Antioxidants have proven effective in fighting the free radicals. But they are not without their share of controversy.
There are many types of antioxidants, and they do different kinds of work. What marketers of supplements never tell you is that not all of it is good work. Antioxidants can certainly deactivate free radicals in a test tube, but in the human body they can sometimes have the opposite effect—acting as pro-oxidants instead of antioxidants.
As an example, studies show that smokers (those smoking a pack a day or more) who take Beta Carotene or Vitamin A supplements were at a higher risk for developing lung cancer and a higher risk of dying. The study showed 18% more lung cancer and 8% more deaths in male smokers who took 20mg of Beta Carotene.
Why are smoking and Beta Carotene pills a dangerous mix? Beta carotene is oxidized as it inactivates the free radicals from cigarette smoke, and its antioxidant capacity is "used up." In the process, it can turn into a pro-oxidant or form oxidized by-products, particularly if adequate amounts of vitamins C and E aren't present. It's well known that C and E work together to maximize their antioxidant effect. Recent research strongly suggests that these vitamins can also help limit the oxidation of beta carotene so that it won't damage cells. (In fact, any antioxidant can become a pro-oxidant under certain conditions in the body—especially if other antioxidants are lacking, since they protect one another from oxidation.)