(轉) The Truth of Vitamins - 維生素真解

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　　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.

　　維生素真解
　　維生素，一直以來都被人們稱為健康要素。到了現代，補充維生素更成為一種潮流，而維生素的健康革命已是眾多人士熱衷的時尚，然而維生素真的是維持生命健康的靈丹妙藥嗎？
　　英國正處于一個健康革命之中。每天，數以百萬計的人因相信維生素能讓他們保持健康而服用維生素補充品。然而科學家們越來越擔心，我們大量地服用某些維生素這種習慣可能會弄巧反拙。
　　維生素只不過是在食物中天然存在的化學品。我們的身體不能制造這些化學品。近一個世紀前，科學家們才發現維生素對人類的健康實在至關重要。奶制品、肝臟以及魚類中含維生素A，它能預防眼睛失明和生長畸形。橙和其它柑橘類水果中含有維生素C，可以防止壞血病。另外，在魚類中的維生素D可讓孩子成長過程中再不會得佝僂病。
　　然而40年前，一個人的理論改變了全世界對于維生素的認識。鮑林深信維生素不僅能夠防止營養不良，還能夠產生某些遠遠大于此的效用。根據鮑林的觀點，關鍵在于要大劑量地服用維生素，因為這樣能預防你患上最惱人的感冒。但維生素C真的像萊納斯·鮑林所認為的那樣能夠預防感冒嗎？
　　鮑爾茲·費爾教授是世界上研究維生素C最杰出的專家之一。他研究了過往的臨床試驗得出的證據。這些臨床試驗是為研究鮑林關于大劑量的維生素C可防止感冒的說法而設計的，受測者是來自全世界的數千名志愿者。
　　費爾教授：我已經看了維生素C能預防感冒的證據，但是對于普羅大眾，科學研究中真的沒有證據可以表明維生素C能夠降低感冒的發病率或者在發病初期進行預防。因此服用維生素C補充品對于預防感冒沒有幫助。
　　換句話說，這個為了繼續萊納斯·鮑林的工作而建立的機構，其負責人現在認為這位大師錯了。
　　然而還有另一種屬于抗氧化劑的維生素廣為人所熱衷服用，而科學家們對其態度也更為謹慎，那就是維生素A。
　　在蔬菜中含有一種稱為β-胡蘿卜素的化學物質，人體會將其轉化成維生素A。研究表明飲食中富含胡蘿卜素的人得肺癌的機率會小很多。這看起來是一個確實的醫學突破。
　　德米特里厄斯·奧爾伯納斯是美國最杰出的癌癥專家之一。他和他的同事組建了一項研究來證實大劑量的β-胡蘿卜素片劑真的能夠拯救數百萬人的性命。
　　為了突顯這些β-胡蘿卜素片是否真的具有防止肺癌的功效，他們讓最有可能患上肺癌的人群——吸煙者——服用β-胡蘿卜素。這些每個人都希望能夠防止肺癌的β-胡蘿卜素片卻恰恰起了反作用。
　　那是一個駭人的結果。服用了片劑的人中患肺癌人數增加了18%。
　　科學家們仍然無法完全理解為何β-胡蘿卜素在食物中如此有益，但對于服用大劑量片劑的吸煙者卻有如此駭人的影響。因為這些研究，在2003年，英國的安全專家建議吸煙者不要服用β-胡蘿卜素補充品，并且建議每個人要限制每日片劑的大量攝入。這些研究是一個有益的教訓，它告訴人們維生素補充品不只是無害的天然治病之物，服用劑量過多可能導致意想不到的危險后果。
　　在我們對這些有奇效的化學品有更多的了解之前，大多數醫生建議每個人在加入大劑量“維生素革命”前要先咨詢專家的意見。

tartoo

最新研究表明，維生素對預防感冒沒有作用；但對已經感冒的人，是否存在加快患愈，還沒有確切的研究。