Modeling fortification of corn masa flour with folic acid: the potential impact on exceeding the tolerable upper intake level for folic acid, NHANES 2001–2008

Background: The Institute of Medicine set a tolerable upper intake level (UL) for usual daily total folic acid intake (1,000 μg). Less than 3% of US adults currently exceed the UL. Objective: The objective of this study was to determine if folic acid fortification of corn masa flour would increase the percentage of the US population who exceed the UL. Design: We used dietary intake data from NHANES 2001–2008 to estimate the percentage of adults and children who would exceed the UL if corn masa flour were fortified at 140 μg of folic acid/100 g. Results: In 2001–2008, 2.5% of the US adult population (aged≥19 years) exceeded the UL, which could increase to 2.6% if fortification of corn masa flour occurred. With corn masa flour fortification, percentage point increases were small and not statistically significant for US adults exceeding the UL regardless of supplement use, sex, race/ethnicity, or age. Children aged 1–8 years, specifically supplement users, were the most likely to exceed their age-specific UL. With fortification of corn masa flour, there were no statistically significant increases in the percentage of US children who were exceeding their age-specific UL, and the percentage point increases were small. Conclusions: Our results suggest that fortification of corn masa flour would not significantly increase the percentage of individuals who would exceed the UL. Supplement use was the main factor related to exceeding the UL with or without fortification of corn masa flour and within all strata of sex, race/ethnicity, and age group.