Abstract
Background: Adolescence is a period of rapid growth and thus, is an essential time for ensuring adequate intake of all nutrients. Vitamin B12 in particular, is an essential nutrient for DNA synthesis, red blood cell formation and neurological function. Based on data from the 2008/09 New Zealand Adult Nutrition Survey, vitamin B12 intake of New Zealand adolescents were shown to be largely adequate, however, changes in dietary patterns over the last 10 years may have negatively impacted the major dietary contributors of vitamin B12 intake. In particular, with global trends emphasizing plant- based diets and the subsequent decline in consumption of milk and animal source foods, it is currently unclear what New Zealand adolescents are eating. As vitamin B12 is naturally found in food of animal origin, young adults that choose to omit animal products are at increased risk of deficiency.
Objective: The aim of the present study was to evaluate dietary vitamin B12 intake, and its major food sources among female and male adolescents aged 15-18 years.
Methods: The present study was part of a larger nutrition assessment project; the Survey of Nutrition Dietary Assessment and Lifestyle (SuNDiAL). SuNDiAL was designed as a clustered, cross-sectional study of 401 female and male adolescents nationwide. Recruitment of participants and data collection took place in 19 secondary schools across ten different regions in New Zealand between February 2019 and April 2020. Eligible participants provided information of their demographic and health status; dietary habits and vegetarian status; and attitudes, motivations and beliefs regarding food choices via online self-administered questionnaires. Anthropometric measurements including height and weight were taken, and BMI (kg/m2) and BMI z- scores were determined. Dietary intake information was collected via two 24-hour recalls on non-consecutive days (the first face-to-face, the second by telephone or video link) within two weeks. Food recall data were entered into a nutrient analysis software programme, FoodWorks 9 to calculate energy and vitamin B12 intake. Energy and dietary vitamin B12 intakes were adjusted for within person variation using the Multiple Source Method to represent usual intakes. Nutrient adequacy was assessed using the EAR cut-point method.
Results: The sample population consisted of 266 females and 135 males self- identifying as New Zealand European or Other (71.2%), Māori (13.7%), Asian (12.7%) and Pacific (2.3%). Only 9% of the sample population reported adopting a vegetarian lifestyle, with a high proportion of vegetarians among female participants compared to males (11% vs 4%, respectively). Usual dietary vitamin B12 intakes were found to be higher in males at 3.8 μg/day compared to that of females at 2.5 μg/day. In addition, inadequate vitamin B12 intake (below <2.0 μg/day) was higher in females (22.6%) than males (10.8%). However, participants who reported following a vegan (n=6) or vegetarian dietary pattern (n=23) showed the highest prevalence of inadequate vitamin B12 intake at 83.3% and 34.8%, respectively. Lastly, the top three major food group contributors of vitamin B12 were foods of animal origin among both females and males; milk, beef and veal, poultry representing 28.3% and 40.5% of total dietary vitamin B12 intake, respectively.
Conclusion: Vitamin B12 intakes in adolescents are largely dependent on consumption of animal products. Majority of participants were achieving their daily recommended requirement (>2.0 μg/day) albeit inadequacy was higher among females and those reporting vegan and vegetarian lifestyles. Consumption of fortified alternatives or supplements may be recommended to attenuate the higher prevalence of inadequate intake among at risk groups.