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滥用维生素营养补充剂提高死亡率

作者：益民

　　国际权威医学刊物《美国医学会杂志》（Journal of American Medical 
Association）在2007年2月28日出版的一期中发表了一篇综合比较-分析论文，
对1990年至2005年10月国际上发表的68项关于维生素营养补充剂与若干疾病死亡
率之间关系的论文进行了系统分析，得出的结论令人吃惊：服用抗氧化类维生素
营养补充剂对降低死亡率没有任何帮助，其中人们常用的维生素A、维生素E和胡
萝卜素等反而会显著提升死亡率：服用维生素A的人死亡率提高4%；服用维生素E
死亡率提高16%；服用胡萝卜素的死亡率提高7%；服用维生素C对死亡率没有影响
（无论好坏）。但该报告没有给出死亡提高的直接原因。

　　富含抗氧化剂的维生素被认为能够延缓某些人体器官组织（如心血管）的老
化、甚至具有一定的抗癌变功能。但国际上亦有研究认为维生素的功能只有以食
物形态（如蔬菜、水果、谷物）被摄取才能被人体有效吸收，而加工成片剂形态
的营养补充剂则难以被人体吸收。但迄今为止鲜有大规模、权威的研究能够确认
长期服用维生素营养补充剂会提高服用者的死亡率。

　　主导此项研究的是设在丹麦哥本哈根大学医院的科克兰肝胆病审核小组
（Cochrane Hepato-Biliary Group）。该小组是国际权威的医学研究循证组织
---科克兰合作机构（Cochrane Collaboration）---下设的专业审核小组之一。
科克兰合作机构是由世界90多个国家的1万多名权威医学专家自愿组成的非营利
机构，下设50多个专业审核小组，在世界90多个国家设有可克兰中心，每年发表
大量专项研究报告，对各种医疗产品和技术的有效性和证据进行独立的论证。

　　该研究将68项（涉及23万多人）相关研究分为“低偏差”和“高偏差”两类。
对两类研究综合（即不分类）比较分析的结果表明，服用维生素与死亡率没有明
显的相关关系，但剔除可靠度较差的“高偏差”类研究，仅对“低偏差”类的47
项研究（涉及18万多人）的分析结果则显示，长期服用维生素会显著增加死亡的
风险。

　　注：以上信息编自美联社、路透社、新闻周刊等刊物的网络版。下面是《美
国医学会杂志》刊登的该研究的摘要。因本人非该刊物订阅者，故没有阅读到研
究报告的全文。

Mortality in Randomized Trials of Antioxidant Supplements 
for Primary and Secondary Prevention

Systematic Review and Meta-analysis

Goran Bjelakovic, MD, DrMedSci; Dimitrinka Nikolova, MA; Lise Lotte 
Gluud, MD, DrMedSci; Rosa G. Simonetti, MD; Christian Gluud, MD, 
DrMedSci 

JAMA. 2007;297:842-857. 

Context  Antioxidant supplements are used for prevention of several 
diseases. 

Objective  To assess the effect of antioxidant supplements on 
mortality in randomized primary and secondary prevention trials. 

Data Sources and Trial Selection  We searched electronic databases and 
bibliographies published by October 2005. All randomized trials 
involving adults comparing beta carotene, vitamin A, vitamin C 
(ascorbic acid), vitamin E, and selenium either singly or combined vs 
placebo or vs no intervention were included in our analysis. 
Randomization, blinding, and follow-up were considered markers of bias 
in the included trials. The effect of antioxidant supplements on 
all-cause mortality was analyzed with random-effects meta-analyses and 
reported as relative risk (RR) with 95% confidence intervals (CIs). 
Meta-regression was used to assess the effect of covariates across the 
trials. 

Data Extraction  We included 68 randomized trials with 232 606 
participants (385 publications). 

Data Synthesis  When all low- and high-bias risk trials of antioxidant 
supplements were pooled together there was no significant effect on 
mortality (RR, 1.02; 95% CI, 0.98-1.06). Multivariate meta-regression 
analyses showed that low-bias risk trials (RR, 1.16; 95% CI, 1.05-1.29) 
and selenium (RR, 0.998; 95% CI, 0.997-0.9995) were significantly 
associated with mortality. In 47 low-bias trials with 180 938 
participants, the antioxidant supplements significantly increased 
mortality (RR, 1.05; 95% CI, 1.02-1.08). In low-bias risk trials, 
after exclusion of selenium trials, beta carotene (RR, 1.07; 95% CI, 
1.02-1.11), vitamin A (RR, 1.16; 95% CI, 1.10-1.24), and vitamin E (RR, 
1.04; 95% CI, 1.01-1.07), singly or combined, significantly increased 
mortality. Vitamin C and selenium had no significant effect on 
mortality. 

Conclusions  Treatment with beta carotene, vitamin A, and vitamin E 
may increase mortality. The potential roles of vitamin C and selenium 
on mortality need further study. 

Author Affiliations: The Cochrane Hepato-Biliary Group, Copenhagen 
Trial Unit, Center for Clinical Intervention Research, Copenhagen 
University Hospital, Rigshospitalet, Copenhagen, Denmark (Drs 
Bjelakovic, L. L. Gluud, Simonetti, and C. Gluud and Ms Nikolova); 
Department of Internal Medicine, Gastroenterology and Hepatology, 
University of Nis, Nis, Serbia (Dr Bjelakovic); and Divisione di 
Medicina, Ospedale V. Cervello, Palermo, Italy (Dr Simonetti). 

Source: http://jama.ama-assn.org/cgi/content/abstract/297/8/842

(XYS20070301)

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