In 1969, McCully reported an association between homocystinuria, a rare metabolic disorder characterized by high blood levels ( 100 mol/L) of the amino acid homocysteine (Hcy), and severe atherosclerosis among postmortem subjects.1 His report is widely recognized as the basis for the “homocysteine hypothesis,” namely, that elevated blood Hcy is a risk factor for cardiovascular disease (CVD). Si...