Unmetabolized Folic Acid Is Detected in Nearly All Serum Samples from US Children, Adolescents, and Adults. Issue 3 (10th December 2014)

• Record Type: Journal Article
• Authors: Pfeiffer, Christine M; Sternberg, Maya R; Fazili, Zia; Yetley, Elizabeth A; Lacher, David A; Bailey, Regan L; Johnson, Clifford L
• Is Part Of: Journal of nutrition. Volume 145:Issue 3(2015)
• Page Start: 520
• Page End: 531
• Publication Date: 2014-12-10
• Subjects: NHANES -- serum folate -- 5-methyltetrahydrofolate -- unmetabolized folic acid -- HPLC–tandem mass spectrometry; Nutrition -- Periodicals; Diet -- Periodicals; 613.205
• DOI: 10.3945/jn.114.201210
• Languages: English
• ISSNs: 0022-3166

Abstract

Abstract: Background: Serum total folate consists mainly of 5-methyltetrahydrofolate (5-methylTHF). Unmetabolized folic acid (UMFA) may occur in persons consuming folic acid–fortified foods or supplements. Objectives: We describe serum 5-methylTHF and UMFA concentrations in the US population ≥1 y of age by demographic variables and fasting time, stratified by folic acid–containing dietary supplement use. We also evaluate factors associated with UMFA concentrations >1 nmol/L. Methods: Serum samples from the cross-sectional NHANES 2007–2008 were measured for 5-methylTHF ( n = 2734) and UMFA ( n = 2707) by HPLC–tandem mass spectrometry. Results: In supplement users compared with nonusers, we found significantly higher geometric mean concentrations of 5-methylTHF (48.4 and 30.7 nmol/L, respectively) and UMFA (1.54 and 0.794 nmol/L, respectively). UMFA concentrations were detectable (>0.3 nmol/L) in >95% of supplement users and nonusers, regardless of demographic or fasting characteristics; concentrations differed significantly by age and fasting time, but not by sex and race-ethnicity, both in supplement users and nonusers. The prevalence of UMFA concentrations >1 nmol/L was 33.2% overall and 21.0% in fasting (≥8 h) adults (≥20 y of age). Using multiple logistic regression analysis, UMFA concentrations >1 nmol/L were associated with being older, non-Hispanic black, nonfasting (<8 h), having smaller body surface area, higher total folic acid intake (diet and supplements), and higher red blood cell folate concentrations. In fasting adults, a decrease in the mean daily alcohol consumption was also associated with increased odds of UMFA concentrations >1 nmol/L. Conclusions: UMFA detection was nearly ubiquitous, and concentrations >1 nmol/L were largely but not entirely explained by fasting status and by total folic acid intake from diet and supplements. These new UMFA data in US persons ≥1 y of age provide much-needed information on this vitamer in a fortified population with relatively high use of dietary supplements.