Increasing evidence in favour of mandatory fortification with folic acid

Folic acid fortification of grain foods on a mandatory basis has been in place in the USA since 1998. Because of the safety concerns surrounding this issue, the Food and Drug Administration in the USA, responsible for implementing the new fortification legislation, opted for the relatively low folic acid concentration of 1400mg/kg product, (United States Department of Health and Human Services, Food and Drug Administration, 1996). This level of folic acid was projected to result in a mean additional intake of 100mg/d in the US population and was considered low enough to almost certainly carry no risk, but some argued that it would turn out to be ineffective in preventing neural tube defects (NTD). However, evidence just published indicates that the incidence of NTD in the USA has declined by almost 20 % as a result of the new folic acid fortification policy (Honein et al. 2001). These results will undoubtedly renew pressure on the UK government to implement a similar policy. Mandatory folic acid fortification for the UK was in fact proposed last year by the Government’s Committee on Medical Aspects of Food and Nutrition Policy (COMA; Department of Health, 2000). Since its publication, the COMA report has been undergoing consultation, being undertaken jointly by the four UK Health Departments and the Foods Standards Agency. The main conclusion of the report was that: ‘universal folic acid fortification of flour at 240mg/100 g in food products as consumed would have a significant effect in preventing NTD-affected conceptions and births without resulting in unacceptably high intakes in any group of the population’. The recommended fortification level of 240mg/100 g flour (2400mg/kg flour) has been estimated to increase mean folic acid intakes by 200mg/d which, in turn, is predicted to reduce the incidence of NTDaffected pregnancies by 41 %. The report puts this reduction into context (based on 1997/1998 NTD data), as being equivalent to the prevention of thirty-eight of the ninetythree NTD-affected births in England and Wales, thirty of the seventy-four in Scotland, and six of the fourteen in Northern Ireland. Although the report focused primarily on the proven role of folic acid in the prevention of NTD, the potential benefit of folic acid in reducing the risk of cardiovascular disease via homocysteine-lowering (Boushey et al. 1995) was also acknowledged. The conclusions of the recent COMA report (Department of Health, 2000) were based on a detailed risk–benefit assessment. Such an assessment, which estimates the likely benefits of folic acid fortification in terms of NTD reduction, as well as the risk of overexposure in those with high intakes, requires the manipulation of a representative dietary survey database, sometimes referred to as dietary modelling. In the COMA report, estimates of the exposure of different groups in the population to additional folic acid were made by modelling dietary intake data from four National Diet and Nutrition Surveys for each age group, at five possible levels of fortification of flour as consumed in finished products: 1400mg/kg; 2000mg/kg; 2400mg/kg; 2800mg/kg; 4800mg/kg. At each of these fortification levels, an estimation was provided as to the number of NTD-affected births per year which would be prevented, as well as the percentage of people over 50 years who would be exposed to a folic acid intake greater than 1 mg/d (equivalent to the upper tolerable intake level). The concern here primarily relates to the potential masking of the anaemia (and therefore the possibility of delaying the diagnosis) of vitamin B12 deficiency amongst older people exposed to high folic acid intakes. The other key strength of the risk–benefit assessment performed by COMA (Department of Health, 2000) was the availability of good data by which the additional folic acid intake at the various fortification levels could be related to NTD risk. For this purpose the placebo-controlled trial of Daly et al. (1997) was used. This study predicted the effects on NTD risk of folic acid intervention at 100, 200 or 400mg/d administered over a 6-month period, on the basis of the responses of red cell folate concentration, which had previously been established to relate to NTD risk in a continuous dose–response inverse relationship (Daly et al. 1995). The reliability of this approach as a basis for predicting NTD risk has now been confirmed by the recent US evidence. Daly et al. (1997) predicted a 22 % reduced risk of NTD arising from the US fortification programme delivering an additional 100mg/d folic acid. This compares very closely with the actual US experience reported by Honein et al. (2001) in which NTD reported on birth certificates fell from 37:8 per 100 000 live births before fortification to 30:5 per 100 000 live births after fortification, representing a 19 % decline in NTD. The incidence of spina bifida fell by 23 %. Thus, there can be a good degree of confidence in COMA’s predicted 41 % reduction in the incidence of NTD-affected pregnancies arising from the recommended fortification level of 2400mg/ kg flour; projected to deliver an additional 200mg/d folic acid in the UK (Department of Health, 2000). The paper by Moynihan et al. (2001) in the present issue of the British Journal of Nutrition is timely and will contribute to the current folic acid fortification debate. The study employs dietary modelling of a 1990 dietary survey of 379 Northumberland schoolchildren aged 11–12 years to predict the consequences on the folic acid intake of adolescents if flour were fortified at the recommended level of 2400mg/kg (Department of Health, 2000). Of concern, in the absence of mandatory fortification, a substantial proportion of these schoolchildren (7 % girls, 10 % boys) failed to achieve even the lower reference nutrient intake for British Journal of Nutrition (2001), 86, 425–426 DOI: 10.1079/BJN2001440 q The Author 2001