Antioxidants

Antioxidants

Antioxidants are chemical compounds that combat oxidants or oxidizing agents. In the chemical reaction known as oxidation, one reactant loses an electron while the other gains an electron. The reactant that loses an electron is called an oxidant, or free radical." Oxygen in unstable form is the most common free radical in living cells, where hydrogen peroxide has an exposed oxygen atom with a missing electron in its outer orbital. In addition, oxygen can separate from hydrogen peroxide and form an unbonded single oxygen that is extremely reactive. Contaminants in the environment, as well as the normal metabolism of a cell, can change a cellular molecule into a free radical. In that case, the molecule loses an electron in its outer shell, and becomes an unstable reactor in the cell. The free radical aggressively steals an electron from a stable molecule nearby, and the new molecule then becomes a free radical. During this destructive chain of events, free radicals donate their extra electrons to vital cell molecules, such as DNA, proteins, enzymes, and the lipids found in plasma membranes. Free radicals damage the cell at their site of operation, and may cause serious disorders including cancer. Plaque may begin to accumulate in arteries when oxidized low-density lipoprotein (LDL) cholesterol operates as a free radical and damages the artery lining. Plaque impedes circulation in blood vessels, and can lead to heart attack and stroke. Free radicals may also bring about premature aging. Antioxidants, including certain vitamins, detoxify free radicals.

Vitamins were originally recognized as nutritional substances that the body needs to prevent deficiency diseases, such as scurvy.

They were then identified as building blocks of coenzymes, molecules that take part in the catalytic function of enzymes. Recently, scientists also established their role as antioxidants. Vitamins A, E, and C, and the trace element, selenium, form a part of enzymes that destroys free radicals. Antioxidants in foods originate in plants that synthesize them to detoxify oxidants created by the sun's radiation. These substances are plentiful in fruits and vegetables. Nutritionists recommend five servings of fruits and vegetable each day. Some people obtain antioxidants in dietary supplements. Scientists warn against overdosing on vitamins and substituting pills for food.

Researchers are experimenting to determine the role of antioxidants in preventing disease. Some have found that vitamins A, C, and E reduce the chance of contracting rheumatoid arthritis, others discovered that vitamin E helps prevent coronary disease and colorectal cancer. Researchers Gary D. Plotnick, Mary C. Coretti, and Robert A. Vogel described their study on the effect of antioxidants on endothelium (the lining tissue of blood vessels including arteries) in which they divided the participants into two groups: one group was pretreated with antioxidant vitamins C and E while the other was not. The scientists gave all the participants a high-fat meal and then determined their endothelial function. The study showed that the subjects without antioxidants experienced reduced endothelial function for four hours, and those who had the antioxidants avoided the decrease in function.