Foods to Avoid During Cancer Treatment

Cancer treatments cause many side effects. The foods you eat can sometimes make these side effects worse or cause additional problems. Changing your diet may help improve your well-being while going through treatments for cancer.

Key takeaways:
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    Some types of foods, including items that are spicy or fatty, can worsen cancer treatment side effects like nausea, mouth sores, or dry mouth.
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    Choosing high-fiber foods in place of foods that don’t contain as much of this nutrient can help normalize your digestion and eliminate diarrhea and constipation.
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    Grapefruit, herbal products, and natural supplements can all affect how well your cancer treatments work, so talk to your doctor before using them.
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    It is important to focus on food safety measures and stay away from undercooked items if you are undergoing treatments that worsen your immune system.

The type of diet changes you need to make depends on which treatments you are receiving.

Avoiding foods that increase nausea

Most people who undergo chemotherapy deal with nausea or vomiting. Additionally, radiation treatments to certain parts of the body, such as the brain or digestive system, can lead to this side effect.

Eating foods that can be digested easily, such as crackers, bread, yogurt, and broth, may ease nausea. Choosing small portions and consuming foods that are at room temperature may also help.

You may also want to stay away from:

  • Foods that have strong smells.
  • High-fat foods.
  • Meals that are heavy, greasy, or fried.
  • Desserts and sweets.
  • Spicy foods.

Try to eat foods that sound appetizing and stay away from anything that might make you feel sicker.

Eating while living with mouth symptoms

Mouth sores may develop after you are treated with chemotherapy, immunotherapy, or radiation therapy to the head or neck area.

Soft foods are easiest to eat when you have mouth sores or related symptoms such as dry mouth or swallowing problems. Stay away from:

  • Crunchy foods with sharp edges like crackers, toast, or potato chips.
  • Oranges, lemon juice, or other citrus fruits.
  • Foods or drinks with a strong, minty flavor.
  • Hot sauce, chili peppers, and other spicy foods.
  • Tomatoes, tomato sauce, and ketchup.
  • Very hot foods or drinks.
  • Alcohol.

Rather than eating these foods, try choosing easy-to-chew foods. Cook everything until it becomes soft, and add sauce or gravy.

Managing other gastrointestinal side effects

A high-fiber diet can help treat both diarrhea and constipation. Specifically, both soluble and insoluble fiber can treat constipation, while soluble fiber can help with diarrhea.

Insoluble fiber can be found in whole-grain products, nuts, seeds, and raw fruits and vegetables. Soluble fiber is present in oats, lentils, flaxseeds, chia seeds, and applesauce.

Choose foods with fiber whenever possible. Stay away from things like white bread, white pasta, canned or cooked vegetables, and dairy products, which don’t offer as much fiber.


While grapefruit and grapefruit juice can be healthy, these items can interact with many drugs. In some cases, grapefruit can make drugs less effective. For other medications, grapefruit can make the drugs stay in the body too long, increasing side effects.

Ask your doctor if grapefruit is safe to use with your treatment plan. Alternatively, avoid grapefruit and grapefruit juice while going through cancer treatments.


Most people assume that supplements are generally safe to use, especially if they’re herbal or natural. However, many supplements — including herbal products — can make cancer treatments less effective.

Cancer experts don’t agree on whether or not antioxidants help or hurt during cancer treatment. Some studies show that antioxidants may lessen side effects and help chemotherapy work better. However, other research has found that people who use antioxidant supplements besides a multivitamin may be more likely to have their cancer come back after being treated. Ask your doctor whether taking antioxidants, including vitamins A, C, and E and coenzyme Q10, are safe to use with your cancer treatment.

Green tea is usually extremely safe and healthy. However, it may interfere with bortezomib (Velcade), a medication sometimes used to treat blood cancers.

Always tell your cancer care team about any supplements you are taking, and ask before starting a new supplement.

Food safety

Food safety may become much more important when you are living with cancer. Many types of cancer treatments, and occasionally cancer itself, can make it harder for your immune system to fight infection. People undergoing radiation, chemotherapy, or other medications may have lower levels of white blood cells and have an increased chance of developing an illness from improperly handled food.

To stay safe while living with a compromised immune system, avoid eating:

  • Unwashed vegetables and fruits.
  • Raw vegetable sprouts.
  • Deli meats or undercooked hot dogs.
  • Brie, stilton, blue cheese, and other soft cheeses.
  • Unpasteurized milk.
  • Raw fish, oysters, sushi, or sashimi.
  • Undercooked meats or eggs.
  • Hot or cold foods that have been left at room temperature for a long time.
  • Any foods or drinks that are past their expiration date or seem like they might be going bad.

You can also lessen your risk of infection by avoiding buffets, potlucks, and shared foods, by storing foods at the proper temperature, and by using defrosted items right away.

Knowing which foods to cut out of your diet

It may take some trial and error before you find a diet that minimizes symptoms and helps you stay comfortable while you are going through cancer treatments. Try to find what works for you — the same strategies may not work for every person.

Always talk to your cancer care team before making any major changes to your diet. Your doctor can help you understand whether eating or avoiding certain foods is safe for you based on your treatment plan and overall health.


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