濫用維生素營養(yǎng)補(bǔ)充劑提高死亡率

作者：益民

　　國際權(quán)威醫(yī)學(xué)刊物《美國醫(yī)學(xué)會雜志》（Journal of American Medical
Association）在2007年2月28日出版的一期中發(fā)表了一篇綜合比較-分析論文，
對1990年至2005年10月國際上發(fā)表的68項(xiàng)關(guān)于維生素營養(yǎng)補(bǔ)充劑與若干疾病死亡
率之間關(guān)系的論文進(jìn)行了系統(tǒng)分析，得出的結(jié)論令人吃驚：服用抗氧化類維生素
營養(yǎng)補(bǔ)充劑對降低死亡率沒有任何幫助，其中人們常用的維生素A、維生素E和胡
蘿卜素等反而會顯著提升死亡率：服用維生素A的人死亡率提高4%；服用維生素E
死亡率提高16%；服用胡蘿卜素的死亡率提高7%；服用維生素C對死亡率沒有影響
（無論好壞）。但該報(bào)告沒有給出死亡提高的直接原因。

　　富含抗氧化劑的維生素被認(rèn)為能夠延緩某些人體器官組織（如心血管）的老
化、甚至具有一定的抗癌變功能。但國際上亦有研究認(rèn)為維生素的功能只有以食
物形態(tài)（如蔬菜、水果、谷物）被攝取才能被人體有效吸收，而加工成片劑形態(tài)
的營養(yǎng)補(bǔ)充劑則難以被人體吸收。但迄今為止鮮有大規(guī)模、權(quán)威的研究能夠確認(rèn)
長期服用維生素營養(yǎng)補(bǔ)充劑會提高服用者的死亡率。

　　主導(dǎo)此項(xiàng)研究的是設(shè)在丹麥哥本哈根大學(xué)醫(yī)院的科克蘭肝膽病審核小組
（Cochrane Hepato-Biliary Group）。該小組是國際權(quán)威的醫(yī)學(xué)研究循證組織
---科克蘭合作機(jī)構(gòu)（Cochrane Collaboration）---下設(shè)的專業(yè)審核小組之一。
科克蘭合作機(jī)構(gòu)是由世界90多個(gè)國家的1萬多名權(quán)威醫(yī)學(xué)專家自愿組成的非營利
機(jī)構(gòu)，下設(shè)50多個(gè)專業(yè)審核小組，在世界90多個(gè)國家設(shè)有可克蘭中心，每年發(fā)表
大量專項(xiàng)研究報(bào)告，對各種醫(yī)療產(chǎn)品和技術(shù)的有效性和證據(jù)進(jìn)行獨(dú)立的論證。

　　該研究將68項(xiàng)（涉及23萬多人）相關(guān)研究分為“低偏差”和“高偏差”兩類。
對兩類研究綜合（即不分類）比較分析的結(jié)果表明，服用維生素與死亡率沒有明
顯的相關(guān)關(guān)系，但剔除可靠度較差的“高偏差”類研究，僅對“低偏差”類的47
項(xiàng)研究（涉及18萬多人）的分析結(jié)果則顯示，長期服用維生素會顯著增加死亡的
風(fēng)險(xiǎn)。

　　注：以上信息編自美聯(lián)社、路透社、新聞周刊等刊物的網(wǎng)絡(luò)版。下面是《美
國醫(yī)學(xué)會雜志》刊登的該研究的摘要。因本人非該刊物訂閱者，故沒有閱讀到研
究報(bào)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./cgi/content/abstract/297/8/842