Our food and drinks are chock-full of antioxidants nowadays, along with promises of protection from illness and even faster recovery when you've taken ill. US News explains that antioxidant studies show hardly conclusive data, and what we think heals us isn't really doing much at all.
First, it's important to understand what antioxidants do. Charles H. Brown, writing for US News, explains:
The body generates hundreds of substances called "free radicals" when converting food to energy. Other free radicals are extracted from food or breathed in from the air, and some are generated by the sunlight's action on the skin and eyes. Once formed, these toxic compounds can start a chain reaction like dominoes. Cells may function poorly or die. Resulting oxidative stress is associated with more than 200 diseases. The scavenger-free radical molecules are missing an electron in their outer shells and will do anything to fill them, including stealing electrons from your body's cellular structures. Such cellular thievery may damage DNA, proteins (enzymes), and cell membranes. When these cells are damaged, your body is damaged, creating the foundation for disease and accelerated ageing.
Antioxidants are molecules which can safely interact with free radicals and terminate the chain reaction before vital molecules are damaged. Although there are several enzyme systems within the body that disarm free radicals, the principal antioxidants are vitamin E, beta-carotene, vitamin C, and selenium. When these antioxidants neutralize free radicals by donating an electron particle, they are left with a small problem. The antioxidants are now missing an electron and have become free radicals themselves. The body cannot manufacture these antioxidants, so they must be supplied in your diet.
While antioxidants can help in theory, no studies with any conclusive evidence of disease prevention were found. At best, they seemed to help slow "age-related macular degeneration", and nothing more. Currently, the benefits of antioxidants don't appear helpful in most cases, and they certainly won't cure an illness like many would like to believe. If you're spending extra money to have them in your daily diet, you might want to reconsider.
Do You Really Need Antioxidants? [US News]