Without factors that ultimately determine whether oxidative damage can be overcome, oxidative damage cannot be overcome, only prevented. When too many free radicals are present in the body, they attack macromolecules within the cell, such as proteins, lipids and deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), causing oxidative damage to the cell. This oxidative damage is the cause of many inflammatory reactions, as well as degeneration and aging. In order to prevent cells from being damaged by free radicals, the body has developed an antioxidant defense system against free radicals, so that free radicals do not jeopardize human health. Changes in oxidative stress in the body can be detected by the content and activity of antioxidants, the products of free radicals attacking macromolecules in the cells, and the content of free radical-producing enzymes. When oxidative stress rises in the body, a diet supplemented with vitamins and antioxidants, moderate exercise, and changes in poor lifestyle habits can be used to remove the factors in the body that are detrimental to health, in order to achieve the goal of reducing oxidative stress and preventing disease.