Folate status in the US population 20 y after the introduction of folic acid fortification

Abstract

ABSTRACT Background Enriched cereal-grain products have been fortified in the United States for >20 y to improve folate status in women of reproductive age and reduce the risk of folic acid–responsive neural tube birth defects (NTDs). Objectives Our objectives were to assess postfortification changes in folate status in the overall US population and in women aged 12–49 y and to characterize recent folate status by demographic group and use of folic acid–containing supplements. Methods We examined cross-sectional serum and RBC folate data from the NHANES 1999–2016. Results Serum folate geometric means increased from 2007–2010 to 2011–2016 in persons aged ≥1 y (38.7 compared with 40.6 nmol/L) and in women (35.3 compared with 37.0 nmol/L), whereas RBC folate showed no significant change. Younger age groups, men, and Hispanic persons showed increased serum and RBC folate concentrations, whereas non-Hispanic black persons and supplement nonusers showed increased serum folate concentrations. The folate insufficiency prevalence (RBC folate <748 nmol/L; NTD risk) in women decreased from 2007–2010 (23.2%) to 2011–2016 (18.6%) overall and in some subgroups (e.g., women aged 20–39 y, Hispanic and non-Hispanic black women, and supplement nonusers). After covariate adjustment, RBC folate was significantly lower in all age groups (by ∼10–20%) compared with persons aged ≥60 y and in Hispanic (by 8.2%), non-Hispanic Asian (by 12.1%), and non-Hispanic black (by 20.5%) compared with non-Hispanic white women (2011–2016). The 90th percentile for serum (∼70 nmol/L) and RBC (∼1800 nmol/L) folate in supplement nonusers aged ≥60 y was similar to the geometric mean in users (2011–2014). Conclusions Blood folate concentrations in the US population overall and in women have not decreased recently, and folate insufficiency rates are ∼20%. Continued monitoring of all age groups is advisable given the high folate status particularly in older supplement users.