Background: The addition of folic acid to all enriched cereal-grain foods, mandated by the Food and Drug Administration (FDA), was initiated in January 1998. Although this program was designed such that typical folate intakes would be increased by approximately 100 micro g/d and that the risk of intakes > 1000 micro g/d (the FDA's safe upper limit of daily intake) would be minimal, its actual effect on folate intake has yet to be determined.
Objective: The objective was to estimate the effect of folic acid fortification on the amount of folate consumed by persons in the United States.
Design: Linear regression analysis of data from published studies was used to determine the relation between a chronic folic acid dose and the resulting increase in steady state concentrations of folate in plasma or serum. Using this regression equation and reverse prediction, we quantified the increase in folic acid intake from fortification required to achieve the increase in plasma or serum folate observed in published studies.
Results: The increase in circulating folate concentration was linearly related to folic acid intake over the range of 100-1000 micro g/d (r = 0.984, P < 0.0001). Predicted increases in folic acid intake from fortified food ranged from 215 to 240 micro g/d.
Conclusions: Typical intakes of folic acid from fortified foods are more than twice the level originally predicted. The effect of this much higher level of fortification must be carefully assessed, especially before calls for higher levels of fortification are considered.