Antioxidants are molecules that slow or prevent the oxidation of other chemicals. Oxidation is a redox chemical reaction, that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can involve the production of free radicals, which can form dangerous chain reactions. Antioxidants can terminate these chain reactions by removing radical intermediates and can inhibit other oxidation reactions by being oxidized themselves. As a result, antioxidants are often reducing agents, such as thiols or phenols.
Although oxidation reactions are critical for life, they can also be damaging; hence, plants and animals maintain complex systems of multiple types of antioxidants, such as glutathione, vitamin C, and vitamin E as well as enzymes such as catalase, superoxide dismutase and various peroxidases. Low levels of antioxidant molecules or inhibition of these antioxidant enzymes can cause oxidative stress, and may damage or kill cells.
Free radical production is actually a normal part of life, part of the equation of simply breathing in oxygen. The process of oxidation in the human body damages cell membranes and other structures including cellular proteins, lipids and DNA. When oxygen is metabolized, it creates ‘free radicals’ which steal electrons from other molecules, causing damage. The body can cope with some free radicals and needs them to function effectively. However, an overload of free radicals has been linked to certain diseases, including heart disease, liver disease and some cancers. Oxidation can be accelerated by stress, cigarette smoking, alcohol, sunlight, pollution and other factors. Antioxidants counteract these cellular by-products and bind with them before they can cause damage.
Harmful free radicals are toxic molecules of oxygen that damage every area of our bodies. A free radical is an unstable, incomplete molecule because it is missing an electron. Free radicals steal an electron from another molecule, thereby creating another free radical. This new free radical then duplicates the process, resulting in a chain reaction of events, which can ultimately damage the body. Free radicals are natural by-products of ongoing biochemical reactions within the body, including ordinary metabolic processes and immune system responses. The common free radicals are: oxygen reactive species (ROS), superoxide radicals, hydroxyl radicals, and peroxyl radicals which can be internally produced by cellular metabolism, inflammation by immune cells and externally by radiation, pharmaceuticals, hydrogen peroxide, toxic chemicals, smoke, alcohol, oxidized polyunsaturated fats and cooked food. Free radicals can cause damage to parts of cells such as proteins, DNA, and cell membranes by stealing their electrons through a process called oxidation. Free radicals may cause heart damage, cancer, cataracts, and a weak immune system.