Meaning of antioxidant: Antioxidants are substances that neutralize unstable molecules called free radicals, though supplement studies have not consistently shown they prevent disease.

Definition of antioxidant

An antioxidant is a substance that helps neutralize free radicals, unstable molecules produced during normal metabolism and by exposure to factors such as tobacco smoke and pollution, that can otherwise damage cells and their DNA over time.

The body produces some antioxidants naturally and also obtains others from food, including vitamins C and E, beta-carotene, and various plant compounds found in fruits and vegetables. Antioxidants work by donating an electron to a free radical, stabilizing it before it can damage nearby cellular structures.

Although free radical damage has been linked to aging and to conditions such as heart disease and cancer, large clinical trials testing high dose antioxidant supplements have generally not shown a clear benefit in preventing these diseases, and in some studies certain supplements have shown unexpected effects, which is why obtaining antioxidants through food rather than concentrated supplements is generally emphasized.

Used in a sentence

The patient asked about the potential benefits of antioxidant supplements after a cancer diagnosis.

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Good to know

Antioxidant rich foods and high dose antioxidant supplements are not equivalent, since clinical trials of concentrated supplements have not reliably shown the same benefit associated with antioxidant rich diets.

Word origin

Where “antioxidant” comes from

Formed from Greek anti-, meaning against, and oxys, meaning sharp or acid, the root underlying oxygen and oxidation.

For learning, not diagnosis. This glossary provides general educational information and is not a substitute for advice from a qualified healthcare professional. If you may be experiencing a medical emergency, contact local emergency services.