ABSTRACT
An elevated plasma total homocysteine concentration is a risk factor for cardiovascular disease and neural tube defects. A high daily intake of supplemental folic acid is known to decrease total homocysteine concentrations. We studied the effect of low-dose folic acid administration (250 or 500 microg/day for 4 weeks on plasma total homocysteine concentrations and folate status. We also investigated whether total homocysteine concentrations and blood folate concentrations returned to baseline after an 8-week washout period. In this placebo-controlled study, 144 healthy women aged 18-40 years received 500 microg folic acid per day, 500 microg folic acid every second day (250 microg/day), or a placebo tablet with their habitual diet (mean dietary folate intake 280 microg/day). Administration of 250 and 500 microg folic acid per day for four weeks significantly increased folate concentrations in plasma (p<0.001) and red blood cells (p<0.01). Total homocysteine concentrations decreased significantly (p<0.001) in women (n=50) who took 250 microg folic acid daily [mean (+/- SEM) deviation from baseline -11.4 +/-1.98%] and in women (n=45) who took 500 microg folic acid daily (-21.8 +/- 1.49%). Eight weeks after the end of the intervention period (week 12), plasma total homocysteine concentrations in the folic acid-supplemented groups had not returned to baseline (week 0). In conclusion, doses of folic acid as low as 250 microg daily, on an average, in addition to usual dietary intakes of folate, significantly decreased plasma total homocysteine concentrations in healthy, young women. An 8-week washout period was not sufficient for blood folate and plasma total homocysteine concentrations to return to baseline concentration