Effect of folic acid on nitrate tolerance in healthy volunteers: differences between arterial and venous circulation.

This study investigated whether oral supplemental folic acid can prevent the development of nitrate tolerance and whether it has different effects on the arterial and venous systems. Twenty-four healthy male volunteers received either placebo or folic acid (10 mg/d) for 14 days. Additionally, all subjects underwent concurrent transdermal nitroglycerin therapy for 7 days. Venous occlusion forearm strain gauge plethysmography measured arterial and venous responses to sublingual nitroglycerin before and after treatment. Both arterial and venous responses were blunted in the placebo group after transdermal nitroglycerin. Folic acid prevented the development of nitrate tolerance in arteries but had no effect in veins.