Cancer and cancer treatments may cause nutrition-related side effects. The diet is an important part of cancer treatment. Nutrition therapy can help cancer patients get the nutrients needed to maintain body weight and strength, prevent body tissue from breaking down, rebuild tissue and fight infection. Eating guidelines for cancer patients can be very different from the usual suggestions for healthful eating. Nutrition recommendations for cancer patients are designed to help the patient cope with the effects of the cancer and its treatment. Some cancer treatments are more effective if the patient is well nourished and getting enough calories and protein in the diet. People who eat well during cancer treatment may even be able to handle higher doses of certain treatments.

To ensure proper nutrition, a person has to eat and drink enough of the foods that contain key nutrients (vitamins, minerals, protein, carbohydrates, fat, and water). For many patients, however, some side effects of cancer and cancer treatments make it difficult to eat well. Appetite, taste and the ability to eat enough food or absorb the nutrients from food may be affected. Malnutrition (lack of key nutrients) can result, causing the patient to be weak, tired, and unable to resist infections or withstand cancer therapies. Eating too little protein and calories is the most common nutrition problem facing many cancer patients. Protein and calories are important for healing, fighting infection and providing energy.

Effect of Cancer on Nutrition

Anorexia, cachexia and tumors 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, when the tumor grows and spreads. Some patients may have anorexia when they are diagnosed with cancer. Almost all patients who have widespread cancer will develop anorexia. Anorexia is the most common cause of malnutrition in cancer patients.
  • Cachexia is a wasting syndrome that causes weakness and a loss of weight, fat and muscle. Anorexia and cachexia often occur together. Cachexia can occur in people who are eating enough, but who cannot absorb the nutrients. Cachexia is not related to the tumor size, type, or extent. Cancer cachexia is not the same as starvation. A healthy person's body can adjust to starvation by slowing down its use of nutrients, but in cancer patients, the body does not make this adjustment.
  • Tumors may produce 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 appear to be eating enough, but the body may not be able to absorb all the nutrients from the food. Diets higher in protein and calories can help correct this and prevent the onset of cachexia. It is important to monitor nutrition early, as cachexia is difficult to completely reverse.

Effect of Surgery on Nutrition

More than half of cancer patients have cancer-related surgery. Surgery may include the removal of all or parts of certain organs, which may affect a patient's ability to eat and digest food. Surgery increases the body's need for nutrients and energy. The body needs extra energy and nutrients to heal wounds, fight infection and recover from surgery. If the patient is malnourished before surgery, there may be complications during recovery, such as poor healing or infection. Patients with certain cancers, such as cancers of the head, neck, stomach and intestines, may be malnourished at diagnosis. Nutrition care may therefore begin before surgery.

The following are nutrition problems related to specific surgeries:

  • Surgery to the head and neck may cause chewing and swallowing problems. Mental stress due to the amount of tissue removed during surgery may affect appetite.
  • Surgery involving cancer of organs in the digestive system may lessen the ability of the digestive system to work properly and may slow the digestion of food. Removal of part of the stomach may cause a feeling of fullness before enough food has been eaten. Stomach surgery may also cause dumping syndrome (emptying of the stomach into the intestines before food is digested). Some of the organs in the digestive system normally produce important hormones and chemicals that are necessary for digestion. If surgery affects these organs, the protein, fat, vitamins, and minerals in the diet may not be absorbed normally by the body. Levels of sugar, salt, and fluid in the body may become unbalanced.

Nutrition therapy can treat these problems and help cancer patients get the nutrients they need. Nutrition therapy may include the following:

  • Nutritional supplement drinks.
  • Enteral nutrition (feeding liquid through a tube into the stomach or intestine).
  • Parenteral nutrition (feeding through a catheter into the bloodstream).
  • Medications to improve the appetite.

It is also common for patients to experience pain, tiredness, and/or loss of appetite after surgery. For a short time, some patients may not be able to eat their regular diet because of these symptoms. The following eating tips may help:

  • Avoid carbonated drinks (such as sodas) and gas-producing foods (such as beans, peas, broccoli, cabbage, brussel sprouts, green peppers, radishes, and cucumbers).
  • If regularity is a problem, increase fiber by small amounts and drink lots of water. Good sources of fiber include whole-grain cereals (such as oatmeal and bran), beans, vegetables, fruit and whole grain breads.
  • Choose high-protein and high-calorie foods to help wounds heal. Good choices include eggs, cheese, whole milk, ice cream, nuts, peanut butter, meat, poultry, and fish. Increase calories by frying foods and using gravies, mayonnaise, and salad dressings. Supplements high in calories and protein are available.

