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   方舟子的“医学科普”真是个奇迹。在《复方甘草片，方舟子及科普》一文中【1】,我们已经领略了方舟子为了“证明”中药有毒，如何舍弃最新而正确的甘草酸数据不用，而宁愿采用旧而错误的数据，以及他如何“曲解”和“断章取义”地引证英文文献为其帖子服务的。

   在方舟子的另一篇关于维C银翘片的帖子中，又故伎重演，再次“曲解”和“断章取义”地引证英文文献为其帖子服务。

   方舟子说：“多项临床对比试验表明服用维生素C对预防或治疗普通感冒没有效果”【2】。方舟子为了证明这句话的力量，在原文中给出了一个英文文献【3】。如果读者能读点英文的话，就会发现，方舟子所给出的文献恰恰得出了和方舟子不一样的结论。这是一篇作者综合他们另一篇关于Vc和感冒关系的多项试验和数据综述【4】的文章。

   原文说：

   Incidence was not altered in the subgroup of 23 community studies where prophylactic doses as high as 2 g daily were used. But a subgroup of six studies of marathon runners, skiers, and soldiers exposed to significant cold and/or physical stress experienced, on average, 50% reduction in common cold incidence.

   很明显，在23个普通社区的试验中，发现Vc对预防和治疗普通感冒没有什么效果。但是，作者后面有个But，里面说对于6组参加象马拉松，滑雪或士兵这些非常容易感冒的人群来说，服用Vc可以降低50%得普通感冒的几率。我们可以设想，对于普通社区人群来说，普通感冒发生机会可能本身就非常低。如果人群处于一个非常容易得感冒或有其他体力消耗的环境的时候，这时服用Vc降低得普通感冒的效果就非常明显了(降低50%)。

   虽然Vc对治疗儿童普通感冒没有什么大作用，但是对于预防儿童感冒，还是有效果的。作者说：

   None of the therapeutic trials carried out so far has examined the effect of vitamin C on children, even though the prophylaxis trials have shown substantially greater effect on episode duration in children.

   预防服用Vc， 可以缩短普通感冒病发时间：

   Duration of cold episodes that occurred during prophylaxis was significantly reduced in both children and adults. For children this represented an average reduction of 14% in symptom days, while in adults the reduction was 8%.

   事实上，作者在2007年10月给美国家庭医生杂志的来信中，针对有人根据他们的综述文章不建议用VC作为治理普通感冒的手段，他们进一步对综述文章做了解释【5】，认为对特定的人群，比如儿童和在极端恶劣环境下的人群，Vc是可以缩短感冒期限以及减轻感冒症状的。

   他们说：

   he Cochrane review was limited to placebo-controlled trials in which at least 0.2 g of vitamin C was used per day.2 Most of these trials examined vitamin C administration as regular supplementation and provided strong evidence that vitamin C shortens the duration of colds and alleviates its symptoms. Children benefited more than adults.2 The data also suggested that high doses of vitamin C are more beneficial than low doses.2-6

   Stratification of the regular supplementation trials in children by vitamin C dosage shows a tendency for dose dependency. Four trials, using 0.20 to 0.75 g of vitamin C per day, found an average reduction of 7 percent in common cold duration (95% confidence interval [CI], -19 to 5). Six trials with 1 g of vitamin C per day found an average reduction of 18 percent (95% CI, -32 to -3), and two trials using 2 g of vitamin C per day found an average reduction of 25 percent (95% CI, -50 to 0.1). Therefore, the 13.6 percent estimate for common cold reduction we calculated in the Cochrane review2, based on all 12 trials with children who received at least 0.2 g of vitamin C per day, may underestimate the effect of high doses.

   作者还是倾向于把Vc辅助其他药物，作为治理普通感冒的手段的。他们认为常年服用Vc是没有必要，但是，在刚感冒时就服用VC还是可以的，他们说：

   Consequently, therapeutic vitamin C supplementation soon after the onset of cold symptoms seems more rational.

   因为有个试验证明，在感冒一开始时就服用Vc的话，对减轻感冒是有好处的，可以缩短感冒期限及减轻感冒症状。

   作者的结论其实是倾向于使用Vc来预防感冒或在感冒一开始就服用Vc来减轻症状或缩短感冒时间的。

   当然，作者最后也说，许多试验结果相互矛盾，主要是因为试验方法不同所致。

   总之，看了那篇文章，我们绝不会得出方舟子的“多项临床对比试验表明服用维生素C对预防或治疗普通感冒没有效果”的结论。

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   【1】复方甘草片，方舟子及科普 http://www.starlakeporch.net/bbs/read.php?1,39666,39666#msg-39666

   【2】 方舟子 常用中成药的真相——维C银翘片

   http://www.xys.org/xys/netters/Fang-Zhouzi/blog/weicyinqiaopian.txt

   【3】 Robert M. Douglas, Harri Hemilä, Vitamin C for Preventing and Treating the Common Cold PLoS Med. 2005, 2(6): e168

   【4】 Douglas RM, Hemilä H, D'Souza R, Chalker EB, Treacy B (2004) Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2004:CD000980.pub2

   http://medicine.plosjournals.org/archive/1549-1676/2/6/supinfo/10.1371_journal.pmed.0020168.sd001.pdf

   [5] Am Fam Physician. 2007 Oct 15;76(8):1111, 1115. HARRI HEMILÄ The Role of Vitamin C in the Treatment of the Common Cold http://www.aafp.org/afp/20071015/letters.html#l2