Antioxidants are molecules that limit oxidative damage caused by reactive oxygen species, such as free radicals, that arise from normal metabolism, inflammation, pollution and radiation. These reactive molecules can damage lipids, proteins and DNA, which links oxidative stress to aging and many diseases. Antioxidants work mainly by donating electrons to neutralize reactive species or by helping repair and remove damaged molecules.

The body produces its own antioxidant defenses, including enzymes like superoxide dismutase, catalase and glutathione peroxidase, as well as small molecules such as glutathione, uric acid and bilirubin. Diet supplies additional antioxidants. Well known examples include vitamin C, vitamin E, carotenoids such as beta carotene and lycopene, and polyphenols such as flavonoids and resveratrol. These compounds are abundant in fruits, vegetables, nuts, seeds, whole grains, tea and coffee.

Evidence from cell and animal studies shows that antioxidants can protect against oxidative damage and may reduce risk markers for cardiovascular disease, cancer and neurodegenerative disorders. However, large clinical trials of high dose antioxidant supplements often fail to show clear benefits and in some cases suggest possible harm, such as increased mortality or higher cancer risk with certain beta carotene supplements in smokers. This indicates that antioxidant effects depend on dose, chemical form, context and the complex balance between oxidants and antioxidants in living systems.

Current research emphasizes obtaining antioxidants from varied, plant rich diets rather than relying on high dose single nutrient supplements, and on understanding how redox balance, rather than simply “more antioxidants,” influences health and disease.