, upper body elevation reduces risks.

Regarding infectious complications, they’re more frequent when the tube used is nasogastric. Contamination with a pathogenic microorganism may be experienced, either during tube handling or during formulation preparation.

There’s the option of experiencing metabolic complications. They’re not usually frequent if the formula is chosen well. However, in cases in which the tolerance to the product isn’t previously verified, side effects can be generated.

The importance of proteins in enteral nutrition

In the context of enteral nutrition, it’s really crucial to ensure a correct protein intake. Under normal conditions, the requirements of these nutrients are estimated in amounts greater than 0.8 grams per kilogram of weight per day. This is stated by a study published in the Annals of Nutrition & Metabolism journal. However, in patients who require this type of feeding, they may be increased.

Many diseases occur with the destruction of muscle tissue from protein catabolism. Therefore, it’s best to increase the daily intake of proteins, prioritizing those of high biological value. Some amino acids such as leucine are of special importance.

There are patients in whom it’s beneficial to limit the sugar content of the enteral formula to maximize the concentration of proteins and fats. With this mechanism, a state of ketosis could be achieved. This can be adequate to prevent negative changes in body composition, and there’s even evidence of its benefits during the treatment of certain types of cancer.

It’s advisable to provide quality fatty acids in optimal proportions. It’s beneficial to ensure that the ratio of omega-3 to omega-6 is close to 1 in these types of formulas. According to a study published in the journal Prostaglandins, Leukotrienes and Essential Fatty Acids, with this nutritional mechanism, an effective modulation of inflammation is achieved.

Finally, it’s essential to meet the requirements of essential micronutrients. These compounds help to improve the efficiency of physiological processes, shortening the recovery time and hospital stay. Iron, zinc, selenium, calcium, and potassium are determinants, and their optimal concentrations depend on the patient’s disease.

When can enteral nutrition not be applied?

Despite its benefits in certain hospitalized patients, enteral nutrition has certain limitations regarding its application. This feeding method is totally contraindicated when there’s intestinal obstruction, gastroduodenal perforation, acute digestive bleeding, or abdominal injuries that require emergency surgery.

In these cases, nutrition must be carried out parenterally, that is, through an intravenous route. This mechanism is more aggressive and has a higher spectrum of side effects and complications. Whenever possible, the enteral route should be preferred.

Enteral nutrition: A mechanism used especially in the hospital context

Enteral nutrition is mainly used to achieve a good state of nutrition in those patients who have problems with swallowing or who can’t ingest solids for different reasons. Even so, some authors also include the administration of formulas or oral supplements within this type of nutrition.

It’s a feeding mechanism that facilitates the recovery of patients in serious condition through an optimal nutritional contribution. There are different mechanisms for the administration of the formulas and several classes of products that cater to the individual needs of the patients.

Of course, it’s not a method without complications or risks, so the preferred option will always be oral feeding, if possible. Whenever you need to get a tube and give yourself a nutritional formula, you have to have specialists make the right choices.