Effect of Chemotherapy on Nutrition

Chemotherapy may affect the whole body. Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. Because chemotherapy targets rapidly dividing cells, healthy cells that normally grow and divide rapidly may also be affected by the cancer treatments. These include cells in the mouth and digestive tract. Side effects that interfere with eating and digestion may occur during chemotherapy. The following side effects are common:

  • Anorexia
  • Nausea
  • Vomiting
  • Diarrhea or constipation
  • Inflammation and sores in the mouth
  • Changes in the way food tastes
  • Infections

The side effects of chemotherapy may make it difficult for a patient to obtain the nutrients needed to regain healthy blood counts between chemotherapy treatments. Nutrition therapy can treat these side effects and help chemotherapy patients get the nutrients they need to tolerate and recover from treatment, prevent weight loss, and maintain general health. Nutrition therapy may include the following:

  • Supplements high in calories and protein
  • Enteral nutrition (tube feedings)

Effect of Radiation Therapy on Nutrition

Radiation therapy can affect healthy cells in the treatment area. Radiation therapy is a cancer treatment that uses high energy X-rays or other types of radiation to kill cancer cells. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. Healthy cells that are near the cancer may be affected by the radiation treatments, and side effects may occur. The side effects depend mostly on the radiation dose and the part of the body that is treated.

Radiation therapy to any part of the digestive system is likely to cause nutrition-related side effects. The following side effects may occur:

  • Radiation therapy to the head and neck may cause anorexia, taste changes, dry mouth, inflammation of the mouth and gums, swallowing problems, jaw spasms, cavities or infection.
  • Radiation therapy to the chest may cause infection in the esophagus, swallowing problems, esophageal reflux (a backwards flow of the stomach contents into the esophagus), nausea or vomiting.
  • Radiation therapy to the abdomen or pelvis may cause diarrhea, nausea and vomiting, inflammation of the intestine or rectum, and fistula (holes) in the stomach or intestines. Long-term effects can include narrowing of the intestine, chronic inflamed intestines, poor absorption, or blockage in the stomach or intestine.
  • Radiation therapy may also cause tiredness, which can lead to a decrease in appetite and a reduced desire to eat.

Nutrition therapy during radiation treatment can provide the patient with enough protein and calories to tolerate the treatment, prevent weight loss, and maintain general health. Nutrition therapy may include the following:

  • Nutritional supplement drinks between meals
  • Enteral nutrition (tube feedings)
  • Other changes in the diet, such as eating small meals throughout the day and choosing certain kinds of foods

Goals of Nutrition Therapy

The goals of nutrition therapy for cancer patients in active treatment and recovery are designed to restore nutrient shortages, maintain nutritional health, and prevent complications.

The following are the goals of nutrition therapy for patients in active treatment and recovery:

  • Prevent or correct malnutrition
  • Prevent wasting of muscle, bone, blood, organs and other lean body mass
  • Help the patient tolerate treatment
  • Reduce nutrition-related side effects and complications
  • Maintain strength and energy
  • Protect ability to fight infection
  • Help recovery and healing
  • Maintain or improve quality of life

A patient whose religion forbids eating certain foods may consider speaking with a religious leader about waiving the restriction during cancer treatment and recovery. Good nutrition continues to be important for patients who are in remission or whose cancer has been cured.

The following are the goals of nutrition therapy for patients who have advanced cancer:

  • Reduce side effects
  • Reduce risk of infection
  • Maintain strength and energy
  • Improve quality of life

Nutrition Suggestions for Symptom Relief

When side effects of cancer or cancer treatment interfere with normal eating, adjustments can be made to ensure the patient continues to get the necessary nutrition. Medications may be given to stimulate the appetite. Eating foods that are high in calories and protein is usually advised. Meal planning, however, should be individualized to meet the patient's nutritional needs and tastes in food.


Anorexia (lack of appetite) is one of the most common problems for cancer patients. The following suggestions may help cancer patients manage anorexia:

  • Eat small high-protein and high-calorie meals every 1-2 hours instead of 3 larger meals.
  • Have help with preparing meals.
  • Add extra calories and protein to food (such as butter, skim milk powder, honey, or brown sugar).
  • Take liquid supplements (special drinks containing nutrients), soups, milk, juices, shakes, and smoothies when eating solid food is a problem.
  • Eat snacks that contain plenty of calories and protein.
  • Prepare and store small portions of favorite foods so they are ready to eat when hungry.
  • Eat breakfasts that contain one third of the calories and protein needed for the day.
  • Eat foods with odors that are appealing. Strong odors can be avoided by using boiling bags, cooking outdoors on the grill, using a kitchen fan when cooking, serving cold food instead of hot (since odors are in the rising steam), and taking off any food covers to release the odors before entering a patient's room. Small portable fans can be used to blow food odors away from patients. Cooking odors can be avoided by ordering take-out food.
  • Try new foods. Be creative with desserts. Experiment with recipes, flavorings, spices, types, and consistencies of food. Food likes and dislikes may change from day to day.
  • Try eating the more dairy products, including milkshakes, yogurt and ice cream. Or try recipes that use milk or call for adding powdered milk to foods such as pudding or milkshakes.
  • Eat finger foods (handy for snacking), such as deviled eggs; cream cheese or peanut butter on crackers or celery; or deviled ham on crackers.

