Enquobahrie, DanielFeldman, HenryHoelscher, DeannaSteffen, LynWebber, LarryZive, MichelleRimm, Eric Bruce::0ab2926c8242f35e5a982e3cf59f4987::600Stampfer, MeirOsganian, Stavroula2019-08-262012Enquobahrie, Daniel A, Feldman, Henry A, Hoelscher, Deanna H, Steffen, Lyn M, Webber, Larry S, Zive, Michelle M, Rimm, Eric B, Stampfer, Meir J, Osganian, Stavroula K. 2012. 'Serum homocysteine and folate concentrations among a US cohort of adolescents before and after folic acid fortification.' Public Health Nutrition 15, 10: 1818-1826. https://doi.org/10.1017/S13689800120029841368-98001475-2727http://nrs.harvard.edu/urn-3:HUL.InstRepos:41247227Objective: We assessed serum homocysteine (tHcy) and folate concentrations among US adolescents before and after fortification of cereal-grain products with folic acid, and associations with demographic, behavioural and physiological factors. Design: Observational study conducted among participants of a randomized trial. Setting: The Child and Adolescent Trial for Cardiovascular Health (CATCH) study.Subjects: Adolescents (n 2445) in grades 8 (pre-fortification, mean age 14 years) and 12 (post-fortification, mean age 18 years). Results: Average serum concentrations of tHcy, folate and vitamin B-6 increased by 17%, 16% and 14%, respectively, while serum concentrations of vitamin B-12 decreased by 11% post-fortification. Folic acid fortification provided, on average, an additional intake of 118 mu g folate/d. Male sex (P < 0.0001) and white race (P = 0.0008) were associated with significantly greater increases in tHcy concentration, while increases in BMI (P = 0.006) and serum folate concentration (P < 0.0001) were associated with significant decreases in tHcy concentration. Female sex (P < 0.0001), non-smoking (P < 0.0001), use of multivitamins (P < 0.0001) and higher dietary intake of folate (P = 0.001) were associated with significantly greater increases in serum folate concentrations. From grade 8 to grade 12, the upward age trend in serum tHcy concentration was uninterrupted in its course (P > 0.50); whereas serum folic acid concentration showed a downward trend that incurred a discrete jump upward (17% higher; P < 0.0001) with fortification. These trends differed significantly for males v. females (P < 0.001 for interaction). Conclusions: Fortification had a significant impact on improving folate status but not serum tHcy concentrations among US adolescents.en-USJournal Article2019-08-2610.1017/S1368980012002984