Updated Data On Estimated Folate Intake

Nutrition Research Newsletter, Sept, 1999 by Christine J. Lewis, Nancy T. Crane, Dennis B. Wilson, Elizabeth A. Yetley

While folic acid continues to raise controversy, the National Academy of Sciences' Institute of Medicine (IOM) has published a report establishing dietary reference intakes (DRIs) for folate and several other B vitamins. This report includes an estimated average requirement (EAR: an intake below which inadequate intake may be a concern), a recommended dietary allowance (RDA), and a tolerable upper intake level (UL) for folate. The IOM report used data from the 1994-1996 Continuing Survey of Food Intakes by Individuals (CSFII) and the Third National Health and Examination Survey (NHANES III), but acknowledged that the estimates were incomplete.

The FDA, US Department of Agriculture, and the National Center for Health Statistics of the Centers for Disease Control and Prevention chose to conduct a study to provide updated estimates of total folate intake that would account for the missing components of the IOM report. Specifically, these agencies focused on the increased contribution of synthetic folic acid (SFA) from food fortification and dietary supplements, and from adjustments made for its greater bioavailability than that of naturally occurring folate (NF).

The above surveys were completed before the policy implementing folate fortification was in place. Therefore, the food composition databases do not reflect the increase in folate intake as a result of the fortification, and adjustments were made to the data by using information about food ingredients. After being revised, the databases included lists of amounts of SFA in each food reported. Total folate intakes were estimated for several sex and age groups by using the modified data coupled with dietary supplement use.

The results of the study suggest that 67-95% of the population met or surpassed the new estimated average requirement for folic acid. Only approximately 25% of women of childbearing age achieved this goal, and the percentage was lower in younger females. However, in all cases, the modifications made to the data resulted in higher folate intakes, as expected. A more dangerous piece of evidence was that 15-25% of children aged one to eight years old had intakes above the newly established UL.

The researchers acknowledge potential sources of error in this study. The procedure for updating folate intakes undoubtedly introduced some errors since a food-by-food analysis to determine folate content in fortified foods could not be conducted. Also, as recognized in many other studies, data from food consumption surveys typically underestimates the amount of food consumed, while the amount of folic acid intake from supplements is unknown.

The purpose of this study was to monitor total folate intakes to ensure a safe and adequate food supply. The results suggested that folate intakes of a majority of the US population were fairly comparable to the IOM standards. However, toddlers and young children should be closely monitored in relation to the tolerable upper intake levels. As reported in previous studies, further information is needed to determine an effective way of improving folate intakes in females of childbearing age to prevent against neural tube defects.

Christine J. Lewis, Nancy T. Crane, Dennis B. Wilson, and Elizabeth A. Yetley, Estimated Folate Intakes: Data Updated To Reflect Food Fortification, Increased Bioavailability, and Dietary Supplement Use, Am J Clin Nutr, 70(2): 198-207 (August 1999) [Correspondence: C. J. Lewis, Food and Drug Administration, HFS-451, 200 C St. SW, Washington, DC 20204. E-mail: Clewisl@bangate.fda.gov.]