New standard for dietary folate intake in pregnant women.

The Institute of Medicine Panel for Folate and Other B Vitamins and Choline considered data from population-based and metabolic studies to revise the dietary intake standards for pregnancy. The recommended dietary allowance (RDA) for pregnant women is the average daily dietary intake sufficient to meet the requirements of 97-98% of pregnant women. The RDA is derived from the amount estimated to meet the requirement of half of healthy pregnant women, or the estimated average requirement (EAR). Maintenance of red cell folate was selected as the primary indicator of adequacy of folate status during pregnancy. The dietary folate equivalent (DFE) was used to interpret studies in which folate was provided as a combination of food folate and synthetic folic acid because folic acid is more bioavailable than is food folate. Many population-based studies confirmed that approximately 680 nmol (approximately 300 microg) folic acid/d consumed in conjunction with a low-folate diet prevented folate deficiency in pregnant women. Additional studies showed that 227 nmol (100 microg) folic acid/d was inadequate to maintain normal folate status in a significant percentage of the groups assessed. The EAR was derived by adding the DFE of this quantity [454 nmol (200 microg)/d] to the EAR for nonpregnant women [725 nmol (320 microg)/d] to provide an EAR of 1178 nmol (520 microg)/d. The RDA of 1362 nmol (600 microg) DFE/d was derived by multiplying the EAR by 1.2 to account for an estimated 10% CV. Data from the metabolic studies support an RDA of 1362 nmol (600 microg) DFE/d on the basis of the maintenance of normal red cell folate concentrations and agree with the findings from the population studies that 1362 nmol DFE/d is adequate to maintain normal folate status in pregnant women.