Modelling the impact of folic acid fortification of flour on risk of neural tube defects
Folate and folic acid intake before and during pregnancy has been known for some time to have a protective effect against the development of neural tube defects (NTDs) such as Spina Bifida. Currently, however, intake for many pregnant women is inadequate, and fortification of flour or other products has been recommended by expert groups and is done in some other countries. There are, however, risks with excessive intake. Therefore, Food Standards Scotland commissioned BioSS to carry out modelling to predict the effect on intakes under various scenarios in which flour fortification might be implemented.
Graham Horgan & Claus Mayer
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Prediction modelling
The first stage was to estimate the range of intakes that could occur in various fortification scenarios. This required integrating a number of different data sources. These included a representative survey of UK dietary intakes (the National Diet and Nutrition Survey), a database of the natural folate content of all food items, and a database of the flour content of all food products which contained flour. This enabled BioSS to estimate the range of total folate (including folic acid from flour) intakes for different age and gender groups, and to assess the risks that these intakes would be either below or above the recommended limits. The prediction modelling needed to consider a number of issues, such as loss of folic acid during storage and what proportion of products would be imported without fortification.
The second stage was to use established epidemiological associations between folate intakes and NTD risks in pregnant women. The nationally representative dietary intakes, which led to predictions of the variability of folate intake, could then be combined with these risk predictions to estimate the reduction in numbers of NTD that would result from different fortification scenarios that could be considered (such as types of flour containing products to fortify and amount of folic acid added).
Using this study to inform policy
The results of the study were presented to the UK Government's Scientific Advisory Committee on Nutrition (SACN), who recommended that fortification should be implemented. On this basis, Food Standards Scotland advised the Scottish Government that fortification should go ahead, but only when it is implemented on a UK-wide basis, as it would otherwise be impractical.
