Many undernourished ( Home.see chapter Undernutrition Undernutrition Undernutrition is a deficiency of calories or of one or more essential nutrients. Undernutrition may develop because people cannot obtain or prepare food, have a disorder that makes eating or... read more 
) 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 Difficulty Swallowing Some people have difficulty swallowing (dysphagia). In dysphagia, foods and/or liquids do not move normally from the throat (pharynx) to the stomach. People feel as though food or liquids become... read more ) or who have difficulty absorbing nutrients Overview of Malabsorption Malabsorption syndrome refers to a number of disorders in which nutrients from food are not absorbed properly in the small intestine. Certain disorders, infections, and surgical procedures can... read more . These people may need nutritional support.
Nutritional support includes the following:
A tube (tube feeding Tube Feeding Tube feeding may be used to feed people whose digestive tract is functioning normally but who cannot eat enough to meet their nutritional needs. Such people include those with the following... read more
), usually inserted through the nose or through the skin into the stomach or intestine
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 Nutritional Support for People Who Are Dying or Severely Demented Eventually, people who are dying lose their appetite, and people with advanced dementia become unable to eat. Family members are often concerned about providing nutrition for these people and... read more ).
Determining Nutritional Requirements
(See also Nutritional Requirements Nutritional Requirements General guidelines for a healthy diet have been developed even though daily nutritional requirements, including those for essential nutrients, vary depending on age, sex, height, weight, physical... read more .)
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 Calories A calorie is a measure of energy. Foods have calories. That is, foods supply the body with energy, which is released when foods are broken down during digestion. Energy enables cells to do all... read more . 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 Carbohydrates, Proteins, and Fats Carbohydrates, proteins, and fats are the main types of macronutrients in food (nutrients that are required daily in large quantities). They supply 90% of the dry weight of the diet and 100%... read more , protein Proteins Carbohydrates, proteins, and fats are the main types of macronutrients in food (nutrients that are required daily in large quantities). They supply 90% of the dry weight of the diet and 100%... read more , fat Fats Carbohydrates, proteins, and fats are the main types of macronutrients in food (nutrients that are required daily in large quantities). They supply 90% of the dry weight of the diet and 100%... read more , vitamins Vitamins and Minerals The human body needs various vitamins and minerals in order to thrive. Many of these nutrients can be found in whole, non-processed foods such as fruits and vegetables. However, most modern... read more , minerals Vitamins and Minerals The human body needs various vitamins and minerals in order to thrive. Many of these nutrients can be found in whole, non-processed foods such as fruits and vegetables. However, most modern... read more , fiber Fiber Some foods contain fiber, which is a tough complex carbohydrate. Fiber may be Partly soluble: It dissolves in water, and the body may be able to digest some of it. Insoluble: It does not dissolve... read more , 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.
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.
People who are over 70 years old may need extra protein.
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.
