Folic acid reduces risks of having fetus affected with neural tube defects: dietary food folate and plasma folate concentration

OBJECTIVES: Risk of having fetus affected with neural tube defects can be reduced by maternal periconceptional folic acid supplementation. The purpose of the present study is to investigate how folate is taken from diets and to measure plasma folate concentrations. SUBJECTS AND METHODS: A total of 222 women comprising 5 groups, i.e., healthy women, mothers of myelodysplastic patients, pregnant women, myelodysplastic patients, nurse students, participated in our study. Food frequency questionnaires kept 3 days were analyzed based on the 5th standard table of food composition in Japan. Plasma folate concentrations were measured by means of chemiluminescent immunoassay method. Changes in plasma folate concentrations and possible adverse effects following the folic acid supplementation for 16 weeks were also investigated. RESULTS: The dietary intake of folate, plasma folate concentration and energy intake averaged 293 micrograms/day, 8.1 ng/ml and 1,857 Kcal, respectively, among the subjects. Pregnant women took the largest amount of folate from diets and demonstrated the highest plasma folate concentration among the groups. The dietary folate in myelodysplastic patients and nurse students was significantly lower compared to that of healthy women. The Recommended Dietary Allowance of folate was not fulfilled in 22% of non-pregnant adult women and 72% of pregnant women. The dietary folate was mainly taken from the 3rd food group but the 4th group of food was consumed most. Mean folate intake was significantly correlated with circulating concentrations of serum folate (p = 0.012 r = 0.186). The consecutive administration of 400 micrograms supplements for 16 weeks increased a baseline plasma value of 8.7 ng/ml to 32.6 but fell down rapidly to 17.3 24 hours later without any adverse effects. CONCLUSIONS: The dietary folate and serum folate concentrations averaged 293 micrograms/day and 8.1 ng/ml, respectively. The former is the first report based on the 5th standard table of food composition in Japan. Majority of pregnant women took less dietary folate than what recommended by the government. Those who are capable of becoming pregnant are recommended to consume much of the 3rd food group and those who are planning to become pregnant are recommended to take 400 micrograms of folic acid supplements from 4 weeks before to 12 weeks after conception.