Radical solutions: protect your health with antioxidants.

You could be walking down the street when it hits you. An invisible molecule of, say, air pollution enters your body. It ricochets around inside you, chewing up genes. Years later, seemingly out of nowhere, you're diagnosed with cancer.

Called free radicals, these invaders are a big reason you age and develop degenerative diseases such as cancer and heart disease.

Normally, electrons--negatively charged particles--come in pairs. But when an atom is short one electron, or has one too many, it's called a free radical.

It's "free" in the sense that, being unpaired, it's aggressively seeking a mate--and it is likely to steal an electron from one of your normal cells. Losing an electron damages either the exterior membrane or the contents of the cell. Called oxidation, this is the same process that turns iron rusty, butter rancid and bananas brown.

A host of magazine articles have given any oxidation a bad name. But in limited quantities, oxidation can be beneficial: It generates energy and kills bacterial invaders.

An excess of free radicals, however, creates problems. If a free radical picks up an electron from one of your DNA atoms, then part of your DNA has been damaged.

But DNA reproduces itself, right? Yes, but when damaged DNA replicates, it doesn't make normal DNA. Instead, it mutates; it creates more damaged DNA--which makes more damaged DNA, and so on. It's the process we know as cancer and aging.