The proportion of non-pregnant women aged 15 to 44 years with usual daily folic acid intake of 400 mg or more is estimated from questionnaire and dietary recall data as part of the standard NHANES protocol. The method of calculation of dietary folic acid for this objective involves estimating the daily usual intake of synthetic folic acid from foods reported in two 24-hour dietary recalls using a specialized statistical program, PC-SIDE (Nusser et al., 1996). The U.S. Public Health Service published a recommendation in 1992 that all women capable of becoming pregnant consume 400 mg of folic acid daily through supplements and/or fortified foods to prevent the occurrence of neural tube defects (NTDs) (Centers for Disease Control and Prevention, 1992). The folic acid fortification of enriched cereal grain products became mandatory in 1998 (Food and Drug Administration, 1996). Prior to fortification, folic acid intake was monitored only through intake of dietary supplements containing folic acid (U.S. Department of Health and Human Services, 2000). After fortification, monitoring folic acid intake from foods became an important aspect of monitoring total folic acid intake; however it was not possible to distinguish between naturally occurring food folate and synthetic folic acid using data from NHANES until 2001. Further, it was not until the 2003-2004 NHANES that a second day of dietary recall was added, which allowed for the proper estimation of usual intake of folic acid in the population, accounting for both intra- and inter-individual variation in intake (Nusser et al., 1996; Tinker et al., 2010).