Antioxidants are substances that inactivate free radicals, highly unstable molecules that can damage cell membranes and scramble the genetic information (DNA) in cells. Free radicals are produced in the body during normal cell metabolism, and at a higher rate following tissue injury or exposure to tobacco smoke, sunlight, x-rays, and other environmental influences. To fight these dangerous chemicals, the body deploys a powerful antioxidant defense system, but it is hypothesized that in some cases the quantity of free radicals may overwhelm the body's natural defenses. This in turn could theoretically accelerate or cause various illnesses.
Vitamins A , C , and E , beta-carotene , and the mineral selenium function as antioxidants, agents with the ability to deactivate naturally occurring toxic compounds called free radicals . Other substances in foods such as lutein , astaxanthin and lycopene also have antioxidant activity; in addition, as noted above, the body produces its own antioxidants.
What is the reason for this discrepancy? It is possible that studies have not involved the right combinations of antioxidants. It is also possible that the antioxidant hypothesis is wrong.
For more information, see the individual articles on the antioxidant nutrients noted above.