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.
One study showed that using vitamin A, E, and beta carotene supplements may increase your risk of premature death.1 Further study is needed to look at the effects of these antioxidants as well as vitamin C and selenium. It is best to obtain antioxidants from a healthy diet.
What are antioxidants used for?
People use antioxidants to help treat or prevent some medical conditions, such as coronary artery disease (CAD), some cancers, macular degeneration, Alzheimer's disease, and some arthritis-related conditions.
The treatment of CAD with antioxidant supplements as well as with traditional medicine continues to be researched. Some experts believe antioxidant vitamins may help in treating CAD, although so far studies have not proved this.
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 supplements. Taking supplements in high doses can be harmful. No single antioxidant alone can protect the body. Most people should eat 5 to 9 servings of fruits and vegetables each day.
The U.S. Food and Drug Administration (FDA) does not regulate dietary supplements in the same way it regulates medicines. A dietary supplement can be sold with limited or no research on how well it works.
Always tell your doctor if you are using a dietary supplement or if you are thinking about combining a dietary supplement with your conventional medical treatment. It may not be safe to forgo your conventional medical treatment and rely only on a dietary supplement. This is especially important for women who are pregnant or breast-feeding.
When using dietary supplements, keep in mind the following:
- Like conventional medicines, dietary supplements may cause side effects, trigger allergic reactions, or interact with prescription and nonprescription medicines or other supplements you are taking. A side effect or interaction with another medicine or supplement may make your health worse.
- How dietary supplements 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 dietary supplements are not known.
- Bjelakovic G, et al. (2007). Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: Systematic review and meta-analysis. JAMA, 297(8): 842–857.
Other Works Consulted
- Vitamin supplements (2005). Medical Letter on Drugs and Therapeutics, 47(1213): 57–59.
- Murray MT, Bongiorno PB (2006). Flavonoids: Quercetin, citrus flavonoids, and hydroxyethylrutosides. In JE Pizzorno Jr, MT Murray, eds., Textbook of Natural Medicine, 3rd ed., pp. 967–973. Edinburgh: Churchill Livingstone.
- Ronzio RA (2006). Naturally occurring antioxidants. In JE Pizzorno Jr, MT Murray, eds., Textbook of Natural Medicine, 3rd ed., pp. 1085–1111. Edinburgh: Churchill Livingstone.
|Associate Editor||Pat Truman, MATC|
|Primary Medical Reviewer||Kathleen Romito, MD - Family Medicine|
|Specialist Medical Reviewer||Marc S. Micozzi, MD, PhD - Complementary and Alternative Medicine|
|Last Updated||June 30, 2009|
Last Updated: June 30, 2009