Effect of increasing folic acid food fortification on dietary folate intakes and adequacy in women of childbearing age in New Zealand

Abstract

Background: Due to the weight of evidence that periconceptional folic acid use reduces the risk of neural tube defects, the New Zealand government advises women of reproductive age to take a folic acid supplement when planning a pregnancy. Similar to many other countries, supplement uptake of folic acid by New Zealand women is poor. From the mid 1990s, the government has permitted fortification of certain foods with folic acid on a voluntary basis to increase dietary folate intakes among reproductive age women. Mandatory fortification of bread with folic acid was to be implemented in 2009 but deferred and later revoked in 2012. In doing so, the government and baking industry made a commitment to increase the range of fortified bread products, with a particular focus on breads more likely to be consumed by women. There are few studies that have evaluated dietary folate intakes of reproductive age women and to date, no study has assessed whether greater adoption of voluntary bread fortification has resulted in significant improvement in usual folate intakes of this target population. Objective: The overall aim of this study was to quantify dietary folate intakes of reproductive age women prior to increased bread fortification, and to simulate the potential impact of increased folic acid fortification of bread and the proposed mandatory fortification programme on folate intake adequacy. In addition, dietary data was used to determine the major contributors of dietary folate. Design: Cross-sectional dietary analysis of 3-d weighed food record collected in 2008 from healthy reproductive age women (n=99). Usual folate intakes were calculated using nutrient values obtained from the New Zealand Food Composition Tables, which was updated using manufacturer labeled values to tabulate the folic acid, and natural food folate composition of fortified foods. Folic acid intake estimates were generated for three scenarios: i) voluntary fortification of bread based on the Manufactured Foods Database (MFD) in 2008; ii) simulated increased voluntary fortification of bread based on the MFD in 2011, and iii) simulated mandatory fortification of breads as proposed. Results: At the time of the study (before simulation), median folate intakes were 338 μg/d dietary folate equivalents (DFEs), and the prevalence of inadequacy, or the proportion of women with usual folate intakes less than their nutrient requirement was 43%. Increased voluntary fortification of breads as of 2011 is estimated to have slightly increased folate intakes to 369μg/d DFEs, producing a 9% decline in the prevalence of folate inadequacy. In contrast, simulation of mandatory fortification of breads with folic acid substantially increased folate intakes by 52% to an intake of 516μg/d DFEs, reducing the proportion of women with inadequate folate intakes to only 7%. At the time of the study, fortified breads contributed 61% of total folic acid intake followed by fortified ready-to-eat cereals (28%), yeast spreads (5%), margarine (3%) and fortified beverages (2%). Conclusion: The present study suggests reproductive age women are unlikely to meet their folate requirements from dietary sources alone, even with recent efforts to increase voluntary fortification of breads. Mandatory folic acid fortification of breads in NZ as proposed would have substantially and safely decreased the prevalence of inadequate dietary folate intake among our target population study group. The actual level of inadequacy should be determined using nationally representative survey data, with efforts directed at examining dietary intakes by income, education and ethnicity.