An antioxidant is a chemical that prevents the oxidation of other chemicals. In biological systems, the normal processes of oxidation (plus a minor contribution from ionizing radiation) produce highly reactive free radicals. These can readily react with and damage other molecules: in some cases the body uses this to fight infection. In other cases, the damage may be to the body's own cells. The presence of extremely easily oxidisable compounds in the system can "mop up" free radicals before they damage other essential molecules.
The following vitamins have shown positive antioxidant effects:
Retinol (Vitamin A or beta-carotene) has been discovered to protect dark green, yellow and orange vegetables and fruits from solar radiation damage, and is thought to play a similar role in human body. Carrots, squash, broccoli, sweet potatoes, tomatoes, kale, collards, cantaloupe, peaches and apricots are particularly rich sources of beta-carotene.
Ascorbic acid (Vitamin C) is a water-soluble compound that fulfills this role, among others, in living systems. Important sources include citrus fruits (like oranges, sweet lime, etc.), green peppers, broccoli, green leafy vegetables, strawberries, raw cabbage and tomatoes.
Vitamin E (tocopherol) is fat soluble and protects lipids. Sources include wheat germ, nuts, seeds, whole grains, green leafy vegetables, vegetable oil and fish-liver oil.
Selenium is best obtained through foods, as large doses of the supplement form can be toxic. Good food sources include fish, shellfish, red meat, grains, eggs, chicken and garlic. Vegetables can also be a good source if grown in selenium-rich soils.
Several food additives (including ascorbic acid and tocopherol-derived compounds) are used as antioxidants to help guard against deterioration of food.
Other antioxidants are enzymes. These include glutathione peroxidase, superoxide dismutase and catalase.
Much damage is done by free radicals in mitochondria as a byproduct of oxidative phosphorylation. Superoxide radicals are generated which can damage mitochodrial DNA and mitochondrial membranes. Unlike DNA in the cell nucleus, mitochondrial DNA has only a few DNA-repair enzymes and the DNA is not protected by histones.
Many antioxidants, however (including vitamic C and vitamin E) can't get into mitochondria for various reasons (e.g. because too hydrophilic to cross mitochondrial membranes or too hydrophobic to cross the cytoplasm). But a group of scientists in Russia (led by V. Skulachev) has created a custom antioxidant ("Skulachev ion" is forming the point of the molecule and penetrates the mitochondrial membrane and the "antioxidising" part is attached behind it) that can enter the mitochondria and stays there preventing damage to DNA.
The benefits of antioxidants were examined during the Age-Related Eye Disease Study.
The Age-Related Eye Disease Study was a clinical trial sponsored by the National Eye Institute, one of the National Institutes of Health in the United States. The study was designed to:
investigate the natural history and risk factors of age-related macular degeneration (AMD) and cataracts, and
evaluate the effects of high doses of antioxidants and zinc on the progression of the two conditions in those with AMD
The study of 3600 individuals for an average of 6.3 years concluded that high levels of antioxidants and zinc can reduce some people's risk of developing advanced AMD by about 25 percent. Those that benefited from the dietary supplements included those with intermediate-stage AMD and those with advanced AMD in one eye only. The supplements had no significant effect on the development or progression of cataracts. "High levels" in this case were defined to be:
500 milligrams of vitamin C;
400 international units of vitamin E;
15 milligrams of beta-carotene (or 25,000 international units of vitamin A);
80 milligrams of the dietary mineral zinc, in the form of zinc oxide; and
two milligrams of copper as cupric oxide, added to prevent copper deficiency anemia, a condition associated with high levels of zinc intake.
The results were reported in the October 2001 issue of Archives of Ophthalmology.
Antioxidants act as cell protectors.
Oxygen, an essential element for life, can create damaging by-products during normal cellular metabolism. Antioxidants counteract these cellular by-products, called free radicals, and bind with them before they can cause damage. If left unchecked, free radicals may cause heart damage, cancer, cataracts, and a weak immune system.
Antioxidants work by: binding to the free radicals; transforming them into non-damaging compounds; or repairing cellular damage. Antioxidants come in a variety of forms and include Vitamin C, Vitamin E, the Carotenoids, and Selenium.
Good sources of antioxidants include fruits and vegetables. The highest concentrations are found in the most deeply or brightly colored fruits and vegetables (spinach, carrots, red bell peppers, tomatoes).
Antioxidants may help lung function
Studies have shown that diets rich in antioxidants are linked to improved lung function and may prevent respiratory diseases like asthma, emphysema and chronic bronchitis.
A study prepared by the Cornell University in 1998 also suggested that the effects of antioxidants on a person's lungs differ according to whether or not they smoke.
In findings presented to a meeting of the Federation of American Societies for Experimental Biology, the researchers said there are significant benefits associated with consuming high levels of antioxidants like beta carotene and selenium -- substances that protect cells from biochemical damage.
Patricia Cassano, an epidemiologist in Cornell's Division of Nutritional Sciences, said the positive aspects of consuming foods containing antioxidants were comparable to the difference in lung function between a nonsmoker and a long-term smoker.
Have you heard about the benefits of Green Tea as an antioxidant and cancer preventative? Learn about the benefits of this natural ingedient by clicking here.
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