Causes of Undernutrition

As people age, the body changes in several ways that may cause older people to eat less. The aging body produces more hormones that decrease appetite and fewer chemical messengers (neurotransmitters) that stimulate appetite. Thus, older people tend to feel satisfied with less food. The ability to taste or smell gradually diminishes, so food becomes less appetizing. Some older people produce less saliva, making the mouth feel dry. As a result, chewing and swallowing food may be difficult. When older people become less physically active, they may eat less. Physical activity stimulates the appetite.

Disorders can increase the risk of undernutrition by changing the body's nutritional needs or by changing the body's ability to meet those needs. For example, an overactive thyroid gland (hyperthyroidism) increases the amount of nutrients needed because it changes the way the body uses nutrients.

Some disorders cause symptoms that interfere with the body's ability to meet nutritional needs. For example, nausea makes a person eat less. Vomiting or diarrhea prevents the body from absorbing as many nutrients. Liver or kidney failure can cause these symptoms. Some disorders, sometimes called malabsorption disorders, interfere with the absorption of nutrients in the digestive tract. Examples are liver failure, lactose intolerance, and disorders of the pancreas. A stroke can make swallowing difficult.

Dental problems, such as tooth decay, gum disease, missing or loose teeth, and poorly fitting bridges or dentures, can make eating and drinking awkward or painful. Thus, eating may become more of a necessity than a pleasure, even for relatively healthy older people.

Some disorders, such as Parkinson's disease, can make shopping for, preparing, and eating food more difficult. Being frail, apart from any disorder, can also make these tasks difficult.

Depression or anxiety disorders can decrease appetite. Depression is more likely to lead to undernutrition in older people than in younger people.

Some disorders change the body's nutritional needs and the ability to meet those needs. For example, some disorders increase the body's requirements for energy and decrease appetite. That is, even though the disorder causes the body to use more calories, people with one of these disorders tend to eat less. Examples are cancer, infections, chronic obstructive pulmonary disease (COPD), and rheumatoid arthritis. Such disorders typically cause weight to be lost slowly over time. COPD also may make people breathless while eating, so that they eat less.

Diabetes changes the body's nutritional needs by changing the way the body handles sugar. Consequently, people with diabetes should substitute complex carbohydrates (found, for example, in beans, many other vegetables, and whole-grain foods) for simple sugars (found, for example, in ice cream, candy, syrups, jellies, and sodas). Also, diabetes can interfere with the body's ability to meet nutritional needs by changing how quickly food moves through the digestive tract. Nausea and abdominal pain may result, causing a person to eat less.

Drugs can increase the risk of undernutrition by changing the body's nutritional needs. Some drugs (such as thyroxine and theophylline) increase the body's requirements for energy. Other drugs can change the way the body uses nutrients.

Drugs can also change the body's ability to meet nutritional needs. Many drugs can decrease appetite. Examples are some drugs used to treat depression (such as fluoxetine and sertraline), high blood pressure (such as diuretics), heart failure (such as digoxin), and chemotherapy drugs (such as cisplatin). If older people notice a decrease in their appetite after they start taking a new drug, they should tell their doctor.

Some drugs can have side effects that interfere with meeting nutritional needs. These side effects include nausea, upset stomach, diarrhea, and constipation (which can greatly decrease appetite). Other drugs alter taste or smell. As a result, many foods may no longer taste good, so less food is eaten. Some drugs (such as cholestyramine) interfere with the absorption of nutrients, as does taking too many laxatives. Certain drugs (such as some antidepressants and antipsychotics) increase appetite. When people stop taking these drugs, they may eat less and thus lose weight.

Drinking too much alcohol can lead to undernutrition. Alcohol has little nutritional value. It also decreases appetite. Alcohol can interfere with the absorption and use of nutrients partly because it damages the liver.

Smoking dulls taste and smell, so smokers may eat less. Smoking increases the metabolic rate, causing the body to burn more calories. Smoking also causes many types of cancer, which can lead to weight loss and sometimes undernutrition.

Many older people live alone. For them, preparing meals just for themselves may seem like too much trouble. Or they may not enjoy eating alone. They may make the same meals for themselves day after day. As a result, they may not consume enough of some nutrients. Or they may snack throughout the day without eating a well-balanced meal. Older people who live alone may not have transportation to a grocery store. Or they may be afraid of going out alone or be physically unable to do so. They may need help preparing meals. Loneliness, especially after losing a partner, may make people feel less like eating.

Older people who have a caregiver may develop undernutrition. Caregivers may not know what the nutritional needs of older people are. They may not realize how little the person is eating. Or they may not think about nutrition at all.

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