Supplement Use During Radiation Therapy

Author: Kristen D'Elia, BSN, RN, Carly Roop, RD, CSO, MA, LDN, Lauren Clanet, RD, CSO, LDN
Last Reviewed: February 02, 2023

What are supplements and what are they used for?

A supplement is a man-made product that can be used to provide nutrients like vitamins, minerals, or electrolytes. These nutrients are needed to keep your body working correctly. Examples of supplements are:

  • Vitamins.
  • Minerals.
  • Herbs or other botanical substances.
  • Amino acids.
  • Protein powder.

If you eat a balanced diet, supplements should not be needed. However, some people getting treatment for cancer may need supplements. Cancer treatments, the cancer itself, and not eating a balanced diet can affect the levels of these nutrients in your body.

Nutrient levels can be affected by medications, treatments, nutrition, and how healthy your body is. If you have levels that are lower than normal, your provider may tell you to take supplements.

Are supplements safe?

You should always check with your healthcare provider, pharmacist, or dietitian before taking any supplement. It is also important for your healthcare providers to know what you are taking. When asked to list your medications, include all vitamins, supplements, and over the counter medications. There are some things a person should think about before taking a supplement:

  • "Natural" does not always mean safe.
  • Most supplements in the United States do not need to be approved by the FDA like medications do.
  • Supplements may not have what the label says they do (some studies have found more than 60% do not).
  • They may have harmful ingredients, such as lead, arsenic, cadmium, and more.
  • Some supplements can change how medications and cancer treatments work. They may also affect how your organs work (such as liver function).

Supplement Use During Radiation Therapy

You should always check with your provider, pharmacist, or dietitian before taking any supplements. You should take them as directed. There are supplements that can interfere with your radiation treatment and there are also supplements that may help your treatment work better.


Antioxidants include vitamins A, C, E, beta-carotene, and selenium, among others. Antioxidants repair damage to cells and also prevent damage. Some studies show that when patients take high amounts of antioxidants, chemotherapy, and radiation will not work as well because the antioxidants will protect the cancer cells, along with healthy cells. While antioxidants do have their benefits, research has shown that supplements do not lower your risk of getting cancer or keep cancer from coming back (recurrence).

Fish Oil Supplements

Both fish oil and Omega-3 fatty acid supplements may lower the ability of your platelets to work, which can cause bleeding. Doses higher than 3 grams per day may increase bleeding and how long you bleed. Some patients getting treatment for cancer are already at a higher risk of bleeding. These supplements can also change how some platinum-based chemotherapies work (cisplatin, carboplatin). Patients taking fish oil should talk with their provider about whether or not to stay on the supplement during treatment.


Curcumin is found in the turmeric plant and can work as an anti-inflammatory. Research is showing that it can work as a radiosensitizer (can help make tumor cells more sensitive to radiation and easier to kill) and a radioprotector to normal cells (will protect normal, healthy cells). Challenges are that it can be poorly absorbed by the body and is eliminated (removed) by the body quickly. These factors limit how well it works. There are clinical trials studying the use of curcumin. Talk to your provider about these studies and if this supplement would be helpful to you. You should not take it without first talking to your provider.


Multivitamins are products that contain ingredients like vitamins and minerals. Often, they are used to supplement what you are not taking in through the food you eat and drink. If you eat a healthy diet, you often do not need to take a multivitamin. Your provider may tell you that it is ok to take a multivitamin during treatment. You should review the ingredients found in your multivitamin with your provider before continuing to take it.

There are many over-the-counter products that contain supplements. It is important that you read the labels of these products to know what they contain.

Key Takeaways for Patients Getting Radiation Therapy

  • You should not take any supplements without first talking to your provider, pharmacist, or dietitian.
  • Supplements may affect radiation treatment, other treatments, medications, organ function, and your health. Check with your provider.
  • The number of antioxidants found in foods is safe unless you are juicing a lot of fruits/vegetables daily (example: 15 pounds of produce juices per day).

Resources for Facts About Supplements

These websites offer helpful information about medications and supplements:


Antioxidants and Cancer Prevention. (2017, February 6). [cgvFactSheet].

Gröber, U., Holzhauer, P., Kisters, K., Holick, M. F., & Adamietz, I. A. (2016). Micronutrients in Oncological Intervention. Nutrients, 8(3).

Harvard School of Public Health. Should I take a daily multivitamin? (n.d.)

Memorial Sloan Kettering Cancer Center. About Herbs, Botanicals & Other Products.

Office of Dietary Supplements - Dietary Supplements: What You Need to Know. (2023).

Pirayesh Islamian, J., & Mehrali, H. (2015). Lycopene as A Carotenoid Provides Radioprotectant and Antioxidant Effects by Quenching Radiation-Induced Free Radical Singlet Oxygen: An Overview. Cell Journal (Yakhteh), 16(4), 386–391.

Should Supplemental Antioxidant Administration Be Avoided During Chemotherapy and Radiation Therapy? | JNCI: Journal of the National Cancer Institute | Oxford Academic. (2008). Retrieved October 25, 2018, from

Turmeric and Curcumin Supplement and Spices Reviews and Information. (n.d.).

Verma, V. (2016). Relationship and interactions of curcumin with radiation therapy. World Journal of Clinical Oncology, 7(3), 275–283.

Zoi, V., Galani, V., Tsekeris, P., Kyritsis, A. & Alexiou, G. (2022). Radiosensitization and Radioprotection by Curcumin in Glioblastoma and Other Cancers.


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