2. 外语
  3. For years the media, food labels, dietitians, and even scientists who should know better have bombarded (轰炸) us with advice to l

For years the media, food labels, dietitians, and even scientists who should know better have bombarded (轰炸) us with advice to l

admin2013-05-04  47
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.
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 事实细节题。定位句指出，抗氧化物补充剂如此危险的原因尚不明确；有一种观点认为补充过高剂量的抗氧化物补充剂可以使它们自身变成促氧化剂，刺激原本要预防的DNA及细胞破坏反应。因此，D)“刺激对人体有害的反应”，符合题意，故为本题答案。A)“破坏DNA促氧化剂和正常细胞”，原文提到抗氧化剂变成促氧化剂，并没有提到DNA促氧化剂，故排除；B)“氧化癌细胞和有害DNA”，原文未提及，故排除；C)“与人类免疫系统中的病原体抗争”，与原文不符，故排除。
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