Folic acid and vitamin B12 are more effective than vitamin B6 in lowering fasting plasma homocysteine concentration in patients with coronary artery disease
Objective: To investigate whether vitamin B6 supplementation had a beneficial effect on lowering fasting plasma homocysteine concentrations in coronary artery disease (CAD) patients.Design: A single-blind intervention study.Setting: The study was performed at the Taichung Veterans General Hospital, the central part of Taiwan.Subjects: A total of 50 subjects were identified by cardiac catheterization to have at least 70% stenosis of one major coronary artery. In all, 42 patients successfully completed this study.Interventions: Patients were randomly assigned to one of five groups and treated with a daily dose of placebo (n=8), 5 mg vitamin B6 (n=8), 10 mg vitamin B6 (n=8), 50 mg vitamin B6 (n=9), or 5 mg folic acid combined with 0.25 mg vitamin B12 (n=9) for 12 weeks.Main outcome measures: Nutrient intakes were recorded by using 24-h diet recalls when patients returned to the cardiology clinic before the intervention (week 0) and at week 12. Vitamin B6 status was assessed by direct measures (plasma pyridoxal 5′-phosphate) and indirect measures (erythrocyte alanine and aspartate aminotransaminase activity coefficient). Fasting plasma homocysteine, serum folic acid, and vitamin B12 were measured.Results: Fasting plasma homocysteine concentration did not respond to high or low doses of vitamin B6 when compared with a placebo treatment after 12 weeks of supplementation. The mean fasting plasma homocysteine concentration, however, decreased significantly after 12 weeks of folic acid combined with vitamin B12 supplementation (P=0.047). Further, within group, mean fasting plasma homocysteine concentration was nonsignificantly increased by 25.5, 16.2, and 18.3% in placebo, 10 mg/day and 50 mg/day vitamin B6 supplemented groups, respectively; whereas folic acid combined with vitamin B12 supplementation significantly reduced fasting plasma homocysteine concentration by 32% (P<0.001).Conclusions: Our results indicate that vitamin B6 supplementation alone is less effective than folic acid combined with vitamin B12 in lowering plasma homocysteine concentrations in CAD patients.Sponsorship: This study was supported by the National Science Council, Taiwan, Republic of China (NSC-91-2320-B-040-023).