Abstract
Background: Folate is a B vitamin involved in the synthesis and methylation of deoxyribonucleic acid (DNA). Green leafy vegetables, citrus fruits, liver, yeast extracts and whole grains are rich sources of natural folate. Synthetic folic acid is commonly added to foods including cereals, breads and beverages. Inadequate folate intake is common amongst females, particularly in countries that do not allow, or only permit voluntary folic acid fortification. Currently, New Zealand permits folic acid fortification on a voluntary basis, however, the debate over mandatory versus voluntary fortification is ongoing.
Objective: To investigate and compare the dietary intake of, and major food group contributors of folate (including folic acid) among adolescent males and females aged 15- 18 years in New Zealand.
Design: This study is part of SuNDiAL (Survey of Nutrition, Dietary Assessment and Lifestyle), a New Zealand-wide observational, cross-sectional survey. Participants aged 15-18 years were recruited from 19 high schools across New Zealand in 2019 and 2020.
Socio-demographic, anthropometric and dietary data, including food frequency and dietary habits questionnaires, were collected. Usual dietary folate intakes were assessed using two 24-hour diet recalls completed on non-consecutive days. Dietary folate was reported as total folate (dietary folate equivalents, DFEs), natural food folate and folic acid. The EAR cut off of 330 µg/day DFE was used to determine the prevalence of inadequacy. Lastly, the major food groups that contributed to total dietary folate intake were assessed and ranked.
Results: Four-hundred and two participants enrolled in the study comprised of 266 females and 135 males, with a mean (SD) age of 17 (0.8) years. The majority of participants identified as New Zealand European and other (NZEO) (71%) followed by Maori, Asian and Pacific. The median (IQR) of total usual dietary folate intake of male participants was 453.9 (334.1,714.9) µg DFEs/day and for females was 408.7 (299.4, 585.8) µg DFEs/day, resulting in a prevalence of inadequate intake of 25% and 33%, respectively. Male participants had nearly double the intake of folic acid compared to that of females (77.0 and 41.6 µg/day, respectively). Differences in total folate intake and prevalence of inadequacy between males and females were more apparent in the older age groups (17-18 years) with females having double the risk of inadequacy compared to their male counterparts (32% vs 16% respectively). For all females, the highest prevalence of inadequacy was reported in participants classified as Asian (67%) and those from higher socio-economic neighbourhoods (44%).
Among males, participants who identified as Asian (35%) and Pacific (33%) had the highest prevalence of inadequate intake. The top food groups contributing to folate intake in males was breakfast cereals at 25% and bread in females at 17%.
Conclusion: Overall, both males and females were at risk of inadequate folate intakes although the prevalence of inadequacy was concerningly higher among females. The major food groups contributing to dietary folate intakes were predominantly fortified food products although folic acid intakes were moderate. Further food fortification measures may be needed to meet the intake requirements of this lifecycle group, however, nationally representative survey data would enable better modelling and risk assessment.