Dietary intake, adequacy and food sources of zinc in New Zealand adolescent males and females

Background: Zinc is an essential trace mineral and plays a role in immune function, wound healing, and normal growth and development. Evidence suggests that the risk of inadequate zinc intakes during adolescence – a period of rapid growth – is moderate to high. The recent global shift towards vegetarian diets and lower bioavailability of zinc from plant foods than that from animal foods may further increase the risk of suboptimal intakes. With the latest New Zealand nutrition survey conducted over 10 years ago, zinc intakes among New Zealand adolescence are unknown. Objective: To describe and assess the usual intakes of, and main food groups contributing to zinc intake among New Zealand adolescent males and females. Design: The Survey of Nutrition Dietary Assessment and Lifestyle (SuNDiAL) project was a two-year cross-sectional survey of 401 adolescent males and females aged 15-18 years old. In Year 1, 266 females were recruited from thirteen schools in eight locations around the country with a targeted approach to recruit vegetarians. In Year 2, 135 males were recruited from six schools in five locations around the country. A total of 28 female and five male vegetarians were included in the study. Socio-demographics and health, dietary habits, and attitudes and motivations to food choice were collected via an online questionnaire. Anthropometrics were collected using standardized study protocols. Two non-consecutive 24-hour diet recalls were used to assess dietary intakes. Usual zinc intakes were estimated using the MSM method. The prevalence of zinc inadequacy was determined using the estimated average requirement (EAR) cut-point method (11 mg/day for males and 6 mg/day for females). The major food groups contributing to zinc intake were calculated from 33 food groups. Results: The usual median (IQR) zinc intake for males was 13 (10.3, 15.2) mg/day and 9 (7.3, 10.6) mg/day for females. Overall, the prevalence of inadequate zinc intakes was relatively low for females (6.4%) but substantially higher for males (23%). For males, the highest prevalence of inadequacy existed among Māori and Pacific sub-groups and those that resided in moderate-high deprivation areas. For females, Māori and Asian participants appeared at greatest risk of suboptimal zinc intakes. Apparent differences in the prevalence of zinc inadequacy existed among vegetarian males (20%) and females (7%), despite no differences existing among vegetarian and non-vegetarian within each sex group. ‘Grains and pasta’ were the greatest dietary contributor to zinc intakes for both males and females, followed by bread and bread-based dishes for females and poultry and beef and veal for males. Conclusion: Males appear to be at a greater risk of inadequate zinc intakes compared to females with some sub-groups at greater risk than others. There were no apparent differences between vegetarians and non-vegetarians despite other studies reporting a high risk of inadequate zinc intakes among vegetarians. The number of participants identifying as vegetarian limited interpretation, and further research is warranted to confirm findings