對那些發(fā)生過一次心肌梗塞的患者來說,，如果用葉酸和維生素B12補充劑來降低他們的同型半胱氨酸的血濃度并不會出現(xiàn)相關(guān)的心肌梗塞、冠心病死亡或中風風險的降低,。 然而，研究人員也發(fā)現(xiàn)，葉酸補充劑沒有像人們所猜測的會增加罹患癌癥的風險,。
根據(jù)文章的背景資料,，同型半胱氨酸的血濃度與心血管疾病具有正相關(guān)性，但人們不確定的是,，這一相關(guān)性是否具有因果關(guān)系,。 文章的作者寫道：“每日服用葉酸補充劑通常可將同型半胱氨酸血濃度降低約25%,，而增添維生素B12還會進一步地降低7個百分點的同型半胱氨酸血濃度。”
University of Oxford, United Kingdom的Jane M. Armitage, F.R.C.P.及其在Study of the Effectiveness of Additional Reductions In Cholesterol and Homocysteine (SEARCH)試驗中的同僚評估了在1萬2064名心肌梗塞幸存者中用葉酸加上維生素B12來降低血液同型半胱氨酸濃度的效果,。該研究是在1998-2008年期間在英國的二級醫(yī)院中開展的,。 這些患者被隨機分配接受或是每日2毫克的葉酸加上1毫克的維生素B12或是接受與之匹配的安慰劑,。
文章的作者得出結(jié)論：“將本次的研究結(jié)果與從前的降低同型半胱氨酸濃度的試驗進行綜合,，SEARCH的結(jié)果表明,，葉酸補充劑即使對心血管疾病沒有產(chǎn)生什么裨益性功效,，但它對癌癥或其它重大的健康問題也沒有顯著的不良反應,。另外，這些結(jié)果凸顯了在預防心血管疾病時應該將重點放在藥物（如：阿斯匹林,、他汀類藥物和降壓藥治療）治療和被證明有好處的生活方式的變更（尤其是戒煙和避免體重過度增加）上的重要性,，而不是用基于葉酸的維生素補充療法來降低同型半胱氨酸,。”（生物谷Bioon.net）
生物谷推薦原文出處：
JAMA. 2010;303(24):2486-2494.
Effects of Homocysteine-Lowering With Folic Acid Plus Vitamin B12 vs Placebo on Mortality and Major Morbidity in Myocardial Infarction Survivors
Jane M. Armitage, FRCP; Louise Bowman, MRCP; Robert J. Clarke, FRCP; Karl Wallendszus, BA, MSc; Richard Bulbulia, FRCS; Kazem Rahimi, MRCP; Richard Haynes, MRCP; and Sarah Parish, PhD, Clinical Trial Service Unit, University of Oxford, Oxford, United Kingdom; Peter Sleight, FRCP, Department of Cardiovascular Medicine, University of Oxford; and Richard Peto, FRS,and Rory Collins, FRCP, Clinical Trial Service Unit, University of Oxford.
Context Blood homocysteine levels are positively associated with cardiovascular disease, but it is uncertain whether the association is causal.
Objective To assess the effects of reducing homocysteine levels with folic acid and vitamin B12 on vascular and nonvascular outcomes.
Design, Setting, and Patients Double-blind randomized controlled trial of 12 064 survivors of myocardial infarction in secondary care hospitals in the United Kingdom between 1998 and 2008.
Interventions 2 mg folic acid plus 1 mg vitamin B12 daily vs matching placebo.
Main Outcome Measures First major vascular event, defined as major coronary event (coronary death, myocardial infarction, or coronary revascularization), fatal or nonfatal stroke, or noncoronary revascularization.
Results Allocation to the study vitamins reduced homocysteine by a mean of 3.8 μmol/L (28%). During 6.7 years of follow-up, major vascular events occurred in 1537 of 6033 participants (25.5%) allocated folic acid plus vitamin B12 vs 1493 of 6031 participants (24.8%) allocated placebo (risk ratio [RR], 1.04; 95% confidence interval [CI], 0.97-1.12; P = .28). There were no apparent effects on major coronary events (vitamins, 1229 [20.4%], vs placebo, 1185 [19.6%]; RR, 1.05; 95% CI, 0.97-1.13), stroke (vitamins, 269 [4.5%], vs placebo, 265 [4.4%]; RR, 1.02; 95% CI, 0.86-1.21), or noncoronary revascularizations (vitamins, 178 [3.0%], vs placebo, 152 [2.5%]; RR, 1.18; 95% CI, 0.95-1.46). Nor were there significant differences in the numbers of deaths attributed to vascular causes (vitamins, 578 [9.6%], vs placebo, 559 [9.3%]) or nonvascular causes (vitamins, 405 [6.7%], vs placebo, 392 [6.5%]) or in the incidence of any cancer (vitamins, 678 [11.2%], vs placebo, 639 [10.6%]).
Conclusion Substantial long-term reductions in blood homocysteine levels with folic acid and vitamin B12 supplementation did not have beneficial effects on vascular outcomes but were also not associated with adverse effects on cancer incidence.
