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Overview of Nutritional Support


David R. Thomas

, MD, St. Louis University School of Medicine

Last full review/revision Jul 2020| Content last modified Jul 2020
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Topic Resources

Many undernourished (see Undernutrition) and critically ill people need additional nutrition (nutritional support). Artificial feeding, which uses commercial nutrient mixtures rather than food, is a common form of nutritional support. Nutritional support is intended to increase the amount of muscle tissue (muscle mass). It usually provides calories as well as vitamins and minerals.

Nutrients are given by mouth whenever possible, ideally as regular food. When people are reluctant to eat, the following strategies can sometimes help them eat more regular food:

  • Actively encouraging them to eat

  • Encouraging them to eat small amounts and to eat often

  • Heating or seasoning foods

  • Providing favorite or strongly flavored foods

  • Making meal times a priority when planning the day's activities

  • Helping them eat if needed

However, these strategies are not enough for some people. For example, these strategies do not help people who cannot eat because of injuries or other physical problems (such as difficulty swallowing) or who have difficulty absorbing nutrients. These people may need nutritional support.

Nutritional support includes the following:

  • A tube (tube feeding), usually inserted through the nose or through the skin into the stomach or intestine

  • A catheter inserted in a vein (intravenous feeding)

With tube feedings, nutrients go directly into the stomach or small intestine.

If people are dying or have advanced dementia, artificial feeding is usually not recommended (see Nutritional Support for People Who Are Dying or Severely Demented).

Determining Nutritional Requirements

Before starting nutritional support, doctors must first determine the amount and mix of nutrients the person needs. People need a certain amount of nutrients for energy, which is measured in calories. The number of calories people need varies depending on the following:

  • Their weight

  • Their activity level

  • The demands created by illness

The mix of nutrients typically includes carbohydrates, protein, fat, vitamins, minerals, fiber, and fluids.

Usually, doctors estimate the person's needs using equations based on the person's weight, height, age, sex, and activity level. Doctors adjust the requirements if the person has a condition that increases the need for calories, such as a serious illness, kidney failure that requires dialysis, an infection, an injury, or recent surgery, or if the person is over 70 years old. Some centers use a special technique to obtain a more accurate estimate. This technique measures how much oxygen is inhaled and how much carbon dioxide is exhaled—an indication of how much energy the body is using.

Did You Know...

  • Certain conditions, such as serious illnesses, kidney failure, infections, injuries, and surgery, and older age can increase the need for nutrients.

Monitoring Nutritional Support

Health care practitioners must carefully manage artificial feeding methods to make sure people are receiving the nutrients they need and to prevent problems, such as infections. To determine whether nutritional support is appropriate and effective, doctors regularly monitor factors such as the following:

  • Body mass index (BMI—weight in kilograms divided by height in meters squared)

  • Body composition (the amount of fat and muscle tissue)

  • Substances in blood, urine, and stool that indicate nutritional status

  • Muscle strength (for example, by measuring how strong the hand grip is)

An increase in muscle strength indicates an increase in muscle mass and thus improved nutritional status.

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