Antioxidants are simply molecules that slow down or prevent the oxidation of cells in the body. A low level of antioxidants in your body can cause oxidative stress and may damage or even kill off cells. Many diseases and illnesses, such as cancer, stroke and heart disease, are believed to be directly effected by the level of oxidative stress in a person's body. Therefore, antioxidants are important because they help to neutralize the free radicals in your body to prevent the oxidation of cells. Lab testing have shown that antioxidants are just as effective as their natural counterparts. Natural foods contain ranges of antioxidants that work together. These combinations of antioxidants in supplement form are much more effective.