Homocysteine and risk of coronary artery disease: Folate is the important determinant of plasma homocysteine concentration

OBJECTIVES: The purposes of this study were to study the effects of folate and vitamins B6 and B12 on plasma homocysteine concentration and to estimate the risks for coronary artery disease (CAD) according to quartiles of plasma homocysteine concentration. METHODS: The study was designed as a case-reference observational study. Case subjects (CAD group, n = 60) were identified by cardiac catheterization to have at least 70% stenosis of one major coronary artery; otherwise, patients were considered for a reference group (n = 60). Risk factors of cardiovascular disease were recorded, including age, sex, blood lipid profile, hypertension, smoking habits, and drinking habits. Plasma homocysteine, folate, pyridoxal 5'-phosphate, and vitamin B12 were measured. RESULTS: CAD subjects had significantly higher mean plasma homocysteine concentrations than did the reference subjects (13.9 +/- 4.9 versus 9.1 +/- 3.3 micromol/L). There were no significant differences between groups with regard to the three B vitamins; however, mean serum folate concentrations for subjects in the highest two quartiles of plasma homocysteine concentration (10.8-13.8 and >/=13.9 micromol/L) were significantly lower than those for subjects in the lowest two quartiles (