Dietary intake and food sources of protein among adolescent females aged 15-18 years living in New Zealand

Abstract

Background: Adolescence is a life stage characterised by rapid physical growth and development. These rapid changes increase the requirement for protein and energy (1). Protein has a functional and structural role in the body where it makes up a large proportion of skeletal muscle and many other body cells. Protein is, therefore, an important macronutrient during this period of considerable growth. Recent data regarding the dietary protein intake and major protein food sources among this population group is scarce. The aim of this thesis, is to investigate the dietary intake and major food sources of protein for adolescent females aged 15-18 years of age living in New Zealand. Design: This cross-sectional, clustered study collected information regarding demographics (age, sex, and ethnicity) and nutritional supplement use via online questionnaires. Dietary intakes of all food and beverages were assessed by two non-consecutive 24-hour diet recalls. Data from these diet recalls were entered into FoodWorks and were matched to nutrient lines from the 2016 New Zealand FOODfiles to calculate dietary protein intake. Usual dietary protein intake was calculated using the multiple source method. Height and weight was measured using standard protocols and used to calculate body mass index z-scores. Results: Data was available for 145 adolescent females aged 15-18 years, who were enrolled in one of the eight secondary schools visited throughout New Zealand. The mean daily intake of protein for adolescent females aged 15-18 years was 73.7g (95% CI 70.1, 77.3). The mean intake of protein expressed per kilogram of body weight per day was 1.2g/kg/d (95% CI 1.1,1.2). Both the mean daily intake and g/kg/d were adequate in meeting the EAR of 45g/d and 0.62g/kg/day respectively. Eleven (8.5%) participants had an inadequate intake of protein defined as <0.62g/kg/d. Protein intake contributed on average 15 % (95% CI 14.9,16.0) of the total energy intake, which was at the lower end of the acceptable macronutrient distribution range (15-25%). No significant association was observed between protein intake and ethnicity; however, the prevalence of inadequate protein intakes was significantly greater in participants who were classified as overweight or obese. Poultry was the single largest contributor of dietary protein (12.5%), followed by, bread-based dishes (9.7%), bread (8.5%) and grains and pasta (8.4%). Conclusion: These findings show that the usual dietary protein intakes of healthy adolescent females aged 15-18 years living in New Zealand are adequate. This, along with the confirmation that both animal and plant-based foods contribute to protein intake in this population, will assist the review of dietary guidelines and recommendations for this age group. Further work is required to confirm the preliminary finding that overweight and obese adolescent females are more likely to have inadequate protein intakes.