Homocysteine, vitamins, and coronary artery disease. Comprehensive review of the literature.

OBJECTIVE To summarize results of clinical trials investigating the role of homocysteine (tHcy) as a risk factor for coronary artery disease (CAD) and the role of vitamin therapy (folic acid and vitamins B6 and B12) in primary and secondary prevention of CAD. QUALITY OF EVIDENCE MEDLINE was searched from January 1976 to January 1999 to locate cross-sectional, retrospective and prospective cohort studies and meta-analyses on CAD using the MeSH words homocysteine, folic acid, vitamins B6 and B12, and coronary artery or heart disease. MAIN MESSAGE Elevated tHcy levels are prevalent; most retrospective and cross-sectional studies show an association with increased risk of CAD. Results from recent prospective studies are less consistent. Folic acid, alone or with vitamins B6 and B12, reduces tHcy concentrations in the blood. Results from ongoing randomized controlled trials could determine the effect of vitamins B6 and B12 and folic acid supplementation on CAD-related morbidity and mortality and could indicate whether routine supplementation with these vitamins should be advocated. Before mass screening for tHcy can be done, the tHcy assay must be standardized. CONCLUSION The role of homocysteine and vitamins B6 and B12 in managing CAD is unclear. Routine screening is not recommended.