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What to Eat to Support Your Health During Cancer Treatment

Navigating Treatment

December 14, 2023

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Photography by CWP, LLC/Stocksy United

Photography by CWP, LLC/Stocksy United

by Jillian Kubala, MS, RD


Medically Reviewed by:

Teresa Hagan Thomas PHD, BA, RN


by Jillian Kubala, MS, RD


Medically Reviewed by:

Teresa Hagan Thomas PHD, BA, RN


Treatment may affect your appetite, but you can meet your nutritional needs while navigating side effects. You can try eating soft, bland, high protein foods and avoiding high fat, highly processed, and acidic foods.

When you’re living with breast cancer, nourishing your body with nutritious foods can give you energy, support your immune system, and help you maintain your weight.

But certain treatments, such as chemotherapy and radiation, can make healthy eating a bit more complicated.

These treatments can change your appetite and lead to side effects, including nausea, mouth sores, taste changes, diarrhea, and constipation. That’s why choosing the right foods during cancer treatment can be a big help.

Below, I’ll explain how your diet may change during cancer treatment and provide some tips to help you stay healthy and nourished.

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Why might your diet change during cancer treatment?

Depending on the type and severity of your cancer, your healthcare team may recommend different treatment options, such as:

  • surgery
  • radiation therapy
  • hormone therapy
  • chemotherapy

Though these treatments are often necessary, they can come with negative side effects that can significantly affect your quality of life.

Chemotherapy involves treatment with chemicals that you receive as intravenous infusions (directly into a vein) or take by mouth. These drugs affect both cancerous and healthy cells.

They can cause side effects such as:

  • inflammation in your mouth and gastrointestinal tract
  • nausea
  • diarrhea
  • fatigue
  • damage to your taste buds
  • immune system suppression

Radiation is commonly used in combination with chemotherapy to treat some types of breast cancer. It can cause inflammation in your mouth and gastrointestinal tract along with fatigue and nausea.

These side effects can have an impact on your physical and mental health, including your ability to tolerate certain foods.

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What are the effects of appetite changes during cancer treatment?

Not everyone who undergoes cancer treatment experiences changes in their appetite, taste, and ability to tolerate foods. But if you do have these side effects, you may find it difficult to meet your nutritional needs.

This may lead to:

  • weight loss
  • nutrient deficiencies
  • low energy
  • muscle deterioration
  • dizziness

What’s more, the cancer process itself can increase your body’s need for certain nutrients, including protein. This can make it even more difficult to meet your daily calorie and nutrient requirements.

Though everyone’s cancer treatment experience is different, the following dietary tips and food recommendations may help. With the right nutrition, you may be able to maintain your weight and muscle mass, reduce your risk of nutrient deficiencies, and feel better overall.

What are the best foods to eat during cancer treatment?

If you’re undergoing cancer treatment and experiencing side effects such as nausea, diarrhea, and mouth sores, prioritizing the following foods could help you meet your nutrient needs.

Lean, protein-rich foods

Foods that are low in fat and high in protein may be easier to tolerate than protein sources that are high in fat, especially if you’re experiencing nausea and diarrhea.

You can try:

  • chicken breast
  • ground turkey
  • scrambled eggs
  • lower fat Greek yogurt
  • plain tofu

Protein shakes and smoothies

Shakes and smoothies are an excellent way to take in calories and protein, and you can customize them based on your preferences and dietary needs. They can also be soothing and easy to tolerate if you have treatment-related mouth sores.

Plus, if you’re feeling nauseated and cannot tolerate solid foods, sipping on smoothies and shakes throughout the day can help you keep up with your calorie and nutrient needs.

If you’re concerned about weight loss, you can add ingredients such as peanut butter and protein powder to increase the calories in an easy-to-digest way. But always check with your oncology team or dietitian first.

Soups and soft foods, maybe through straws

Soup can be a good choice if you’re experiencing mouth sores, as long as it’s not too hot. Soups can help you stay hydrated and are easy to tolerate.

You can make soups with high calorie, high protein ingredients such as chicken, collagen peptides, and cream to help you take in a little extra nutrition, even when you don’t have much of an appetite.

