Introduction. Free Radicals in Biological Systems. Free Radicals as Mediators of Tissue Injury. Free Radical Biology of Iron. Dietary Prooxidants. Essential Trace Elements in Antioxidant Processes. Vitamins and Related Dietary Antioxidants. Free Radical Pathology and the Genome. The Role of Free Radicals in Cancer and Aging. Free Radicals and Malnutrition. Conclusions. Index.
Itisonlyrecently thatthe naturaloccurrenceoffree radicalsin biological tissue has become widely accepted, and that the suspi cion with which biologists previously viewed the free radicals of radiationchemistryhas beenplacedin a broaderperspective. Now, oxygen-derived free radicals are considered respectable biochemi cal intermediates, given always the caveat that unwanted tissue damage may arise if these active species are produced in such abundance that they overwhelm the natural antioxidant and free radical defense mechanisms, or if these systems have become hypoeffective. Many factors, including several dietary manipula tions, can lead toelevatedproductionofsuperoxide and may result in free radical overload, whereas a deficiency of those micronutri ents associated with the antioxidant defense mec.hanisms may re sult in substantially diminished antioxidant capacity. By now, antioxidants have become a household word and al most everyone is aware of their imponance in protecting the body against attack by active oxygen species. Indeed, it is a paradox of nature that oxygen, which is so essential to sustain aerobic life, ul timately contributes to its destruction. Not surprisingly, recogni tion ofthis dilemma has generated a spate ofantioxidant strategies intended to reduce the risk of tissue damage by rampant oxygen radicals, some sadly based less on science than on speculation.
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