Periconceptional bread intakes indicate New Zealand's proposed mandatory folic acid fortification program may be outdated: results from a postpartum survey

Neural tube defects (NTD), including spina bifida, anencephaly and encephalocele, result from incomplete neural tube closure during early embryogenesis [1]. In addition to causing considerable perinatal mortality worldwide, NTD also give rise to infantile morbidity that often persists into adulthood [1]. Of all congenital malformations, NTD are among the most costly to treat, however they are unique in that more than two-thirds of cases are preventable by adequate intake of folic acid before and during the first trimester of pregnancy [1‐3]. Although accurate estimates of the total incidence of NTD are unavailable for New Zealand, the approximate rate at birth is seven cases per 10,000 [4]. This rate is 40% higher than the lowest NTD birth prevalence estimated to be attainable with sufficient folic acid intake [5].

While mandatory fortification interventions provide a lower dose of folic acid than the issued supplement recommendation of 400 μg/d, existing programs have proven successful in both raising reproductive-aged women's red cell folate and reducing the incidence of NTD [6‐9]. Moreover, mandatory folic acid fortification of a staple food delivers folic acid to those who may not otherwise commence folic acid supplementation preconceptionally, such as women with unplanned pregnancies [10]. In New Zealand, voluntary folic acid fortification of specified foods has been permitted since 1996, with breakfast cereals and wholegrain breads making up the majority of currently fortified food items [11]. The addition of folic acid to all yeast-leavened, non-organic bread was to be mandated in September 2009 at a level of 135 μg folic acid/100 g bread [11]. Using nationally representative data from a food consumption survey conducted in 1997, this fortification level was selected with the aim of achieving optimal effectiveness and safety [11]. The 1997 survey reported a daily median bread intake of 3-4 slices among reproductive-aged women, and the fortification level was intended to increase mean folic acid intakes of this group by 140 μg/d [11]. However, due to political and manufacturer objection, mandatory fortification was deferred until May 2012, with no guarantee of implementation [12].

Although bread was the chosen vehicle for fortification in New Zealand, little is known about the current bread consumption patterns of childbearing women prior to and during pregnancy. Moreover, no previous studies have determined the potential impact of fortification on folic acid intakes by age, socioeconomic status and ethnicity to evaluate whether the program would have a meaningful impact on all segments of the target population. This is particularly important given socio-demographic disparities in periconceptional folic acid supplement use reported in New Zealand [10], Australia [13], and elsewhere [14‐16]. Therefore, we assessed bread consumption among women prior to and during pregnancy with the intent to estimate periconceptional folic acid intakes that would be derived from bread if mandatory fortification were implemented as currently proposed.

Nearly 15 y have elapsed since the collection of data upon which New Zealand's current mandatory fortification proposal is based, and our data indicates bread consumption has decreased markedly from a median of 3-4 slices/d to 2 slices/d in the target group of childbearing-age women. If mandatory fortification is implemented as proposed, we estimate the age- and ethnicity-weighted mean additional folic acid intake to be 119 μg/d among women prior to pregnancy, well below the intended 140 μg/d. Given the bread consumption data collected in this study, to achieve the targeted additional intake of 140 μg/d, a mandatory fortification level of 160 μg folic acid/100 g bread may be required. Nonetheless, the results of our study indicate that the least advantaged segments of the target population will benefit from the mandate if implemented as currently proposed. Additional folic acid intakes were shown to be greatest among Pacific and indigenous Māori ethnic groups, those with increased parity, lower income and education, younger and single mothers and women with unplanned pregnancies. Conversely, subgroups predicted to derive the least benefit from the proposed bread scheme are women of Asian descent and those with a postgraduate education.

Despite a non-binding agreement from the bread industry in 2009 to increase the number of voluntarily fortified breads, few breads in New Zealand contain added folic acid [26]. Fortified breads are typically wholegrain, which may not be readily affordable for women of lower socioeconomic status [26]. In the 2008/2009 Adult Nutrition Survey, women living in the most deprived neighborhoods were less likely to regularly consume wholegrain bread than those in the least deprived neighborhoods, and the overall proportion of women regularly consuming wholegrain bread declined linearly with decreasing age [27]. The other main source of dietary folic acid in New Zealand is voluntarily fortified ready-to-eat breakfast cereals [11]. In the 1997 National Nutrition Survey, those living in areas of greatest socioeconomic deprivation and Māori and Pacific people consumed the least servings of cereals (including breakfast cereals) per week [28]. Disparity in the consumption of voluntarily fortified foods is also apparent in current estimates of dietary folic acid intake. From voluntarily fortified sources, the mean intake of folic acid among New Zealand women is estimated to be 58 μg/d. Comparatively, the median intake is estimated to be 21 μg/d, suggesting that many women consume close to nil folic acid from voluntarily fortified foods [11]. Here, we are able to show that the proposed bread fortification mandate would remedy these identified socio-demographic inequities in dietary folic acid intake, with young women, Māori and Pacific women and those with lower household incomes benefiting markedly from the proposed scheme. Recommended periconceptional folic acid supplement use is also lower among these groups, ranging from 2.7% among Pacific women, 9.2% among Maori women, and 7% among women reporting an annual household income of less than 40,000 NZ$ [10]. This further underscores the benefit of mandatory fortification in reducing inequities in folic acid intake. To our knowledge, no published data on the rate of NTD among different ethnic groups in New Zealand exists post-introduction of periconceptional folic acid supplementation recommendations. However, reports from the late 1970's and early 1980's indicate that the rate of NTD was lower among Pacific and Māori women compared with non-Māori [29].

