By curbing their activity, you can slow down the very processes in your body that cause disease and aging. Today, people continuously subject themselves to many things that increase the level of free radicals in their bodies and so the body can easily become overpopulated with oxygen-derived species that upset cell biochemistry. This imbalance of free radicals in the body is called oxidative stress. Just as oxidation takes place all around us, it also occurs in our bodies. There are millions of chemical reactions involving oxidation taking place in our bodies every second.
Free radicals are unstable molecules.
They often contain oxygen. They are unstable because they have only one electron and they desperately want two to make them stable. To get another electron they rob one from anything they can. Healthy cells in our bodies are a good mark for them. They do this relentlessly and very quickly, and can cause a lot of damage.