Dietary folate intake of female adolescents in New Zealand

Abstract

Background: Folate plays an important role in DNA synthesis and methylation and thus, dietary inadequacy is of particular concern primarily among reproductive age women. Studies to date show that achieving recommended dietary folate intakes can be difficult, especially in countries without mandatory folate fortification. In an effort to address this nutrient gap, the New Zealand government have instituted voluntary fortification of certain foods with folic acid (bread, breakfast cereals, fruit juice and others) since the mid-1990s. More recently, the New Zealand Association of Bakers have committed to fortifying a minimum of 25 % to 50 % of breads by sales volume, with folic acid. It is unknown whether increased bread fortification and/or changes in dietary patterns over time have influenced dietary folate intakes and the prevalence of inadequacy among the target population.

Objective: The aim of the study was to assess dietary folate intakes and major food group contributors of folate among a sample of New Zealand female adolescents aged 15 – 18 years.

Design: Healthy, female adolescents were recruited from eight high schools across the country. Sociodemographic data were collected via an online, self-administered questionnaires, and anthropometric data were collected using standardised techniques. Dietary data were collected using two non-consecutive 24-hour recalls. Usual energy and folate intakes, including natural food folate and folic acid, and the prevalence of folate inadequacy were estimated by means of dietary recalls after adjusting for intra-individual variation. Food consumption was also categorised into 33 food groups and the top dietary contributors of total folate intake were calculated.

Results: One-hundred and forty-five participants were enrolled in the study, with 132 completing dietary intake data. The average age of participants was 16.7 years, the majority were New Zealand European and Others, and 34.6 % of participants were classified as overweight and obese. Dietary results showed that the median total intake of folate was 347.2 (216.0, 430.3) µg dietary folate equivalents (DFEs)/day, and the prevalence of inadequacy was 41.7 %. A comparison of folate intakes by various socio-demographic subgroups revealed apparent differences with increased risk of inadequate intakes among participants from lower decile schools, and of Maori and Asian descent albeit sample sizes were small. Of the total folate intake in the sample population, median intake of natural food folate and food folic acid was 223.9 (161.7, 263.4) µg/day and 102.5 (75.1, 145.4) µg/day, respectively. Breads (including rolls and specialty breads) represented the top dietary contributor of total folate intake (17.7 %), followed by vegetables (10.9 %) and breakfast cereals (10.8 %). Breads were consumed by the majority of participants (81.8 %) whereas breakfast cereals were consumed less frequently by the sample population (38.6 %).

Conclusion: The overall prevalence of inadequate folate intakes was high despite consumption of folic acid fortified foods such as breads and breakfast cereals. Moreover, the results indicate that total folate intakes among reproductive age women have not increased over the last ten years despite increased voluntary folic acid fortification of breads in New Zealand. While further work is needed to recruit a more representative sample of the population, these findings raise concern regarding the effectiveness of the current voluntary folic acid fortification policy in New Zealand to meet the recommended folate requirements of female adolescents.