Although fortification is shown to be effective at reaching a wide range of individuals, it should be highlighted that 14% of all women either consumed no bread in the periconceptional period, or consumed only organic or homemade bread, which are exempt under the current proposal. Where all enriched cereal-grain products are fortified in the US at 140 μg folic acid/100 g flour, bread has been proposed as the solitary food vehicle for mandatory fortification in New Zealand [11, 30]. While having greater tractability for monitoring purposes, bread fortification will not benefit those who consume little or no bread, and will likely result in lower folic acid intakes than if all cereal-grain products were fortified. In the US, a median folic acid intake of 117 μg/d was reported among adult women whose folic acid intakes were exclusively derived through the consumption of mandatorily fortified cereal-grain products [30]. Our estimated median additional intake of 89 μg folic acid/d among New Zealand women prior to conception is substantially lower. At a higher fortification level of 160 μg folic acid/100 g bread, we predict a median additional intake of 106 μg/d, closer to that of US women.

In addition to bread, mandatory folic acid fortification of further food products may be needed to target specific population subgroups. For example, Asian women were estimated to attain a mean additional folic acid intake 30 μg/d below the overall mean, indicating that this subgroup is targeted less effectively under the proposed program. Acculturation may influence bread consumption [31], as Asian women born outside of New Zealand consumed approximately one slice of bread less per day than those born in New Zealand. A recent Auckland-based study found that Asian women also consumed fewer servings of ready-to-eat breakfast cereal than New Zealand Europeans, placing this group at further risk of poor folic acid intakes [32]. Other potential cereal-grain fortification vehicles, such as rice and noodle products, are predominantly imported into New Zealand and are therefore not readily amenable to mandatory fortification. Fortification of eggs is a possible alternative [33], with egg intake among Asian women reported to be significantly higher than among New Zealand Europeans [32]. Compared to New Zealand Europeans, periconceptional folic acid supplement use is also lower among Asian women [10], further identifying this group as being at high-risk of suboptimal folic acid intakes.

Internationally, mandatory folic acid fortification interventions are based on country-specific target intakes, risk-assessment and consumption patterns, and range from 140-220 μg folic acid/100 g cereal-grain product [34]. Our proposed fortification level of 160 μg folic acid/100 g bread to achieve a targeted mean additional intake of 140 μg/d in childbearing-age women is therefore not unreasonable, although dietary modeling for the entire population would be necessary to ensure folic acid intakes remain within acceptable levels. In Australia, folic acid intakes from voluntarily fortified foods are estimated to be higher than those in New Zealand, and mandatory folic acid fortification of bread (200 μg per 100 g flour, equivalent to 120 μg per 100 g bread) was introduced in September 2009 [11]. Mean red cell folate levels measured in a large sample of Australians undergoing diagnostic blood tests increased from 881 nmol/L prior to mandatory fortification to 1071 nmol/L in the year ended April 2010 [35]. In a randomised controlled trial designed to mimic intended folic acid intakes of the proposed fortification program in New Zealand, participating reproductive-aged women had a baseline mean red cell folate level of 753 nmol/L [36]. Following 40 weeks folic acid supplementation at 140 μg/d, mean red cell folate levels rose to 1111 nmol/L [36]. These findings show that mandatory folic acid fortification in Australia at the current level and in New Zealand at its intended intake level (140 μg/d) is successful in raising red cell folate levels to those associated with the maximal reduction in NTD risk (906 nmol/L) [37].

Several limitations in our study merit discussion, such as its retrospective design with reliance on memory of past bread intake. Moreover, we did not formally validate our survey questions for assessing the habitual bread consumption over the defined periods of time. Underreporting of energy intakes occurs more frequently among non-pregnant women than men, and underreporting of energy intakes in pregnancy has recently been correlated with socio-demographic status [38]. Underreporting of bread consumption may thus have lead to an underestimation of folic acid intakes, which may have occurred differentially according to socio-demographic subgroup, potentially attenuating or exacerbating estimated differences in folic acid intake between groups. However, the anonymous, self-administered nature of the survey and its completion prior to discharge may have lessened under-reporting and incorrect recall, respectively. In addition, retrospective nutrient intakes in pregnancy have been reported elsewhere to have a validity similar to those conducted in the general populace [39]. While a lower proportion of Māori and Pacific women participated than would be expected given national data, this was due to the non-inclusion of hospitals in the Northland region, where a large proportion of people identifying themselves as Māori and Pacific reside [40, 41]. Weighting by age and ethnicity resolved these differences in ethnic representation, thus there are no reasons to expect this to have affected our estimation of folic acid intakes.

Mandatory fortification of enriched cereal-grain products in the US has been highly effective in reducing the incidence of NTD [8]. In two large US case-control studies, it has recently been found that supplemental folic acid does not confer any further benefit in the prevention of NTD, suggesting an optimum habitual intake has been reached [42, 43]. In New Zealand, mandatory bread fortification would deliver substantial additional folic acid intakes to socio-demographic subgroups of women where consumption of voluntarily fortified foods and folic acid supplement uptake during the periconceptional period is insufficient. As many countries worldwide continue to debate mandatory folic acid fortification, this study provides insight on the ability of such a policy to benefit the groups at highest risk of poor folate intakes in a population. Nonetheless, in light of the finding that not all subgroups may benefit equally, this study underscores the importance of monitoring actual folate intakes and status in the target population should fortification be mandated. Bread consumption among reproductive-aged women appears to have declined since the data used in previous dietary modeling were collected. It would therefore be prudent to re-model population-wide folic acid intakes using more recent national survey data to assess the impact of the proposed fortification policy prior to its implementation.