Plus, you can add antioxidant-rich vegetables to your soups to support your overall health.

As long as they’re not too hot, you can use a straw to eat foods such as soup, applesauce, and smoothies to avoid aggravating mouth sores.

Bland foods

When you’re experiencing nausea or diarrhea, bland foods like white rice, toast, and pretzels may help soothe your stomach.

Alternatively, if you’re experiencing taste changes, you may want to add extra seasoning or flavorful ingredients such as lemon juice to your meals to make foods more palatable.

Manage your food intake

If you have less of an appetite or find eating to be difficult, eating several small meals throughout the day can help you get the calories you need without making food feel like too much of a chore.

Explore topical medications

There are also topical medications available to help ease the pain of mouth sores while you’re eating.

These include:

  • antiseptic gels and mouth rinses
  • fluocinonide gel
  • anti-inflammatory amlexanox paste
  • chlorhexidine gluconate mouthwash
  • steroid ointments such as triamcinolone

Personalize your diet

Keep in mind that everyone undergoing cancer treatment has a different experience, and not everyone will need to make drastic changes to their diet.

If you can, follow a well-rounded, nutrient-dense meal plan during cancer treatment. Prioritize foods that are high in protein and anti-inflammatory and antioxidant compounds.

These include:

  • fruits
  • vegetables
  • fish
  • nuts
  • legumes

These foods can help support your overall health and energy levels while you’re undergoing treatment.

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What foods should you avoid during cancer treatment?

Depending on the treatment-related side effects you experience, you may not be able to tolerate certain foods. For example, the foods listed below can irritate mouth sores and may worsen diarrhea and nausea.

Fried, greasy, and fatty foods

If you’re experiencing nausea or diarrhea, high fat foods could make your symptoms worse.

Foods and drinks that can irritate mouth sores

Acidic foods such as citrus fruits and juices, spicy foods, and tomato products can be uncomfortable to eat if you have mouth sores. The same goes for crunchy and sharp foods.

Foods that can worsen diarrhea

If you have diarrhea, eating foods that are high in fiber (such as beans and raw vegetables) and foods that contain certain ingredients (such as sugar alcohols) could worsen your symptoms.

Consult your team

These are general tips that may help you deal with common side effects related to cancer treatment. Your doctor and other health professionals can give you comprehensive dietary recommendations specific to your needs and symptoms.

Other diet tips for navigating cancer treatment

Your symptoms and ability to tolerate foods may change as your treatment progresses. This means you may have to change your diet several times during your treatment.

Talk with a dietitian

Your doctors and specialists, including a registered dietitian, can guide you through the process and make recommendations to support you in meeting your daily nutritional needs.

Consider supplementation

In addition to dietary changes, healthcare professionals may recommend dietary supplements such as vitamins, minerals, and protein to help you feel your best and reduce your risk of developing deficiencies.

They may also recommend prepared shakes such as those from Ensure or Boost.

Protect against foodborne illnesses

When undergoing cancer treatments such as chemotherapy, you have an increased risk of developing foodborne illnesses. For this reason, it’s important to avoid foods that have a high risk of contamination.

The National Cancer Institute recommends avoiding:

  • leftovers that have been in the refrigerator longer than 3 days
  • raw fish and shellfish
  • unpasteurized milk
  • runny eggs
  • raw nuts
  • leftover rice
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Your medical team can help

If you’re experiencing treatment-related side effects that are making it difficult for you to take in enough calories, it’s important to talk with your medical team right away.

They can give you helpful tips for dealing with nausea, diarrhea, and other symptoms and can recommend recipes, supplements, and other products that can help you feel better and make it easier for you to maintain a well-rounded diet.

Medically reviewed on December 14, 2023

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About the author

Jillian Kubala, MS, RD

Jillian Kubala is a registered dietitian based in Westhampton, NY. Jillian holds a master’s degree in nutrition from Stony Brook University School of Medicine as well as an undergraduate degree in nutrition science. She runs a private practice based on the east end of Long Island, NY, where she helps her clients achieve optimal wellness through nutrition and lifestyle changes.

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