Free radicals, also known simply as radicals, are organic molecules responsible for aging, tissue damage, and possibly some diseases. These molecules are very unstable, therefore they look to bond with other molecules, destroying their health and further continuing the damaging process. Antioxidants, present in many foods, are molecules that prevent free radicals from harming healthy tissue.
Radicals do play a key role in several biological processes. They play a part in the work of the white blood cells called phagocytes, which "eat" bacteria and other pathogens in the body. They also are believed to be involved in a process called redox signaling, where they are thought to act as cellular messengers.
The Problem with Radicals
Some molecules are unstable. They do not have an even number of electrons, so they are always searching for an extra electron they can "steal" to become stable. Out in the world, this is a normal process, but in the body, it can result in unnecessary and unwanted damage.
Free radicals are "free" because they float around until they stabilize, and "radical" in the sense that there are a wide variety of molecules from which they can take an electron. The damage doesn't stop there, however, as the new molecule, say a piece of a cell wall, is now also missing an electron and has become another free radical. This snowball effect can wreak havoc on healthy tissue.
How Antioxidants Can Help
One way to feed the hungry electron-appetite of free radicals is to eat more antioxidants. Antioxidants are molecules found in fresh foods like vegetables and fruits, particularly in the vitamins found in these foods, including A, E, and beta-carotene. These molecules act like a giant boulder in the path of the snowball, stopping free radicals from causing untold damage. It's better to get antioxidants from a balanced diet, rather than vitamin supplements, because the body can more easily absorb them.
Some processes brought about by free radicals are inevitable, such as aging, but others can be prevented, like destruction of DNA or clogging of arteries. Free radicals are created by environmental pollution, cigarette smoking, and poisons like cleaners or herbicides. Their role in certain types of cancer, strokes, and heart disease is still being investigated. Preliminarily, low concentrations of free radicals have been associated with a reduced risk for heart disease and stroke, but more studies are needed to understand their relationship.