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Commercial Formulas for the Feeding Tube

There are over 100 commonly used brand names of commercially prepared formula available, so there is no shortage of options to choose from when you and your doctor, or nutritionist, decide which formula is right for you. An easy way to distinguish all the different types of commercial liquid nutrition is by their fat, carbohydrate, and protein (or macronutrient) sources. Using this method, there are three different categories of formulas: standard, elemental, and specialized.

Standard formulas are the most commonly used by G-tube patients. They contain proteins that haven't been broken down (intact proteins) and polysaccharides. The proteins are normally extracted from cow's milk, soybeans, or protein isolates derived from other food sources. The carbohydrate component is typically glucose polymers, such as maltodextrin, modified starches, and all varieties of sugar. The fats for standard formulas are typically heat- or chemically-extracted from plant sources. They could also include fish oils or modified oils such as MCT oils taken from coconut and palm oils.

Standard formulas are intended for patients who are able to absorb and digest nutrients without difficulty. Their goal is to provide the entire spectrum of macro- and micro-nutrients necessary for human nutrition. The differences among standard formula brands and products come from proportions and sources of ingredients.

Here are some examples of typical macronutrient ingredients in standard formulas:

Carbohydrates:

  • Corn syrup solids
  • Maltodextrin
  • Hydrolysed cornstarch
  • Glucose
  • Fructose
  • Sucrose
  • Sugar alcohols

Proteins:

  • Casein
  • Whey protein concentrate
  • Milk protein concentrate
  • Soy protein isolate
  • Lactalbumin
  • Sodium, calcium, potassium, and magnesium caseinates

Fats:

  • Soybean oil
  • Corn oil
  • Canola oil
  • Palm kernel oil
  • Medium chain triglycerides (MCT) oil
  • Safflower oil
  • High-oleic sunflower oil
  • Borage oil
  • Fish oil
  • Monoglycerides
  • Diglycerides
  • Soy lecithin

Each brand of formula also includes micronutrients, vitamins, and minerals deemed to be essential for nutrition.

There are several standard formulas available in pharmacies, grocery stores, or online in the form or flavored oral supplements like Ensure, Boost, or Carnation Instant Breakfast. Also, some stores have generic, store brands of standard formulas at a cheaper price (Walmart has Equate, Target has Market Pantry Nutrition Shakes, etc.). They can be ready-to-go out of the can or in the form of powder, requiring reconstitution with milk or water. Taking 6-7 Ensure Pluses a day can get pricey--especially long-term--but you may be able to get your insurance company to reimburse you if you have a doctor's prescription. Talk to your doctor about this.

Elemental formulas (also known as monomeric, hydrolysed, or chemically defined formulas) are different from standard formulas because their macronutrients have already been partly or fully broken down for those patients who have compromised digestive systems or nutrient absorption problems. These formulas are not commonly needed by oral cancer patients. J tube patients usually eat elemental formulas, and some G tube patients may be prescribed elemental formulas in certain instances.

While a standard formula typically has whole proteins, like casein, elemental formulas have broken down--or hydrolysed--versions of the casein in the form of amino acids. This allows the body to digest and absorb what it needs from the formula more easily. Just like in standard formulas, the goal of elemental formulas is to give a complete spectrum of macro- and micro-nutrients, however these formulas tend to be lower in fat because fat is harder for people to digest. MCT oil is commonly the fat of choice because it is absorbed, rather than digested.

Elemental formulas are not usually in stores, however they can be found online (abbottnutrition.com, amazon.com, and nestlehealthscience.com are good websites to check). Optimental, Pivot, Tolerex and Vivonex are all examples of elemental formulas. You can purchase them online, and you may be able to get insurance to cover the cost with a doctor's prescription. You need to speak to your doctor or nutritionist before taking an elemental formula to ensure you're getting the best nutrition. Here are common ingredients in elemental formulas:

Carbohydrates:

  • Cornstarch
  • Hydrolysed cornstarch
  • Fructose
  • Maltodextrin

Proteins:

  • Soy protein isolate
  • Crystalline L-amino acids
  • Hydrolysed casein
  • Hydrolysed whey protein
  • Hydrolysed lactalbumin

Fats:

  • Fatty acid esters
  • MCT oil
  • Soybean oil
  • Safflower oil
  • Fish oil
  • Sardine oil
  • Structured lipids
  • Soy lecithin

Specialized formulas are prescribed to address specific disease categories or profiles. It is quite possible for a doctor or nutritionist to prescribe a specialized formula to an oral cancer patient if the patient has diabetes or certain allergies. Standard formulas typically contain a lot of sugar. This is so that they can fit a high number of calories in a relatively small volume while staying liquid. This could become an issue for patients with diabetes mellitus or other problems with hyperglycemia. Although formula companies strive to keep their products 'well-rounded', in practice many formulas cause a sugar rush ('glycemic spike') and consequent comedown. So, specialized diabetic formulas have a higher percentage of fats with lower amounts of carbohydrates. The carbohydrates in diabetic formulas have a lower glycemic index so that the sugars are converted more slowly before they're released into the bloodstream. These formulas also contain more fiber, to slow the breakdown of carbohydrates even more. Two prime examples of specialized formulas for diabetic patients are Glucerna and Boost Glucose Control. As stated earlier, these products are available over-the-counter (at pharmacies like Walgreens or you could order online), and you may be able to get your insurance to pay for it, or reimburse you, with a doctor's prescription.

