From the preceding posts, it should be clear that free radicals generally cause deleterious effects, although there are a minority of beneficial ones too. The previous post has also highlighted the fact that the body has several antioxidant systems in place to counter the potential damage.
Sometimes the body will even go to dangerous lengths to boost its innate antioxidant capacities, and if you'll permit me a brief digression, I'll mention two candidates. Take the example of uric acid, the final breakdown product of purine (i.e. adenine and guanine) metabolism. Most mammals can break down uric acid further, but we humans have lost this ability. This could simply be an evolutionary error, of course, but there is another possibility. It turns out that uric acid is a very good antioxidant, and some researchers hypothesise that we have lost the ability to break it down on purpose so that the body's antioxidant systems are thereby boosted. The downside of our abnormally high uric acid levels is that in some people the substance is deposited in joints and tendons, provoking an inflammatory response: namely, gout.
This example doesn't stand alone. There are schools of thought that claim a similar rationale behind the high levels of bilirubin in neonates - bilirubin is a very good antioxidant too, and neonates need good antioxidants as they make the transition to a life of high oxygen concentration outside the uterus. Of course, in a few cases the hyperbilirubinaemia can cause the neonate to develop kernicterus, but this might be a price evolution is willing to pay for all those other babies that are saved oxidative damage to their tissues.
And so on. Even if the above two interesting but contentious hypotheses turn out to be wrong, the fact still remains that the body undeniably works to reduce free radicals in the majority of instances. So, since the body seems quite keen on its own antioxidant systems, it seems intuitively likely that taking additional antioxidants as supplements might be beneficial. On the face of it, those annoying adverts boasting the strong antioxidant effects of product X might have a kernel of truth about them.
Of course, shrewd reasoning and clever hypotheses aren't enough - we must look at what the actual data says. That'll be the topic of the next post.