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目的:判断膳食补充叶酸及维生素 B_(12)或维生素 B_6降低血同型半胱氨酸(homocysteine)浓度的程度。设计:汇总分析以叶酸为基础的维生素补充治疗影响血同型半胱氨酸浓度的多组随机对照临床试验结果。应用多变量回归分析法判断不同剂量的叶酸及加用维生素 B_(12)或维生素 B_6对同型半胱氨酸浓度的影响。对象:12个试验中总共1114例的个体资料。结果:对于治疗前同型半胱氨酸血浓度较高及叶酸血浓度较低者,补充叶酸能更显著地、成比例地及绝对降低血同型半胱氨酸浓度(P<0.001)。对治疗前同型半胱氨酸血浓度及叶酸血浓度分别标化为12μmol/L 及12 nmol/L(近似于西方人群的平均浓度)后,膳食摄入叶酸可降低25%的血同型半胱氨酸浓度(95%可信区间为23%～28%;P<0.001),且叶酸剂量在每天0.5～5mg 的范围内,其效果相似。加用维生素 B_(12)(平均每日0.5mg)可进一步降低7%(3%～10%)的血同型半胱氨酸。而加用维生素 B_6(平均每日16.5mg)则无显著的附加作用。结论:在典型的西方人群中,每日补充0.5～5mg 叶酸及约0.5mg 维生素 B_(12)可望降低血同型半胱氨酸浓度约1/4至1/3(例如从12μmol/L 降至8～9μmoL/L)。目前有必要在高危人群中进行这种膳食治疗的大规模随机试验,以判断降低同型半胱氨酸血浓度是否可降低血管性疾病的危险性。
Aims: To determine whether dietary folic acid supplementation and vitamin B 12 or vitamin B 6 reduce homocysteine levels. DESIGN: A pooled analysis of the results from randomized controlled clinical trials of folic acid-based vitamin supplements on blood homocysteine concentrations. Multivariable regression analysis was used to determine the effects of different doses of folic acid and the addition of vitamin B 12 or vitamin B 6 on homocysteine concentrations. Subjects: A total of 1114 individuals in 12 trials. RESULTS: Folic acid supplementation significantly, proportionally and absolutely reduced blood homocysteine concentrations (P <0.001) for patients with higher homocysteine concentrations and lower folate concentrations before treatment. Pretreatment plasma homocysteine concentrations and folic acid concentrations were normalized to 12 μmol / L and 12 nmol / L (similar to the average concentration of Western populations), dietary folic acid intake can be reduced by 25% of the blood homocysteine (95% confidence interval 23% -28%; P <0.001), and folic acid doses ranged from 0.5 to 5 mg per day, with similar results. Plus 7% (3% -10%) of blood homocysteine can be further reduced with vitamin B 12 (average 0.5 mg daily). The addition of vitamin B_6 (average daily 16.5mg) no significant additional role. CONCLUSIONS: In a typical Western population, daily supplementation of 0.5-5 mg folic acid and about 0.5 mg vitamin B 12 is expected to reduce blood homocysteine concentrations by about 1/4 to 1/3 (eg, from 12 μmol / L drop To 8 to 9 μmoL / L). There is a need for a large randomized trial of such dietary therapy in high-risk groups to determine whether lowering blood levels of homocysteine reduces the risk of vascular disease.