Abstract
Background: Magnesium is an essential mineral to the human body. During adolescence, rapid rates of growth are accompanied with an increase in nutritional demand for magnesium. Despite its abundance, intakes among adolescent males have been found to be inadequate in many countries. The National Nutrition Survey (NNS) in 1997 found intakes within New Zealand to be adequate, but key dietary sources were not identified. In the later Adult Nutrition Survey (ANS), magnesium intakes were not reported. Due to changes in the food supply, technological developments, consumer preference and behaviours over time it is important to update the information concerning intakes and dietary sources of magnesium for the New Zealand adolescent male population.
Objective: The aim of this study was to investigate the magnesium intakes and the main dietary sources among the adolescent male (15-18y) population of New Zealand.
Methods: 135 participants were recruited from six schools across Dunedin, Wellington, Christchurch, Rotorua, Tauranga and Auckland. Participant demographics, health information and dietary habits were assessed through self-administered online questionnaires. Anthropometric measurements were taken and used to assign a BMI-z score to participants. Dietary intake was assessed using two non-consecutive 24-hour recalls. These were performed using a three-pass multiple pass method. Recalls were entered into the dietary analysis software, FoodWorks 9, which was used to calculate energy, macronutrients and micronutrients intake. Foodworks 9 used the 33 food groups included in the Adult Nutrition Survey to identify the main dietary sources of magnesium. Estimation of usual intakes was done using the multiple source method (MSM) programme. The EAR cut point method was used to estimate the prevalence of inadequate intakes within the convenience sample.
Results: Participants had an average age of 16.6 years (SD=0.7) and a BMI z score of +0.4 (SD=1.1). Participants predominately identified as New Zealand European or Other (57%). Based on the 2018 New Zealand Deprivation categories, participants mostly came from moderate levels of deprivation (42%). At least one 24-hour dietary recall was completed by 102 participants. The average median intake of magnesium was 318.3mg/day (25th percentile=259.7, 75th percentile= 364.9) with 61.8% of participants consuming intakes below the estimated average requirement (EAR). The five main dietary sources of magnesium were bread (10.4%), grains and pasta (10.2%), milk (8.9%), poultry (7.7%) and fruit (6.4%). Collectively the food groups ‘grains and cereals’ (26.5%) provided the greatest source of magnesium to participants followed by vegetables and fruit (18.7%), meat, fish, poultry and eggs (16.2%), and milk and milk products (11.9%).
Conclusion: Despite consuming magnesium from a variety of sources, approximately 61.8% of participants consumed intakes below the recommended EAR (340mg/day). This aligns with global literature, which frequently estimates 60-70% of adolescent males consume inadequate intakes. Due to the immediate and subsequent health implications of low magnesium intakes, action to resolve suboptimal intakes may be required. This may include interventions at an individual level (e.g. education) or national level (e.g. fortification, supplementation, subsidies and tax). To justify any action, research using a nationally representative sample is warranted to investigate magnesium intakes and main dietary sources of New Zealand adolescent males.