Zinc intakes and main food sources of zinc in New Zealand adolescent females

Abstract

Background: It has been proposed that New Zealand (NZ) adolescent females are currently going through a dramatic change in food selection patterns. Due to this, there have been concerns around the adequacy of zinc intake in these young women. The research in NZ on zinc intake and its main food sources in adolescent females is currently limited to only one nationally representative survey conducted a decade ago.

Objective: The aim of this thesis was to describe the zinc intake of adolescent females 15-18 years of age in NZ. The objectives were to: 1) determine the zinc intake of NZ adolescents 15-18 years of age, 2) determine the prevalence of inadequate and potentially excessive intakes of zinc in NZ female adolescents at 15-18 years of age using diet and supplemental intake data, and 3) identify key food sources of zinc for NZ female adolescents at 15-18 years of age.

Design: The Survey of Nutrition Dietary Assessment and Lifestyle (SuNDiAL) project is a cross-sectional survey of adolescent females 15-18 years of age (n=145) recruited from eight secondary schools between February and March 2019. The Candidate collected data from a subset of these participants. Data from all participants are reported in the thesis. Online self-administered questionnaires were used to collect data on participants’ demographics, health and supplement use. Following this, participants attended three appointments over the course of two weeks where height and weight were measured and two 24-hour recalls were conducted. Data from the 24-hour recalls were analysed using the dietary software programme FoodWorks to calculate zinc intakes and the main food sources of zinc in the diet.

Results: The majority of the study participants appeared to have an adequate intake of zinc with a mean dietary zinc intake of 9.3mg/day and a median total zinc intake of 9.2mg/day when dietary and supplemental zinc intake was combined. In total, 10.6% of participants were at risk of inadequate zinc intake and one participant had an excessive intake when using the Australian and NZ age-specific Estimated Average Requirement and Upper Level of Intake for females. ‘Grains and pasta’ was the primary food source of zinc intake contributing 10.9%, followed by ‘bread-based dishes’ and ‘bread’, at 9.3% and 8.1% respectively. In an additional analysis, there was only one significant association found between dietary zinc intake and characteristics measured in the study: students who attended the school from the lowest school decile had a significantly lower zinc intake on average than students from the highest decile schools (p=0.010).

Conclusion: These findings are consistent with current NZ and Australian literature which suggest that the majority of adolescent females are consuming an adequate zinc intake. However, we cannot conclude that zinc is not a nutrient of concern in the NZ adolescent female population based on dietary zinc alone. Further research should assess the biochemical zinc status of this age group of young women, in order to determine whether these dietary zinc intake data reflect zinc status.