The definition of antioxidant is "any substance that can effectively inhibit the oxidation reaction of low-concentration free radicals", and its mechanism of action can be to directly act on free radicals or indirectly consume substances that are easy to produce free radicals to prevent further reactions.

When the human body inevitably produces free radicals, it also naturally produces antioxidant substances that resist free radicals to offset the oxidative attack of free radicals on human cells.