What exactly are antioxidants? Antioxidants include some vitamins and minerals, but to appreciate the value of antioxidants, you first need to understand the potential dangers of free radicals, a form of oxygen that has been chemically modified into a highly unstable substance.
Free radicals are unstable because they are missing electrons, which must be replaced. So they seek out other compounds in the body and steal electrons to restore stability. If the compound giving up its electrons is the fat and protein in an LDL-cholesterol molecule, the result is the formation of fatty lesions in the walls of the blood vessels -- the hallmark of atherosclerosis.
Although the body has a means of handling a normal burden of free radicals, many of the forces that cause free radicals to form cannot be stopped. For instance, they form in the normal course of the day, just by our breathing in oxygen. (Obviously, it's impossible to avoid this type of free radical because we have to breathe.)
Yet the production of free radicals is not always a bad thing. They are part of the immune system and help fight off infection. (During cancer treatment, the free radicals produced help to destroy cancer cells.) Antioxidants are the armament the body uses for protection against damage from free radicals. It is when the production of free radicals overwhelms the body's protective system of antioxidants that disease-producing damage results.
The heart and the blood vessels, like the lungs, are especially vulnerable to the effects of oxygen because their exposure to this element is so great. The blood is the route of transport for oxygen throughout the body. The blood is also the route of transport for many of the substances that can act on oxygen to produce free radicals.
Cholesterol is carried through the blood, packaged in LDL particles; LDL is responsible for depositing cholesterol in the walls of the arteries. These deposits form the fatty plaques that eventually narrow the arteries, possibly leading to a heart attack. Scientists now know that before LDL cholesterol can have this effect, it first has to be modified by a free radical to form an oxidized LDL.
In other words, the free radical substances produced in the blood from oxygen by any one of a number of causes -- like chemicals from cigarette smoke or environmental pollution -- can set off a chain of events that generates oxidized LDL cholesterol and ultimately can lead to heart disease.