Antioxidant substances, such as vitamins and carotenoids, are thought to protect the body against the destructive effects of free radicals. Antioxidants neutralize free radicals by donating one of their own electrons, ending the electron-"stealing" reaction. They act as scavengers, helping to prevent cell and tissue damage that could lead to cardiovascular disease and cancer.

Oxidation of low-density lipoprotein (LDL) cholesterol is important in the development of fatty build-ups in the arteries (see Atherosclerosis). Antioxidant substances, such as vitamins and carotenoids, can potentially prevent LDL oxidation and its harmful effects.