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. 2019 Aug 27;110(5):1088–1097. doi: 10.1093/ajcn/nqz184

FIGURE 1.

FIGURE 1

Pre- and postfortification median and 90th percentile concentrations of serum (A) and RBC (B) folate in persons aged ≥3 y by survey period, NHANES 1988–2016. Folic acid fortification became mandatory in 1998. Lines between 1988–1994 and 1999–2000 are dashed to indicate that there were several years between these 2 surveys. Error bars represent 95% CIs. For NHANES 1988–1994, biological samples were collected from persons aged ≥4 y only. The 1988–1994 and 1999–2006 radioassay data were adjusted (13) to make them comparable to the 2007–2016 RBC microbiologic assay, 2007–2010 serum microbiologic assay, and 2011–2016 serum LC-MS/MS data. For sample sizes (n), see Supplemental Table 2 for 1999–2016; sample sizes for 1988–1994 were 22,939 (serum folate) and 22,438 (RBC folate).