What do free radicals have to do with aging?

If one believes that free radicals bring about aging and disease, then it stands to reason that we could live longer, healthier lives by either eliminating their presence altogether or by investing in mechanisms that will make them disappear. Because free radicals are a natural byproduct of numerous bodily functions, including breathing, the former is impossible. We're doomed to have these molecules that could lead to our demise running around in our body. So what are scientists doing about the latter option?

The main point of defense for many years has been antioxidants, so much so that we might as well retire the phrase "an apple a day keeps the doctor away" and consider something along the lines of "a lot of antioxidants keep free radicals away." Antioxidants, such as beta carotene and vitamins C and E, help to clean up and neutralize free radicals. That's why you see antioxidants' presence touted on everything from dietary supplements to skin cream. The thinking goes that if you consume large amounts of these antioxidants, then you prevent oxidative damage and provide an important back-up for the superoxide dismutase (SOD) that weakens with age.

However, antioxidants haven't proven to be the fountain of youth that some scientists were hoping for. For one thing, antioxidants have failed to demonstrate consistent protective benefits in medical studies, particularly in the case of women [sources: Wanjek; Angier]. Additionally, the human body strives for a state of balance, or homeostasis, and by ramping up the antioxidants, particularly in a bulk supplement form, you could actually damage the natural mechanisms for dealing with free radicals [source: Angier].

Some researchers, in a study published in Science magazine in 1994, attempted to tweak those natural mechanisms directly. SOD keeps free radicals in check by converting them to hydrogen peroxide, and then another enzyme, catalase, converts the hydrogen peroxide to water, which is what much of the human body is made of [source: Kolata]. When researchers endowed fruit flies with the ability to produce excess amounts of both SOD and catalase, the flies lived longer, more vigorous lives than their non-enhanced counterparts [source: Kolata].

Of course, there's a huge difference between a fruit fly and a human, so more work needs to be done on the role of free radicals and aging. Scientists hope that eventually, we'll be able to take a pill that battles free radicals, but until then, we're stuck remaining healthy and fighting free radicals the old-fashioned way: regular exercise, no cigarettes and a healthy diet.