Unfortunately, the ever-bogus 'alternative' health field have pushed "antioxidants" as being some sort of wonderous protector against a vast variety of ailments, from heart disease to Alzheimer's disease to ADHD, and beyond. For once, this isn't intrinsically silly: this post deals with a theoretical argument in favour of antioxidant supplements.
However, our current state of research simply doesn't support this practice. Most well conducted research indicates that antioxidant supplements offer no additional benefits, and may even increase the rates of certain cancers in some instances. Whilst a little counterintuitive, this conclusion has a broad base of evidential support, as this post demonstrates, and this post confirms.
The above two posts were preceded by some of the interesting theory behind free radicals, the substances that antioxidants protect against. The natural starting point was to ask, and answer, the question of what free radicals are, and how they are formed. From that knowledge base, we could look at the type of damage free radicals are capable of, and then what the body attempts to do about their often pernicious effects.
Of course, evolution is incredibly resourceful, and has even managed to turn the dangers of free radicals into advantages, in a selected few cases. This post summarises them.