Good nutrition is important for cancer patients.

Nutrition is a process in which food is taken in and used by the body for growth, to keep the body healthy, and to replace tissue. Good nutrition is important for good health. Eating the right kinds of foods before, during, and after cancer treatment can help the patient feel better and stay stronger. A healthy diet includes eating and drinking enough of the foods and liquids that have the important nutrients (vitamins, minerals, protein, carbohydrates, fat, and water) the body needs.

When the body does not get or cannot absorb the nutrients needed for health, it causes a condition called malnutrition or malnourishment.

This summary is about nutrition in adults with cancer.

Healthy eating habits are important during cancer treatment.

Nutrition therapy is used to help cancer patients get the nutrients they need to keep up their body weight and strength, keep body tissue healthy, and fight infection. Eating habits that are good for cancer patients can be very different from the usual healthy eating guidelines.

Healthy eating habits and good nutrition can help patients deal with the effects of cancer and its treatment. Some cancer treatments work better when the patient is well nourished and gets enough calories and protein in the diet. Patients who are well nourished may have a better prognosis (chance of recovery) and quality of life.

Cancer can change the way the body uses food.

Some tumors make chemicals that change the way the body uses certain nutrients. The body's use of protein, carbohydrates, and fat may be affected, especially by tumors of the stomach or intestines. A patient may seem to be eating enough, but the body may not be able to absorb all the nutrients from the food.

Cancer and cancer treatments may affect nutrition.

For many patients, the effects of cancer and cancer treatments make it hard to eat well. Cancer treatments that affect nutrition include:

• Surgery.
• Chemotherapy.
• Radiation therapy.
• Immunotherapy.
• Stem cell transplant.

When the head, neck, esophagus, stomach, or intestines are affected by the cancer treatment, it is very hard to take in enough nutrients to stay healthy.

The side effects of cancer and cancer treatment that can affect eating include:

• Anorexia (loss of appetite).
• Mouth sores.
• Dry mouth.
• Trouble swallowing.
• Nausea.
• Vomiting.
• Diarrhea.
• Constipation.
• Pain.
• Depression.
• Anxiety.

Cancer and cancer treatments may affect taste, smell, appetite, and the ability to eat enough food or absorb the nutrients from food. This can cause malnutrition (a condition caused by a lack of key nutrients). Malnutrition can cause the patient to be weak, tired, and unable to fight infections or get through cancer treatment. Malnutrition may be made worse if the cancer grows or spreads. Eating too little protein and calories is a very common problem for cancer patients. Having enough protein and calories is important for healing, fighting infection, and having enough energy.

Anorexia and cachexia are common causes of malnutrition in cancer patients.

Anorexia (the loss of appetite or desire to eat) is a common symptom in people with cancer. Anorexia may occur early in the disease or later, if the cancer grows or spreads. Some patients already have anorexia when they are diagnosed with cancer. Almost all patients who have advanced cancer will have anorexia. Anorexia is the most common cause of malnutrition in cancer patients.

Cachexia is a condition marked by a loss of appetite, weight loss, muscle loss, and general weakness. It is common in patients with tumors of the lung, pancreas, and upper gastrointestinal tract. It is important to watch for and treat cachexia early in cancer treatment because it is hard to correct.

Cancer patients may have anorexia and cachexia at the same time. Weight loss can be caused by eating fewer calories, using more calories, or both.

It is important to treat weight loss caused by cancer and its treatment.

It is important that cancer symptoms and side effects that affect eating and cause weight loss are treated early. Both nutrition therapy and medicine can help the patient stay at a healthy weight. Medicine may be used for the following:

• To help increase appetite.
• To help digest food.
• To help the muscles of the stomach and intestines contract (to keep food moving along).
• To prevent or treat nausea and vomiting.
• To prevent or treat diarrhea.
• To prevent or treat constipation.
• To prevent and treat mouth problems (such as dry mouth, infection, pain, and sores).
• To prevent and treat pain.

See the Nutrition Therapy in Cancer Care section and the Treatment of Symptoms section for more information.