Cells in our bodies can be damaged by oxidative stress, any chemical process that creates reactive oxygen species. The damaged cells can be repaired by autohealing processes; however, if the self-repairing process malfunctions either by means of genetic or environmental influences, the cells is still in an irrecoverable state which can lead to many diseases depending on the area of the damaged cells. Antioxidants are substances that after taking will stop the reactive oxygen species from harming the cells because of a special property that they can chemically bound to the reactive oxygen molecules and form innoxious molecules.

Examples of antioxidants are beta-carotene, lutein, lycopene, selenium, vitamin A, vitamin C, and vitamin E.