ABSTRACT
BACKGROUND: The lowest risk of having a child with a neural tube defect (NTD) was related to red blood cell (RBC) folate concentrations of >906 nmol/L. For NTD prevention, it is recommended that women use periconceptional supplementation of 400 microg/day folic acid. Using this dose previous studies indicate that RBC folate >906 nmol/L was not reached within four weeks of supplementation. OBJECTIVE: The effectiveness of a multivitamin/multimineral supplement containing 800 microg folic acid (verum) was evaluated using RBC folate concentration exceeding 906 nmol/L as primary endpoint. In addition, the time frame of achieving the threshold level was established as well as the effect of supplementation of other B vitamins on folate metabolism. SUBJECTS AND METHODS: 46 healthy females received 800 microg/day of folic acid or placebo for 16 weeks. Blood samples were collected in four-week intervals. Plasma and RBC folate were measured with the microbiological method. RESULTS: Mean (+/-SED) RBC folate increased over time to 1430+/-53 nmol/L, but did not reach a steady state after 16 weeks of intervention. Mean time to reach the target level was 4.2 +/- 3.5 weeks in the verum group. Intake of verum also led to an increase over time of plasma folate. CONCLUSIONS: Preventive RBC folate concentration of more than 906 nmol/L can be reached within four weeks of supplementation with daily intake of 800 microg folic acid. With respect to NTD prevention, we suggest the re-evaluation of the current recommendation of folic acid supplementation.
