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The following vitamins have shown positive antioxidant effects:
It should also be noted that many dark berries, including pomegranate, noni, blueberries and blackberries have high concentrations of antioxidants, as do some types of tea, especially Green tea. The highest ORAC value measured in any fruit is in the Mangosteen, particularly in the pericarp, or rind. The FDA has recently suggested that Americans increase their natural antioxidant intake to 7000 ORAC units daily, which is nearly 12 servings of high ORAC value fruit, to help curb the Cancer epidemic. In the absence of consumption of large amounts of antioxidant fruits, nutritional supplements can be used.(Editor's Note: I don't know how you could get this much ORAC value from eating fruit; you would almost certainly have to use nutritional supplementation.)
Several food additives including pectin, Ascorbic acid (Vitamin C) 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 living cell 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 vitamin 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). A group of scientists in Russia (led by V. Skulachev) have created a custom antioxidant (a Skulachev ion forms the point of the molecule and penetrates the mitochondrial membrane; the antioxidising part is attached behind it) that can enter the mitochondria and stays there due to the Membrane potential gradient; preventing damage to DNA.
Tests dating back to the 1950's have indicated that nutritional supplementation of trace amounts of the mineral Selenium is highly beneficial in reducing the actual occurrence, as well as prevention of male Prostate cancer. Recent studies conducted using modern statistical methods by the China national health system have verified these earlier studies.
Although there is little doubt that antioxidants are a necessary component for good health, there is considerable doubt as to the most beneficial antioxidant and as to the optimal amount for results. A study of lung cancer patients found that those given antioxidant supplements had worse prognoses. This is believed to be due to antioxidant interference with the body's normal use of localised free radicals e.g. Nitric oxide for cell signalling. Due to the complex nature of the interactions of antioxidants with the body, it is difficult to interpret the results of many experiments designed to test such things. In vitro testing (outside the body) has shown many natural antioxidants, in specific concentration, can halt the growth of or even kill cancerous cells.
For example, recent studies are suggesting that at high levels, synthetic antioxidant vitamins such as A, E and C may prove to have pro-oxidant effects: increasing the formation of free radicals. The fact that natural antioxidants are always ingested together with a wide variety of flavonoids and other phytochemicals also likely plays a part. Many supplement manufacturers supply more expensive tablets containing these. Newer liquid nutritional supplements using plant ionic compounds are believed to be more readily absorbed in the human body.
The benefits of antioxidants were examined during the Age-Related Eye Disease Study.
The Green tea industry, with makers like Japanese Green Tea and Arizona (for iced) have benefitted tremendously from recent articles on antioxidants in green tea delaying onset of AMD.