Another reason specialized formulas could be prescribed to oral cancer patients is because of allergies. Unfortunately, some of the most common food allergens (such as soy, milk, wheat, and corn) are major ingredients in a a large percentage of commercial formula. To meet the need for allergen-free products, there are lactose-free formulas for those with lactose intolerance (Ensure, TwoCal, and Boost, among others, say they are suitable for lactose intolerance), gluten-free formulas for patients with celiac disease (TwoCal and Vivonex are two of several), soy-free formulas (Perative, Pivot, TwoCal, Tolorex, Vivonex), and at least one corn-free formula (Vivonex TEN actually contains corn but is processed in such away that it is hypoallergenic). One important note for those with severe allergies is that production lines for these formulas are often also used to handle products that contain their allergen, so cross-contamination is possible.

Some factors to consider when choosing a formula with your doctor or nutritionist:

Formulas commonly come in different strengths or caloric densities, classified with numbers from 0.5 to 2. This refers to the number of calories per milliliter. A 'regular' strength formula is a 1, which is about 30 Cal/oz. You could be prescribed a Low-Cal formula (0.5), a 1.2, a Hi-Cal formula (1.5) or a Two-Cal (2.0). For the most part, the lower the caloric density, the easier the formula will be to tolerate. Higher caloric densities could be prescribed when patients are unable to take in enough volume to meet their nutritional needs, or if they have fluid restrictions or above average energy needs.

It's important to remember that formulas with high-caloric density have a lower water content. Therefore, unless the patient is fluid-restricted, he/she will be required to drink more free water with higher strength formulas. Lower strength formulas, like Ensure or Boost, are around 85% water, while 2 Cal/ml formulas (TwoCal or Boost VHC) are about 70%. It's important to factor this in when determining the patient's total daily water intake.

Free water is water by itself, without being mixed in with foods, supplements, electrolytes, or medicines. It is vital for all tube-fed patients to have free water because the body reacts differently to water on its own than it does to anything else. When we eat or drink anything with calories, our bodies can discern that the food needs digestion and act accordingly. We secrete acid, tailor enzymes according to the nutrients, and activate paristalsis (muscle contractions in the digestive tract). Our systems can even assess the fat content of the food we've eaten and slow down gastric emptying as a result. This happens every time we consume something needing digestion. However, it doesn't happen with pure water. When we drink water on its own, the water is absorbed quickly through the gut walls to be used for vital bodily functions.

There are so many reasons why free water is necessary for tube-fed patients. One obvious reason is that water cleans feeding tubes before and after meals. It also aids stomach emptying between meals. Drinking free water 30 minutes to an hour before meals can help volume tolerance because it 'primes' the stomach to begin digesting. Water assists with general digestion health, fixing many constipation, diarrhea, and reflux issues. Finally, water helps to flush out our kidneys.

Another factor to consider when choosing a formula is that regular-strength formulas, high-caloric-density formulas and elemental formulas are absorbed by your gut at different rates. Elemental and high calorie formulas are described as hypertonic, and are not absorbed as readily as regular formulas (isotonic formulas). This could cause diarrhea, or some other type of digestive issue, and it's another reason to put more free water through the tube.

Formulas are more than likely to contain some type of fiber, whether it's soluble or insoluble. The soluble fiber-of-choice for most formulas is FOS (fructo-oligo-saccharides). FOS acts as fuel for good bacteria in our stomachs, helping them perform necessary dietary functions. Soluble fiber also strengthens the lining of our GI tract and aids water and sodium absorption. Insoluble fibers give bulk to fecal matter and help it pass through the intestines more quickly. Insoluble fiber is another vital part of our diets. It helps manage diarrhea and constipation, and supports the regulation of blood glucose levels. However, certain patients with intestinal or digestive problems should be aware of fiber levels in their formula as fiber may exacerbate their issues.

A fifth factor we'll highlight is formula intolerance. Commercial formulas can be difficult to tolerate, especially over the long-term. This intolerance presents itself like any other type of food intolerance or allergy. The patient could see various symptoms like reflux, constipation, diarrhea, nausea, retching, vomiting, or any other allergic reaction. This could be from a specific ingredient in the formula, or it could simply be a matter or drinking the same product multiple times a day for months or even years. Formula manufacturers claim that their products provide patients with all their dietary needs. This is a dubious claim. New compounds in our food are discovered with amazing health-giving properties on a weekly basis. Commercial companies could never replicate the nutrients contained in a varied diet. Also, as stated earlier, formulas contain a lot of sugar--usually in the form of corn syrup--which is not ideal long-term nutrition.

Therefore, while commercial formulas are perfectly fine to consume as a sole source of nutrition over a short period of time (6-8 months), the OCF recommends that oral cancer patients with long-term feeding tubes look into alternate ideas, such as blending meals, for a complete and healthy diet. Of course, some patients have no choice in this matter and cannot deviate from a commercial formula diet. As we've stated multiple times, patients need to consult their doctor or nutritionist before making dietary changes.