Abstract
Background: It is well established that protein is an important macronutrient required by the body to support a variety of biological functions. In particular, adequate protein intakes play a significant role in pubertal growth. However, recent data on protein intake and its food sources is scarce and in New Zealand is limited to a national survey that was conducted more than a decade ago.
Objective: This thesis aims to investigate protein intake, determine the dietary sources of protein, as well as evaluating the adequacy of protein intake among New Zealand male adolescents.
Design: The Survey of Nutrition Dietary Assessment and Lifestyle (SuNDiAL) project is a cross-sectional study involving 135 male adolescents aged 15-17 years from six high schools across New Zealand. Participants completed a self-administered online questionnaire on demographics and dietary habits. An interviewer assisted 24-hour dietary recall (24-HDR) was carried out during in-school visits, where anthropometric measurements were also taken. Body mass index (BMI) z-scores were calculated to assess body weight status. A second 24-HDR was carried out a week later through phone/ video call to account for intra-individual variation. FoodWorks software (FOODfiles 2016- Version 01) was used for nutrient analysis and the multiple source method was applied to adjust data for mean intake. Prevalence of inadequate protein intakes were determined by calculating the percentage of participants with intakes below the estimated average protein requirement of 49 g/d and 0.76 g/kg/d as per National Health and Medical Research Council recommendations.
Results: Mean protein intake was 110 g/d (95%CI 104, 115); 1.63 g/kg/d (95%CI 1.54, 1.72). All participants had intakes that met the Estimated Average Requirement (EAR) of 0.76 g/kg/d recommended by the National Health and Medical Council. Participants with a healthy weight had significantly higher protein intakes of 1.73 g/kg/d (95%CI 1.63, 1.84) compared to obese participants 1.11 g/kg/d (95%CI 0.88, 1.34); however, only 3 respondents were obese. The average protein contribution to total energy (TE) was 18.6%. The majority of participants (86.7%) had intakes within the Acceptable Macronutrient Distribution Range of 15-25%, with 13.7% below the range and 1% exceeding the range. The five main protein food sources were poultry (16.4%), grains and pasta (11.3%), milk (8.3%), bread (8.2%) and bread-based dishes (7.4%). Based on the dietary habits questionnaire, one-fifth of participants (22.1%) reported consuming sports supplement with 77.7% of those reporting using a supplement containing whey protein.
Conclusion: These findings suggest that protein intake is adequate among 15-17 year old New Zealand male adolescents. Further research using a larger, more representative sample is required to determine the association between protein intake and demographic characteristic.