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What Are They, Where Can You Find Them, And How Can They Affect Your Cancer

Like any popular buzzword, the meaning of the term “antioxidant” has been lost in recent years. Nutrition supplements and products have made bold claims regarding the power of antioxidants, ranging from cancer remission to cancer prevention. However, recent research indicates that antioxidant supplementation may actually lessen the efficacy of chemotherapy and radiation, raising questions as to what supplements and foods are safe during treatment. It is important to understand what antioxidants are, where you can find them, and how best to incorporate them into a overall healthy lifestyle both before, after, and during cancer treatment.

What Is An Antioxidant?

An antioxidant is a substance that balances a free radical by donating an electron to the otherwise unstable molecule. The free radical has lost an electron in its outer shell due to oxidation, and the stability provided by the antioxidant decreases the chances of cell damage due to oxidation.

Free radicals are caused by environmental factors like pollution as well as innate factors like stress. It is the role of the antioxidants in your body to track down the free radicals and stabilize them before any damage can be done.

Cell culture and animal studies have indicated that antioxidants can slow the spread of cancer, however results in human studies have been inconclusive and at times contradictory.

Where Can I Find Antioxidants?

Common antioxidants present in foods include beta-carotene, lycopene, vitamin C, vitamin E, and vitamin A, and lutein. There are many other antioxidants that occur less frequently (various flavonoids such as resveratrol, found in red wine), as well as a variety of substances that express antioxidant-like capabilities, but are not technically defined as antioxidants (capsaicin in chili peppers).

Antioxidant Food Sources
Beta-carotene Broccoli, Kale, Spinach, Sweet Potato, Carrots, Red/Yellow Bell Peppers, Apricots, Cantaloupe, Mango
Lutein Kale, Spinach, Broccoli, Zucchini, Brussels Sprouts, Peas, Collard Greens
Lycopene Tomatoes, Watermelon, Grapefruit, Asparagus, Red Cabbage, Carrots, Parsley
Vitamin C Spinach, Asparagus, Tomatoes, Pineapple, Cantaloupe, Citrus Fruits, Berries, Green Peppers, Brussels Sprouts, Broccoli, Watercress, Red/Yellow Bell Peppers, Mango, Papaya, Guava
Vitamin E Olive/Soybean/Corn/Cottonseed Oil, Nuts/Nut Butters, Whole Grains, Wheat, Brown Rice, Oatmeal, Sweet Potatoes, Beans, Lentils, Dark Leafy Green Vegetables
Vitamin A Sweet Potatoes, Spinach, Carrots, Pumpkin, Red/Yellow Bell Peppers (*animal products such as liver as also high in vitamin A)


Outside of plant-based foods, antioxidants are also sold as dietary supplements in liquid, capsule, or powder form. There is a common belief that “more is better,” driving people to consume mega-doses of an antioxidant in a pill form rather than through natural food sources. However, there are few supplements that are recommended in place of foods, and supplementation should only be used when you are unable to consume a diet comprised of a wide variety of fruits and vegetables. This may be the case during treatment due to taste changes or nausea, and those specific cases should be discussed with your treatment specialists.

Antioxidants and Cancer: What You Need To Know

Balanced nutrition is key to maintaining health before, during, and after cancer treatment. Chemotherapy and radiation can be taxing for the body’s systems, and dedicating yourself to healthy eating can help with recovery. However, it can be difficult to maintain or begin a healthful diet due to either the side effects of treatment or the stress related with managing your diagnosis.

The best way to approach antioxidants in your diet is to eat a wide array of the foods listed above. Choose products that are local and seasonal when possible. Remember to include all colors of the rainbow, and emphasize the plant-based foods.

If the side effects of treatment make it impossible for you to consume a balanced diet of antioxidant-rich plant foods, then you may consider taking a dietary supplement. However, keep these tips in mind:

  • Avoid supplements in mega-doses. Look at the labels for supplements that contain only 100% of the DV.
  • Avoid taking any antioxidant supplement right before receiving chemotherapy or radiation treatment. Research has found that antioxidants can actually lessen the efficacy of chemotherapy and radiation treatments.
  • If you are taking any kind of supplements, bring the label/packaging in to a registered dietitian or nutrition specialist where you are being treated to ensure it doesn’t contain any additional ingredients that are contraindicated during treatment.

For additional information:

National Institutes of Health, Office of Dietary Supplements

National Institutes of Health, National Cancer Institute: Antioxidants and Cancer Prevention Fact Sheet

American Cancer Society: Dietary Supplements

About the Author: Katie Andrews, MS, is a graduate of the Nutrition Communications program at the Friedman School of Nutrition Science and Policy at Tufts University. She is passionate about communicating sound nutrition advice to consumers and uses her blog,, as a platform to discuss nutrition news and research. She spent a year working with the dietitians at Dana Farber Cancer Institute in Boston, MA and will be completing her dietetic internship at Massachusetts General Hospital this fall. She has also written for Eating Well and the National Strength and Conditioning Association Journal. She is an avid spin instructor at Recycle Studio in Boston’s South End and you can find her popular playlists on her blog.