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复合维生素对于预防慢性疾病几乎没有什么益处，应当避免服用复合维生素

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周一公布了两项新临床试验的结果后，专家说，复合维生素对于预防慢性疾病几乎没有什么益处，应当避免服用复合维生素。

《内 科医学年鉴》(Annals of Internal Medicine)刊登了上述严格进行的研究。研究显示，复合维生素对认知功能或心血管健康没有影响。这也是表明食物补充剂对于普遍营养良好的西方人群几 乎没有什么健康益处的最新报告。此前已有一系列报告得出这样的结论，包括上个月对26项维生素研究的回顾。

四位医师和公共健康专家在伴随研究发布的评论中写道：传递出的信息很简单，那就是大多数食物补充剂无法预防慢性疾病或死亡，并没有服用它们的正当理由，应当避免服用。

评论补充说，在其他一些试验中，β胡萝卜素、维生素E以及还可能包括高剂量的维生素A会增加死亡的风险。

市 场研究机构欧睿信息咨询有限公司(Euromonitor International)的数据显示，全球维生素产业十分庞大，去年销售额达到234亿美元，较2011年提高了3%。具体而言，复合维生素的销售额 去年增长了2.5%，达到142亿美元。疾病控制和预防中心(Centers for Disease Control and Prevention)最新的数据显示，大约40%的美国人报告说他们在2003年至2006年间服用复合维生素或矿物质。

维生素行业组织对上述评论提出批评，并指出去年一项对1.5万名男性的研究表明，每日服用适量复合维生素可以降低患癌风险。一些专家认为上述研究结果不具代表性。

行业组织天然产品协会(Natural Products Association)的执行董事肖(John Shaw)说，这个国家的许多消费者仅靠他们摄入的食物无法获取建议的营养，而复合维生素及矿物质补充剂是一种可以负担得起的替代选择。

新 试验之一评估了维生素如何影响5,947名65岁及以上年龄男性医师的认知功能。参加试验者被分为两组，每天分别给他们辉瑞公司(Pfizer Inc.)生产的复合维生素善存银片(Centrum Silver)或安慰剂。他们的认知功能在试验之初会被评估，之后在12年的时期内再至多评估三次。研究人员发现，试验期内，服用复合维生素和安慰剂的两 组人在平均认知功能的改变方面没有区别。

哈佛大学(Harvard University)和布里格姆妇女医院(Brigham and Women's Hospital)的医学教授Francine Grodstein领导了上述研究。她称研究结果令人失望，但说她并不准备像评论作者推荐的那样放弃维生素。她说，如果进行更长时间的研究，或者对教育程 度不太高、饮食摄入情况不太好的人群进行试验，可能会得出不同的结果。

辉瑞说，善存银片等复合维生素的主要目的在于帮助人们弥补通过饮食摄入的营养不足的情况，而不是为了诊断、治疗、治愈或是预防任何疾病。

第 二个试验有1,708名年龄在50岁及以上的患者参与，这些人全都在至少六周前发作过一次心脏病。他们之中一部份人拿到的是大剂量的复合维生素，另一部份 人拿到的是安慰剂。这份研究表明，服用维生素并不能降低患者死亡或未来发生心血管问题——比如心脏病或突发中风——的风险。

不过领导这项研究的研究人员说，有些患者退出了试验，有些患者没有服用维生素或安慰剂，使得该研究多少打了点折扣。

领 导这次研究的哥伦比亚大学(Columbia University)的心脏病学家拉马斯(Gervasio Lamas)说，他几十年来一直告诫他的病人不要服用维生素。他说，我们治疗的不是营养不良的患者，我从没见过哪个病人患有坏血病或脚气。他提到的这两种 病是因为维生素C和维生素B1缺乏造成的。他说，如果一个健康的人想要保持健康的话，应该做的是停止吸烟、锻炼身体、降低体重，如果有高血压或胆固醇偏高 的话，就按医嘱服药。

拉马斯和其他研究人员指出，特定维生素和矿物质已经被证明对目标人群有益。比如，叶酸就被广泛推荐给孕妇服用，用以预防新生儿在大脑或是脊柱方面的缺陷。评论文章的作者指出，维生素D在防止老年人跌倒方面的可能益处还需要进一步的研究。

公共健康专家们说，研究表明复合维生素对非洲和亚洲的营养不良人群有益处。

在上述最新临床试验之前，同一份医学期刊曾于上月发表了一篇评论文章，该文对26项研究（有关维生素和矿物补充剂对慢性病的作用）进行了分析。研究人员说，他们发现，对没有已知营养缺陷的健康个人而言，没有一致的证据表明，补充剂对心血管疾病、癌症或全因死亡率有影响。

去 年对1.5万人进行的、表明善存银片可轻微降低罹患癌症几率的研究在医生之间引发了分歧。美国约翰·霍普金斯大学(Johns Hopkins University)的药学教授阿佩尔(Lawrence Appel)称这一结果显示出的只是"微乎其微的影响"，并没有改变他对补充剂的整体观点。阿佩尔帮助撰写了这篇反对服用维生素的评论文章。

Multivitamins offer almost no benefit in preventing chronic disease 'and they should be avoided,' experts said Monday in releasing the results of two new clinical trials.

