Dose-dependent effects of folic acid on blood concentrations of homocysteine: a meta-analysis of the randomized trials
Dose-dependent effects of folic acid on blood concentrations of homocysteine: a meta-analysis of the randomized trials
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DOI：
10.1093/ajcn/82.4.806
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发表时间：
2005-10-01
影响因子：
7.1
通讯作者：
Wald, N
中科院分区：
文献类型：
--
作者：
Clarke, R;Frost, C;Wald, N
背景资料：饮食中补充B族维生素可以降低血中同型半胱氨酸的浓度，这有望降低心血管疾病的风险，但是对于用于此目的的最佳方案还存在不确定性。目的：目的是确定与同型半胱氨酸浓度最大降低相关的叶酸的最低剂量，并确定维生素B-12和B-6的额外相关性。设计：对25项随机对照试验进行荟萃分析，涉及2596名受试者的个体数据，评估了不同剂量叶酸和添加维生素B-12和B-6对血浆同型半胱氨酸浓度的影响。叶酸引起的血浆同型半胱氨酸浓度的降低比例在同型半胱氨酸水平较高时更大（P < 0.001）和较低的叶酸（P < 0.001）的预处理浓度;他们也高于男性女性（P < 0.001）。性别标准化后，治疗前血浆同型半胱氨酸浓度为12 μ mol/L，叶酸浓度为12 nmol/L，每日剂量为0.2、0.4、0.8、2.0和5.0 mg的叶酸可使同型半胱氨酸降低13%，（95%CI：10%，16%）、20%（17%，22%）、23%（21%，26%）、23%（20%，26%）、25%（22%，28%）。维生素B-12（x：0.4 mg/d）使同型半胱氨酸浓度进一步降低7%（95%CI：4%，9%），但维生素B-6无显著作用。结论：每日剂量≥ 0.8 mg叶酸是典型的叶酸补充剂达到血浆同型半胱氨酸浓度最大降低的必要条件。0.2和0.4 mg剂量分别与60%和90%的最大效应相关。
Background: Dietary supplementation with B vitamins that lower blood homocysteine concentrations is expected to reduce cardiovascular disease risk, but there has been uncertainty about the optimum regimen to use for this purpose.Objective: The objectives were to ascertain the lowest dose of folic acid associated with the maximum reductionin homocysteine concentrations and to determine the additional relevance of vitamins B-12 and B-6.Design: A meta-analysis of 25 randomized controlled trials involving individual data on 2596 subjects assessed the effect on plasma homocysteine concentrations of different doses of folic acid and of the addition of vitamins B-12 and B-6.Results: The proportional reductions in plasma homocysteine concentrations produced by folic acid were greater at higher homocysteine (P < 0.001) and lower folate (P < 0.001) pretreatment concentrations; they were also greater in women than in men (P < 0.001). After standardization for sex and to pretreatment plasma concentrations of 12 mu mol homocysteine/L and 12 nmol folate/L, daily doses of 0.2,0.4,0.8,2.0, and 5.0 mg folic acid were associated with reductions in homocysteine of 13% (95% CI: 10%, 16%),20% (17%, 22%), 23% (21%, 26%), 23% (20%, 26%), and 25% (22%, 28%), respectively. Vitamin B-12 (x: 0.4 mg/d) produced 7% (95% CI: 4%, 9%) further reduction in homocysteine concentrations, but vitamin B-6 had no significant effect.Conclusions: Daily doses of >= 0.8 mg folic acid are typically required to achieve the maximal reduction in plasma homocysteine concentrations producedby folic acid supplementation. Doses of 0.2 and 0.4 mg are associated with 60% and 90%, respectively, of this maximal effect.