Low-dose folic acid supplementation decreases plasma homocysteine concentrations: a randomized trial

Background: An elevated plasma total homocysteine concentration is a risk f actor for cardiovascular disease and neural tube defects, A high daily inta ke of supplemental folic acid is known to decrease total homocysteine conce ntrations. Objective: We studied the effect of low-dose folic acid administration (250 or 500 mu g/d) for 4 wk on plasma total homocysteine concentrations and fo late status. We also investigated whether total homocysteine concentrations and blood folate concentrations returned to baseline after an 8-wk washout period. Design: In this placebo-controlled study, 144 healthy women aged 18-40 y re ceived 500 mu g folic acid/d, 500 mu g folic acid every second day (250 mu g/d), or a placebo tablet with their habitual diet (mean dietary folate int ake: 280 mu g/d). Results: Administration of 250 and 500 mu g folic acid/d for 4 wk significa ntly increased folate concentrations in plasma (P < 0.001) and red blood ce lls (P < 0.01). Total homocysteine concentrations decreased significantly ( P < 0.001) in women (n = 50) who took 250 mu g folic acid/d [mean (+/-SEM) deviation from baseline: -11.4 +/- 1.98%] and in women (n = 45) who took 50 0 mu g folic acid/d (-21.8 +/- 1.49%). Eight weeks after the end of the int ervention period (week 12), plasma total homocysteine concentrations in the folic acid-supplemented groups had not returned to baseline (week 0). Conclusions: Doses of folic acid as low as 250 mu g/d. on average, in addit ion to usual dietary intakes of folate significantly decreased plasma total homocysteine concentrations in healthy, young women. An 8-wk washout perio d was not sufficient for blood folate and plasma total homocysteine concent rations to return to baseline concentrations.