The rigorously conducted studies, published in the Annals of Internal Medicine, showed multivitamins had no effect on cognitive function or cardiovascular health. They are the latest in a series of reports-including a review last month of 26 vitamin studies-indicating that supplements have little health benefits in generally well-nourished, Western populations.

'The message is simple: Most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided,' four physicians and public health experts wrote in an editorial accompanying the studies.

The editorial added that beta-carotene, vitamin E and possibly high doses of vitamin A increased the risk of death in some other trials.

The global vitamin industry is huge, with sales last year of $23.4 billion, up 3% from 2011, according to Euromonitor International. Sales of multivitamins specifically rose 2.5% last year, to $14.2 billion. About 40% of Americans reported taking multivitamins or minerals between 2003 and 2006, the most recent data available, according to the Centers for Disease Control and Prevention.

Vitamin-industry groups criticized the editorial, and pointed to a study last year of 15,000 men, which indicated that daily use of a multivitamin modestly reduced the risk of cancer. Some experts consider the results an outlier.

'It's no secret that many consumers in this country don't get the recommended nutrients from their diet alone, and multivitamin and mineral supplements are an affordable alternative,' said John Shaw, executivedirector of the Natural Products Association, a trade group.

One of the new trials assessed how vitamins affected cognitive function in 5,947 male physicians aged 65 years or older. Participants were given either a daily multivitamin-PfizerInc.'s Centrum Silver-or placebo pills, and their cognitive function was assessed at the outset and again up to three times during a 12-year period. Researchers found no difference in the mean cognitive change over time between the vitamin and placebo groups.

Francine Grodstein, a professor of medicine at Harvard University and Brigham and Women's Hospital in Bostonwho led the study, called the results disappointing, but said she wasn't ready to write off vitamins to the same extent as the editorial writers. Longer studies or trials in less highly educated populations with poorer diets could yield different results, she said.

Pfizer said multivitamins such as Centrum Silver are 'primarily intended to help people fill dietary gaps when they aren't fulfilling their nutritional needs through food alone, and are not intended to diagnose, treat, cure or prevent any disease.'

The second trial involved 1,708 patients aged 50 or older who had suffered a heart attack at least six weeks earlier. They were given either high-dose multivitamins or a placebo. The study showed that taking vitamins didn't reduce a patient's risk of dying or of suffering further cardiovascular problems, such as heart attack or stroke.

Researchers who led that study said it was somewhat undermined by patients withdrawing from the trial or failing to take their vitamins or placebos.

Gervasio Lamas, a Columbia University cardiologist who led the study, said he has been telling his patients 'for decades' not to take vitamins. 'We're not taking care of patients with nutritional deficiency. I've never seen a patient with scurvy or beriberi,' he said, referring to diseases caused by deficiencies in vitamins C and B1. 'If you're a healthy person trying to stay healthy, the money is in stopping smoking, exercising, losing weight' and taking any prescriptions for hypertension or cholesterol, he said.

Dr. Lamas and others noted that certain vitamins and minerals have proved beneficial in targeted populations. Folic acid, for instance, is widely recommended to pregnant women to prevent birth defects of the brain or spine. And the possible benefits of vitamin D in preventing falls among the elderly require further study, according to the authors of the editorial.

Multivitamins also have shown benefit in malnourished populations in Africa and Asia, public health experts said.

The latest clinical trials follow a review published last month in the same medical journal, which examined 26 studies on the effects of vitamin and mineral supplements in chronic disease. The researchers said they found 'no consistent evidence that the included supplements affected [cardiovascular disease], cancer, or all-cause mortality in healthy individuals without known nutritional deficiencies.'

The study last year that showed Centrum Silver produced a modestly lower risk of cancer among 15,000 men left doctors divided. Lawrence Appel, a professor of medicine at Johns Hopkins University who helped write the anti-vitamin editorial, called the result a 'very tiny effect,' one that didn't sway his overall view on supplements.



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