Aggressive oxygen species (such as superoxide anion, hydroxyl radical, singlet oxygen and longer-lived reaction products (e.g. hydroperoxides, alkenals) have been implicated in cancerogenesis but it is very difficult to show their direct role in vivo. Indirect evidence can be obtained from the inspection of the body’s multilevel defense system against oxygen radicals which includes essential antioxidants, i.e. β-carotene and the vitamins A, C and E. Since the dietary supply of the latter can vary considerably cancerogenesis might, at least in part, be inversely related to the status of antioxidant vitamins. There is growing evidence in animals and humans in favour of this concept. In animals vitamin A deficiency results in metaplasia whereas experimentally induced tumors can be diminished by β-carotene, vitamins A, C and E. In the human many dietary surveys have convincingly shown that the intake of fresh fruits and leafy green-yellow vegetables as well as the calculated consumption of the above mentioned essential antioxidants is inversely related to the mortality from cancers (1–4). Dietary surveys have, however, inherent weaknesses and thus require confirmation by the measurement of plasma antioxidants in prospective studies.
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- Cancer Mortality Inversely Related to Plasma Levels of Antioxidant Vitamins
K. Fred Gey
Georg B. Brubacher
Hannes B. Stähelin
- Springer US