Topic Overview

What are antioxidants?

Antioxidants protect the body from damage caused by harmful molecules called free radicals. Many experts believe this damage is a factor in the development of blood vessel disease (atherosclerosis), cancer, and other conditions.

You are exposed to free radicals:

  • Through by-products of normal processes that take place in your body (such as the burning of sugars for energy and the release of digestive enzymes to break down food).
  • When the body breaks down certain medicines.
  • Through pollutants.

Antioxidants include some vitamins (such as vitamins C and E), some minerals (such as selenium), and flavonoids, which are found in plants. The best sources of antioxidants are fruits and vegetables. You can find flavonoids in fruits, red wine, and teas. You can also buy antioxidant supplements. It is best to obtain antioxidants from a healthy diet.

What are antioxidants used for?

Antioxidants may play a role in managing or preventing some medical conditions, such as some cancers, macular degeneration, Alzheimer's disease, and some arthritis-related conditions.

Are antioxidants safe?

Until more studies are done, it is best to get your antioxidants from a diet rich in fruits and vegetables rather than from natural health products. Taking natural health products in high doses can be harmful. No single antioxidant alone can protect the body. Most people should eat 7 to 10 servings of fruits and vegetables each day.

The Natural Health Products Directorate (NHPD), within the Health Products and Food Branch of Health Canada, regulates natural health products in Canada. Natural health products, including antioxidant supplements, must be reviewed and approved by the NHPD before they can be sold in Canada.

Always tell your doctor if you are using a natural health product or if you are thinking about combining a natural health product with your conventional medical treatment. It may not be safe to forgo your conventional medical treatment and rely only on a natural health product. This is especially important for women who are pregnant or breastfeeding.

When using natural health products, keep in mind the following:

  • Like conventional medicines, natural health products may cause side effects, trigger allergic reactions, or interact with prescription and non-prescription medicines or other natural health products you are taking. A side effect or interaction with another medicine or natural product may make your health worse.
  • How natural health products are manufactured may not be standardized. Because of this, how well they work or any side effects they cause may differ among brands or even within different lots of the same brand. The form of a supplement that you buy in health food or grocery stores may not be the same as the form used in research.
  • Other than for vitamins and minerals, the long-term effects of most natural health products are not known.

Related Information


Other Works Consulted

  • Murray MT (2013). Flavonoids: Quercetin, citrus flavonoids, and hydroxyethylrutosides. In JE Pizzorno, MT Murray, eds., Textbook of Natural Medicine, 4th ed., pp. 772–779. St. Louis: Elsevier.
  • Ronzio RA (2013). Naturally occurring antioxidants. In JE Pizzorno, MT Murray, eds., Textbook of Natural Medicine, 4th ed., pp. 891–914. St. Louis: Elsevier.


ByHealthwise Staff
Primary Medical Reviewer Adam Husney, MD - Family Medicine
Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Kathleen Romito, MD - Family Medicine

Current as ofMay 22, 2015