Oncologist-approved cancer information from the American Society of Clinical Oncology
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Food Safety During and After Cancer Treatment

This section has been reviewed and approved by the Cancer.Net Editorial Board, 6/2014

Key Messages:

  • If you are receiving or recovering from cancer treatment, you need to take extra precautions to protect yourself from foodborne illness, which can be severe or even deadly.
  • Certain foods are more likely to cause illness than others, such as uncooked fruits and vegetables, raw or undercooked meat and seafood, and unpasteurized dairy products.
  • There are a number of ways to prevent serious foodborne illness, including practicing food safety and knowing the symptoms you should call your doctor about right away.

Food safety is important for people both during and after cancer treatment. Cancer and cancer treatments, such as chemotherapy, radiation therapy, and stem cell/bone marrow transplantation, often weaken the immune system, making it harder for your body to protect itself from foodborne illness, also called food poisoning. Foodborne illness, which is caused by eating food that contains harmful bacteria, parasites, or viruses, can be severe and sometimes deadly.

Talk with a member of your health care team about how to safely handle, prepare, and store food, and which foods you should avoid. Also ask how long you should take food precautions and when you will be able to eat certain foods again. 

Foods to avoid

Some foods have a higher risk of becoming tainted with bacteria, such as Listeria, E. coli, Salmonella, Campylobacter, and Vibrio, in addition to Toxoplasma, a parasite. These include:

  • Unwashed fresh fruit and vegetables, especially leafy vegetables that can hide dirt and other contaminants
  • Raw sprouts, such as alfalfa sprouts
  • Raw or undercooked beef, especially ground beef, or other raw or undercooked meat and poultry
  • Cold hot dogs or deli lunch meat (cold cuts), including dry-cured, uncooked salami. Always cook or reheat these foods until they are steaming hot.
  • Refrigerated pâté
  • Raw or undercooked shellfish, such as oysters. These items may carry the hepatitis A virus and should be cooked thoroughly to destroy the virus.
  • Smoked fish
  • Some types of fish, both raw and cooked, as they may contain high levels of mercury
  • Sushi and sashimi, which often contain raw fish. Commercially frozen fish, especially those labeled “sushi-grade” or “sashimi-grade,” is safer than other fish, but check with your doctor before eating it.
  • Unpasteurized beverages, such as unpasteurized fruit juices, raw milk (including raw milk yogurt), or cider
  • Soft cheeses made from unpasteurized milk, such as blue-veined (a type of blue cheese), Brie, Camembert, feta, goat cheese, and queso fresco or blanco
  • Undercooked eggs, such as soft boiled, over easy, and poached; raw, unpasteurized eggs; or foods made with raw egg, such as homemade raw cookie dough and homemade mayonnaise
  • Deli-prepared salads with egg, ham, chicken, or seafood

Simple steps for food safety

Think about your water source. Some water sources, such as well water, may contain potentially harmful bacteria or chemicals. Community-supplied tap water is fine for healthy individuals, but it is not tested for safety for people with weakened immune systems. A water filter that removes spores and cysts, as well as trace organics and heavy metals, is recommended for food preparation and drinking. Many types of these filters are for sale in stores.

Shop smart. Do not buy food stored or displayed in an unclean area. In addition, do not buy bruised or damaged fruits or vegetables, or cans that have cracks, dents, or bulges. Pick up foods that can spoil at the end of your shopping trip and store them in a cooler on the way home.

Prepare and clean up carefully. Rinse fresh fruits and vegetables, including those labeled “organic,” under running water and dry them with a clean towel or paper towel. Also, clean the top of cans before opening them. After preparing food, wash your hands for 20 seconds with hot water and soap, paying special attention to areas between fingers and under nails. Clean your utensils and dishes with hot water and soap, and disinfect your kitchen and cutting boards using one teaspoon of liquid, unscented bleach mixed into one quart of water.  

Prevent cross-contamination. Keep raw meat, poultry, and fish or their juice away from other food since bacteria can spread, causing cross-contamination. Wash all items you used for preparing raw foods, including utensils, cutting board, and plates, before using them for other foods or cooked meat. It is ideal to set aside one specific cutting board for preparing uncooked meat and chicken and never using it for uncooked fruits, vegetables, or other foods. Do not rinse raw meat or poultry because it can spread bacteria to nearby surfaces.

Cook food to the right temperature. Use a food thermometer to check for a safe internal temperature of all poultry and meat. For instance, a hamburger should be cooked to at least medium (160˚F). Get a full list of recommended internal cooking temperatures.

Chill food promptly. Refrigerate or freeze perishable food within two hours of cooking or buying it (sooner in warm weather). Proper cooking destroys bacteria, but they can grow on cooked food if it is left out too long.

Thaw food properly. Thaw frozen food in the refrigerator rather than at room temperature. You can also thaw food in frequently changed cold water or in the microwave, but cook it as soon as it thaws.

Dispose of old food. Eat canned and packaged food before its expiration date (the “use by” or “best before” date). Consume refrigerated leftovers within three to four days. After that time, throw out the food. Even if the food does not smell or look spoiled, it still may be unsafe. Some bacteria, such as Listeria, can grow even on foods stored in the refrigerator if they are kept for too long.

Take precautions when eating out. At restaurants, avoid buffets and salad bars where food sits out for a long time and comes in contact with many people. Food can become contaminated when someone infected with a virus, often a norovirus, or another “bug” handles it. If you take home leftovers, put the food in a “to-go” container yourself, rather than having the server do it.

Symptoms of foodborne illness

Symptoms of foodborne illness differ depending on the pathogen that causes the illness. Most often, symptoms are like those of the stomach flu:

  • Diarrhea
  • Stomach pain or cramps
  • Nausea
  • Vomiting
  • Fever

Sometimes a headache and muscle pains also are present. E. coli usually does not cause a fever, and diarrhea often is bloody.

The time when symptoms begin can vary widely, from a few hours to 10 days after eating the tainted food, or even later. With Listeria, symptoms may not start until a few weeks later. But with most foodborne illnesses, people start feeling sick within the first day or two after infection.

When you suspect foodborne illness

Call your doctor right away if you think you have a foodborne illness as early treatment is important. Drink plenty of fluids to stay hydrated. Keep the suspected food or the food’s packaging materials as your doctor may want it to be examined. If you became ill due to eating food at a public place, call your local health department. By reporting it, you may help prevent other people from getting sick.

More Information

General Nutrition Recommendations

Nutrition Recommendations During and After Treatment

When to Call the Doctor During Cancer Treatment

Additional Resources

U.S. Food and Drug Administration: Food Safety for People with Cancer

U.S. Department of Health & Human Services: Food Safety

© 2005-2014 American Society of Clinical Oncology (ASCO). All rights reserved worldwide.

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