Free radicals are highly reactive atoms that have an unpaired electron. They are generated as a normal by product of many different chemical reactions in the body and are strong oxidizing agents. T
hey damage cell membranes, proteins, enzymes, lipids and DNA, and they are believed to play important roles in cancer, aging, atherosclerosis, and autoimmune diseases. Ascorbic acid (vitamin C) is called an antioxidant because it inactivates free radicals and protects against oxidative damage.
Other antioxidants present in human blood include uric acid, alpha-tocopherol, ubiquinol-10, bilirubin and beta-carotene. A study was performed to evaluate the effectiveness of these antioxidants in protecting blood proteins and lipids (fats) from oxidative damage. Blood samples from human volunteers were exposed to free radicals from three different sources: AAPH (a chemical that causes free radicals to form); cigarette smoke; and activated neutrophils (white blood cells that produce oxygen radicals).
When the blood samples were exposed to these substances, ascorbic acid protected blood proteins and lipids, including low-density-lipoprotein (a lipid that carries cholesterol in the blood), from oxidative damage. However, when ascorbic acid was removed from the blood, the blood proteins and lipids were oxidized. When ascorbic acid was again added to the blood, oxidation stopped. These results indicate that ascorbic acid protects the blood from oxidation caused by free radicals, and that ascorbic acid is one of the most potent antioxidants in the blood. Further research may determine whether vitamin C can be used to prevent degenerative diseases that are caused or worsened by oxidative stress. (Consumer Summary produced by Reliance Medical Information, Inc.)