Impact of voluntary fortification and supplement use on dietary intakes and biomarker status of folate and vitamin B-12 in Irish adults

Background: Ireland has traditionally operated a liberal policy of voluntary fortification but little is known about how this practice, along with supplement use, affects population intakes and status of folate and vitamin B-12. Objective: To examine the relative impact of voluntary fortification and supplement use on dietary intakes and biomarker status of folate and vitamin B-12 in Irish adults. Design: Folic acid and vitamin B-12 from fortified foods and supplements were estimated using brand information for participants from the cross sectional National Adult Nutrition Survey 2008-10. Dietary and biomarker values were compared across six mutually exclusive consumption groups formed on the basis of folic acid intake.Results: Consumption of folic acid through fortified foods at low, medium and high levels of exposure [median intakes (IQR) of 22 (13,32), 69 (56, 84) and 180 (137,248) µg/d respectively], supplements [203 (150,400) µg/d] or both [287 (220,438) µg/d] was associated with significantly higher folate intakes and status compared to non-consumption of folic acid (18% of the population). Median (IQR) red blood cell (RBC) folate increased significantly from 699 (538,934) nmol/L in non-consumers to 1040 (83, 1390) nmol/L in consumers with a high intake of fortified foods (P<0.001) with further non-significant increases in supplement users. Supplement use but not fortification was associated with significantly higher serum vitamin B-12 concentrations relative to non-consumers (P<0.001). Two thirds of young women had suboptimal RBC folate for protection against neural tube defects (NTDs); among non-consumers of folic acid only 16% attained optimal RBC folate.Conclusion: Consumption of voluntarily fortified foods and/or supplement use was associated with significantly higher dietary intakes and biomarker status of folate in Irish adults. Of concern, the majority of young women remain sub optimally protected against NTDs.