Survivorship: During and After Treatment

Benefits of Good Nutrition During Cancer Treatment

Eating to get the nutrients and calories you need is not usually a problem when you're healthy. But when you’re being treated for cancer, this can be hard, especially if you have side effects or just don’t feel well. Here are some ways to get the nutrients you need and the reasons you need them.

Why eating well during treatment is important

Many people with cancer become malnourished. This is because cancer can increase your metabolism but decrease your appetite at the same time. In addition, side effects from treatment like mucositis, diarrhea, nausea, and taste changes can make it harder to eat.

Eating well while you’re being treated for cancer might help you:

  • Feel stronger
  • Keep up your energy
  • Maintain your weight and your body’s store of nutrients
  • Better tolerate treatment-related side effects
  • Lower your risk of infection
  • Heal and recover faster

Without the food and nutrients you need, it can be harder to tolerate your cancer treatment. It’s important to plan how you will get these nutrients and deal with the side effects of your treatment.

Understanding what nutrients you need

Eating well means eating the right foods to get the nutrients your body needs to fight cancer. These nutrients include proteins, fats, carbohydrates, water, vitamins, and minerals.

You need protein to grow, repair body tissue, and keep your immune system healthy. If your body doesn’t get enough protein, it might break down muscle for fuel. This can slow your ability to recover from illness and lower your resistance to infection.

People with cancer often need more protein than usual. After surgery, chemotherapy, or radiation therapy, extra protein is often needed to heal tissues and help fight infection.

Protein sources include fish, poultry, lean red meat, eggs, low-fat dairy products, nuts and nut butters, dried beans, peas and lentils, and soy foods.

Carbohydrates are your major source of energy for physical activity and normal functions.

The best sources of carbohydrates – fruits, vegetables, and whole grains – also supply the vitamins, minerals, and fiber your body needs. Fiber helps move food waste out of your body and binds with water in the stool to help keep it soft.

Other sources of carbohydrates include bread, potatoes, rice, pasta, [HM1] [BG2] [BL3] grains, cereals, corn, peas, and beans. Sweets (desserts, candy, and drinks with sugar) can supply carbohydrates and calories, but they have few vitamins, minerals, or fiber.

Fats and oils are other sources of energy. Your body can use fats to store energy, insulate body tissues, and transport some vitamins through your blood.

Some fats are healthier than others.

  • Try to get most of your fat calories from monounsaturated and polyunsaturated fats.
  • Get no more than 10% of calories from saturated fats as they can raise cholesterol and your risk for heart disease.
  • Avoid trans fats which come from partially hydrogenated vegetable oil. These largely have been removed from the food supply in the US.

Water and other liquids are vital to your health. If you don’t take in enough liquids or lose too much through vomiting or diarrhea, you can become dehydrated. This is when your body doesn’t have as much fluid as it needs.

To keep from being dehydrated, you should try to drink at least four 8-ounce glasses of liquid each day. You may need extra fluids if you’re vomiting, have diarrhea, or even if you’re just not eating much. Water is the best choice, but all liquids (soups, milk, even ice cream and gelatin) count toward your goals. Eating fruits and vegetables that contain a lot of water, such as lettuce, cucumbers, or melons, can also help.

Your body needs certain vitamins and minerals to function properly. You can most often get what you need by eating a healthy diet. But it can be hard to eat a balanced diet when you’re being treated for cancer, especially if you have certain side effects.

If you have trouble eating for several weeks or months because of the effects of cancer or treatment, be sure to tell your doctor. Your doctor or a registered dietitian (RD) might suggest that you take a daily multivitamin and mineral supplement. You might also need to have blood work done to check your vitamin or mineral levels.

If your doctor says it’s OK for you to take vitamins, look for a supplement with no more than 100% of the Daily Value (DV) of vitamins and minerals. Be sure to ask your doctor or RD if there are any vitamins or minerals that you shouldn’t take.

Supplements

Be sure to talk with your doctor first before taking any dietary supplements. Taking certain vitamins, minerals, herbs and other supplements can be harmful. In fact, taking large doses of some vitamins and minerals can make chemotherapy and radiation therapy less effective.

Antioxidants

Antioxidants help protect your body from free radicals, molecules that can damage normal cells. They include vitamins A, C, and E, selenium, and zinc. Your body also makes enzymes to protect from free radicals. The best way to get antioxidants is by eating fruits and vegetables. Antioxidant supplements are often not recommended while you’re getting cancer treatment.

Phytonutrients

Phytonutrients are compounds in plant-based foods that are thought to decrease the risk of chronic diseases, like cancer. Phytonutrients are found in plants such as fruits and vegetables, or things made from plants, like tofu or tea. It is best to get them by eating food rather than taking supplements or pills.

Herbs

Many herbal supplements claim to improve your health or fight disease, but it’s hard to know if they are safe and effective or can cause harmful side effects. Also, some herbal supplements can interfere with cancer treatments and recovery from surgery. They might also interact with other medicines you are given during cancer treatment. If you’re thinking about using products containing herbs, talk with your cancer doctor to make sure they won’t interfere with your treatment.

Preparing for Treatment with Good Nutrition

Eating well to get the nutrients you need before you start treatment can help prepare you for the effects of treatment. You’ll go into treatment with reserves to help keep up your strength, your energy level, and your ability to fight infection. A healthy diet can also keep body tissues from breaking down and build new tissues.

Planning can also help you continue eating well once treatment starts.  Talk to your cancer care team about how you might feel during treatment. Planning how you’ll cope with possible side effects can make you feel more in control and ready for the changes that may come.

Here are some tips to help you get ready:

  • Stock up with your favorite foods so you won’t need to shop as often. Include foods you know you can eat even when you’re sick.
  • Cook in advance and freeze food in meal-sized portions.
  • Ask your friends or family members to help with shopping and cooking. Be sure to tell them if there are certain things you have or might have trouble eating.
  • Ask your cancer care team if you are likely to have any problems eating. They can help you plan diet changes to help manage side effects like diarrhea, weight loss, swallowing problems, or nausea and vomiting.

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Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).

 

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Last Revised: October 13, 2025

Last Revised: October 13, 2025

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