Dietary supplementation with
B-vitamins that lower plasma total
homocysteine concentrations are expected to lower the risk of
cardiovascular disease.
Folic acid and
vitamin B (12) lower blood
homocysteine concentrations by about 25-30% in populations without
folic acid fortification, but by only 10-15% in populations with fortification. In observational studies, 25% lower
homocysteine is associated with about 10% less
coronary heart disease (CHD) and about 20% less
stroke. This review examines the current status of 12 large-scale randomized trials of
B-vitamin supplementation and risk of
cardiovascular disease. Seven of these trials are being performed in populations without fortification (five involving participants with prior CHD, two with prior
stroke) and five in populations with fortification (two with prior CHD, two with renal disease, and one with prior
stroke). Many of these trials may not have included a sufficient number of people or lasted long enough to have adequate power to exclude false-negative results. Taken together, however, these trials involve 32,000 patients with prior
vascular disease in unfortified populations and 20,000 (14,000 with
vascular disease and 6000 with renal disease) patients in fortified populations. A metaanalysis of these trials should have adequate power to determine whether
homocysteine-lowering
vitamin supplements can reduce the risk of
cardiovascular disease.