(转) The Truth of Vitamins - 维生素真解

矮子

　　The Truth of Vitamins
　　Britain is in the middle of a health revolution. And every day, millions of people take vitamin 1)supplements, convinced of their power to keep them healthy. But there is a growing 2)anxiety from scientists that our habit of taking large 3)doses of some vitamins could have very different 4)consequences.
　　Vitamins are nothing more than 5)chemicals that occur naturally in food. Our bodies cannot produce them themselves, and nearly a century ago scientists discovered just how vital they were for our health. Vitamin A, found in 6)dairy products, liver and fish prevents blindness and growth 7)deformities. Vitamin C, from oranges and other 8)citrus fruit, has all but ended 9)scurvy. And Vitamin D, found in fish, means children need no longer grow up with 10)rickets.
　　But 40 years ago, someone came along who would transform the world’s 11)perception of vitamins. 12)Pauling became convinced that vitamins could not only prevent 13)deficiency diseases, they could do something far, far bigger. The key, according to Pauling, was to take them in huge doses, because that could prevent you from catching the most 14)irritating of diseases, the 15)common cold. But does Vitamin C really prevent the common cold as Linus Pauling believed?
　　Professor Balz Frei is one of the world’s leading experts on Vitamin C. He has studied the evidence from 16)clinical trials involving thousands of volunteers from across the world, designed to 17)investigate Pauling’s claim that large doses of Vitamin C fights the common cold.
　　Professor Frei: I’ve looked at the evidence that Vitamin C can prevent the common cold, but for the general population there is really no evidence from scientific studies that Vitamin C can lower the 18)incidence of the common cold, or prevent it 19)in the first place. So taking Vitamin C supplements is not gonna help prevent the common cold.
　　20)In other words, the director of the very 21)institute set up to pursue Linus Pauling’s work, now believes that the great man was wrong.
　　But there is another anti-22)oxidant vitamin which is popular and about which scientists are much more 23)cautious—Vitamin A.
　　In vegetables, there is a chemical called 24)beta carotene which your body converts into Vitamin A. Studies have shown that people who eat a diet rich in beta carotene are much less likely to develop lung cancer. And this seemed to offer a 25)genuine breakthrough.
　　Demetrius Albanes is one of the leading cancer experts in America. He and his colleagues organised a study to confirm that high dose pills really could save millions of lives.
　　To have the best chance of seeing whether the pills really could prevent lung cancer, they were given to people most likely to develop it— smokers. It seemed that beta carotene pills, which everyone had hoped would prevent lung cancer, were having the exact opposite effect.
　　It was a 26)devastating result. The people taking the pill had shown an 18% increase in lung cancer.
　　Scientists still do not fully understand why beta carotene appears so beneficial in food, but seemed to have such a devastating effect on smokers when taken in a high dose pill. But because of these studies, in 2003, safety experts in the U.K. advised smokers not to take beta carotene supplements. And advised everyone to limit their daily 27)intake from high dose pills. These studies were a 28)salutary lesson that vitamin supplements were not just some harmless natural 29)remedy. In high doses they could have unexpected and dangerous consequences.
　　Until we understand more about these powerful chemicals, most doctors would advise everybody to seek advice before joining the high dose Vitamin Revolution.

　　维生素真解
　　维生素，一直以来都被人们称为健康要素。到了现代，补充维生素更成为一种潮流，而维生素的健康革命已是众多人士热衷的时尚，然而维生素真的是维持生命健康的灵丹妙药吗？
　　英国正处于一个健康革命之中。每天，数以百万计的人因相信维生素能让他们保持健康而服用维生素补充品。然而科学家们越来越担心，我们大量地服用某些维生素这种习惯可能会弄巧反拙。
　　维生素只不过是在食物中天然存在的化学品。我们的身体不能制造这些化学品。近一个世纪前，科学家们才发现维生素对人类的健康实在至关重要。奶制品、肝脏以及鱼类中含维生素A，它能预防眼睛失明和生长畸形。橙和其它柑橘类水果中含有维生素C，可以防止坏血病。另外，在鱼类中的维生素D可让孩子成长过程中再不会得佝偻病。
　　然而40年前，一个人的理论改变了全世界对于维生素的认识。鲍林深信维生素不仅能够防止营养不良，还能够产生某些远远大于此的效用。根据鲍林的观点，关键在于要大剂量地服用维生素，因为这样能预防你患上最恼人的感冒。但维生素C真的像莱纳斯·鲍林所认为的那样能够预防感冒吗？
　　鲍尔兹·费尔教授是世界上研究维生素C最杰出的专家之一。他研究了过往的临床试验得出的证据。这些临床试验是为研究鲍林关于大剂量的维生素C可防止感冒的说法而设计的，受测者是来自全世界的数千名志愿者。
　　费尔教授：我已经看了维生素C能预防感冒的证据，但是对于普罗大众，科学研究中真的没有证据可以表明维生素C能够降低感冒的发病率或者在发病初期进行预防。因此服用维生素C补充品对于预防感冒没有帮助。
　　换句话说，这个为了继续莱纳斯·鲍林的工作而建立的机构，其负责人现在认为这位大师错了。
　　然而还有另一种属于抗氧化剂的维生素广为人所热衷服用，而科学家们对其态度也更为谨慎，那就是维生素A。
　　在蔬菜中含有一种称为β-胡萝卜素的化学物质，人体会将其转化成维生素A。研究表明饮食中富含胡萝卜素的人得肺癌的机率会小很多。这看起来是一个确实的医学突破。
　　德米特里厄斯·奥尔伯纳斯是美国最杰出的癌症专家之一。他和他的同事组建了一项研究来证实大剂量的β-胡萝卜素片剂真的能够拯救数百万人的性命。
　　为了突显这些β-胡萝卜素片是否真的具有防止肺癌的功效，他们让最有可能患上肺癌的人群——吸烟者——服用β-胡萝卜素。这些每个人都希望能够防止肺癌的β-胡萝卜素片却恰恰起了反作用。
　　那是一个骇人的结果。服用了片剂的人中患肺癌人数增加了18%。
　　科学家们仍然无法完全理解为何β-胡萝卜素在食物中如此有益，但对于服用大剂量片剂的吸烟者却有如此骇人的影响。因为这些研究，在2003年，英国的安全专家建议吸烟者不要服用β-胡萝卜素补充品，并且建议每个人要限制每日片剂的大量摄入。这些研究是一个有益的教训，它告诉人们维生素补充品不只是无害的天然治病之物，服用剂量过多可能导致意想不到的危险后果。
　　在我们对这些有奇效的化学品有更多的了解之前，大多数医生建议每个人在加入大剂量“维生素革命”前要先咨询专家的意见。

tartoo

最新研究表明，维生素对预防感冒没有作用；但对已经感冒的人，是否存在加快患愈，还没有确切的研究。