Taste Changes

Changes in how foods taste may be caused by cancer treatment, dental problems or medicines. A sudden dislike for certain foods may occur. Some or all of the sense of taste may return, but it may be a year after treatment ends before the sense of taste is normal again. Drinking plenty of fluids, changing the types of foods eaten and adding spices or flavorings to food may help. The following suggestions may help cancer patients manage changes in taste:

  • Rinse mouth with water before eating.
  • Try citrus fruits (oranges, tangerines, lemons, grapefruit) unless mouth sores are present.
  • Eat small meals and healthy snacks several times a day.
  • Eat meals when hungry rather than at set mealtimes.
  • Use plastic utensils if foods taste metallic.
  • Try favorite foods.
  • Eat with family and friends.
  • Have others prepare the meal.
  • Try new foods when feeling best.
  • Substitute poultry, fish, eggs, and cheese for red meat.
  • Find nonmeat, high-protein recipes in a vegetarian or Chinese cookbook.
  • Use sugar-free lemon drops, gum, or mints if there is a metallic or bitter taste in the mouth.
  • Add spices and sauces to foods.
  • Eat meat with something sweet, such as cranberry sauce, jelly, or applesauce.

Taking zinc sulfate tablets during radiation therapy to the head and neck may speed the return of normal taste after treatment.

Dry Mouth

Dry mouth is often caused by radiation therapy to the head and neck. Some medicines may also cause dry mouth. Dry mouth may affect speech, taste, ability to swallow and the use of dentures or braces. There is also an increased risk of cavities and gum disease because less saliva is produced to wash the teeth and gums.

Suggestions to manage dry mouth include the following:

  • Drink plenty of liquids, about 1/2 ounce per pound of body weight per day
  • Eat moist foods with extra sauces, gravies, butter, or margarine.
  • Suck on hard candy or chew gum.
  • Eat frozen desserts (such as frozen grapes and ice pops) or ice chips.
  • Clean teeth (including dentures) and rinse mouth at least four times per day (after each meal and before bedtime).
  • Keep water handy at all times to moisten the mouth.
  • Avoid liquids and foods that contain a lot of sugar.
  • Avoid mouth rinses containing alcohol.
  • Drink fruit nectar instead of juice.
  • Use a straw to drink liquids.

Mouth Sores and Infections

Mouth sores can result from chemotherapy and radiation therapy. These treatments target rapidly growing cells because cancer cells grow rapidly. Normal cells inside the mouth may be damaged by these cancer treatments because they also grow rapidly. Mouth sores may become infected and bleed, making eating difficult. By choosing soft foods and taking good care of their mouths, patients can usually make eating easier.


Diarrhea may be caused by cancer treatments, surgery on the stomach or intestines, or by emotional stress. Long-term diarrhea may lead to dehydration (lack of water in the body) and/or low levels of salt and potassium, important minerals needed by the body.

Low White Blood Cell Count

Cancer patients may have a low white blood cell count for a variety of reasons, some of which include radiation therapy, chemotherapy, or the cancer itself. Patients who have a low white blood cell count are at an increased risk of infection.

Fluid Intake

The body needs plenty of water to replace the fluids lost every day. Long-term diarrhea, nausea and vomiting, and pain may prevent the patient from drinking and eating enough to get the water needed by the body. One of the first signs of dehydration (lack of water in the body) is extreme tiredness. The following suggestions may help cancer patients prevent dehydration:

  • Drink eight to 12 cups of liquids a day. This can be water, juice, milk or foods that contain a large amount of liquid such as puddings, ice cream, ice pops, flavored ices and gelatins.
  • Take a water bottle whenever leaving home. It is important to drink even if not thirsty, as thirst is not a good sign of fluid needs.
  • Limit drinks that contain caffeine, such as sodas, coffee and tea (both hot and cold).
  • Drink most liquids after and/or between meals.
  • Use medicines that help relieve nausea and vomiting


Constipation is defined as fewer than three bowel movements per week. It is a very common problem for cancer patients and may result from lack of water or fiber in the diet; lack of physical activity; anticancer therapies such as chemotherapy; and medications.Prevention of constipation is a part of cancer care. The following suggestions may help cancer patients prevent constipation:

  • Drink eight to 10 cups of fluid each day. Water, prune juice, warm juices lemonade, and teas without caffeine can be very helpful.
  • Eat more fiber-containing foods on a regular basis. The recommended fiber intake is 25 - 35 grams per day.
  • Increase fiber gradually and drink plenty of fluids at the same time to keep the fiber moving through the intestines.