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.
The “antioxidant hypothesis” states that herbs and supplements with antioxidant properties may prevent illnesses and health problems associated with excess free-radical activity. For example, the conditions heart disease, cancer, macular degeneration, and aging skinare just a few of the hundreds of illnesses in which free radicals are thought to play a role. Based on this hypothesis, some of the largest double-blind, placebo-controlled studies in history were set up and performed to evaluate the potential disease-preventive benefits of various antioxidant supplements. The results, unfortunately, have been quite disappointing.1-6At present, there is no firm evidence that antioxidants provide any meaningful health benefits. Indeed, in a 2012 review of 78 randomized trials involving 296,707 participants, researchers found no evidence that antioxidant supplements (eg, beta-carotene, vitamin A, vitamin C, vitamin E, selenium) could reduce mortality.8
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.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.