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  3. For years the media, food labels, dietitians, and even scientists who should

For years the media, food labels, dietitians, and even scientists who should

游客2024-05-22  44
问题     For years the media, food labels, dietitians, and even scientists who should know better have bombarded (轰炸) us with advice to load up on antioxidants: compounds found mostly in fruits and vegetables that mop up free radicals, which are highly reactive clusters of atoms that have been fingered as the evil-doers responsible for aging and for illnesses from cancer to heart disease.
    Not so fast. First, studies piled up showing that taking antioxidants — even such common and seemingly harmless ones as vitamins C and E — as supplements was not beneficial to health and might even be dangerous. Many of the free radicals that are neutralized by antioxidants perform valuable functions in the body. The most important: fighting toxins (毒素) and fighting cancer. Maybe it’s not such an excellent idea to flood the body with something that neutralizes these warriors of the immune system. Or as British chemist and science writer David Bradley noted in his blog, Reactive Reports, "It’s always struck me as odd that you would want to absorb extra antioxidants anyway, given that oxidizing agents are at the front-line of immune defense against pathogens(病原体) and cancer cells... Suffice to say that taking antioxidant supplements... may not necessarily be good for your health if you already have health problems, especially cancer or an infection."
    The first hints that the trend was crashing came from the hundreds of studies that have tried to assess the health effects of antioxidant supplements. The results have not been pretty. In 2008 the Cochrane Collaboration, an international organization of scientists who assess medical research, carefully checked 67 studies with nearly 400,000 participants. The goal: to determine whether antioxidant supplements reduce mortality in either healthy people or in people with diseases. Conclusion: "We found no evidence to support antioxidant supplements for primary or secondary prevention, and Vitamin A and E may increase mortality." In analyses of antioxidant supplements and Lou Gehrig’s disease, Alzheimer’s or mild cognitive impairment, and lung cancer, the Cochrane scientists’ verdict was the same: no. And each analysis had an alarming refrain about increasing overall mortality.
    It’s not clear why antioxidants in supplement form might be so dangerous. One idea holds that at high doses they become pro-oxidants, stimulating the harmful DNA- and cell-damaging reactions they’re supposed to prevent. But a more likely explanation is that we are seeing the human version of what scientists are finding in studies of lab animals: antioxidants interfere with immune-system cells that fight infection and cancer. [br] High doses of antioxidant supplements are assumed dangerous to human body because they can
选项 A、damage DNA pro-oxidants and regular cells
B、oxidize cancer cells and the harmful DNA
C、fight against pathogens in human immune system
D、stimulate harmful reactions to human bodies
答案 D
解析 根据题干中的High doses将本题出处定位到末段第二句。该句提到，有一种观点认为，当抗氧化剂剂量过高时，它们就会变成促氧化剂，刺激它们本来应该预防的有害的DNA和细胞破坏反应。也就是说，大剂量的抗氧化剂刺激对人体的有害反应，[D]与文中的stimulating the harmful．．．reactions对应，故为答案。[A]是综合文中的pro-oxidants和harmful DNA-and cell-damaging设的干扰项。综合第二句以及末句提到的“它们干扰了癌症的免疫系统细胞”可以排除[B]。由第二段第六句可知，[C]是oxidizing agents(氧化剂)的作用，故排除。
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