Vitamin B12 Intakes and Contributing Food Groups of Adolescent Males in New Zealand

Background: Vitamin B12 is an essential co-factor in the one-carbon pathway, with inadequate intake eventually leading to impaired B12 function characterized by megaloblastic anaemia and neurological dysfunction. Adolescent males may be at risk of vitamin B12 deficiency due to increased requirements secondary to growth and poor diet quality. Since the last nationally representative population survey of vitamin B12 intake in 2008/09, there has been a shift across the OECD towards a more plant-based dietary pattern, potentially decreasing the consumption of dietary B12 inherent to flesh foods and dairy products. Ultimately, the current vitamin B12 intake of adolescent New Zealand males is unknown, emphasizing the need for further research in this area. Objective: To assess the usual intake and adequacy of dietary vitamin B12 among adolescent males in New Zealand and determine the major food group contributors of vitamin B12 intake. Design: The present study was part of a larger multi-centre cross-sectional survey of 135 adolescent males aged 15-17 years across New Zealand (Survey of Nutrition, Dietary Assessment and Lifestyles, SuNDiAL). For the purpose of the thesis, usual intakes of vitamin B12 were assessed. Participants were recruited from six secondary schools between February and March 2020. Socio-demographics, dietary habits, supplement use, attitudes and food choice motivation were assessed via an online questionnaire. Anthropometric measurements of height and weight were also collected and used to determine BMI z- score, with classification of participants as normal, overweight and obese. Dietary energy and vitamin B12 intakes were estimated using two 24-hour recalls, adjusted to establish “usual intake” using the Multiple Source Method (MSM), adequacy was determined by comparing usual intake to the estimated average requirement (EAR). The percent contribution of vitamin B12 intake from 33 major food groups were determined and ranked. Results: Of 135 participants who completed enrolment into the study, 102 completed one 24- hr dietary recall and 72 completed the second dietary recall. The usual median (IQR) intake of vitamin B12 was 4.2 (3.9, 4.5) μg/day, with 10% of participants not achieving recommended intakes. The usual median (IQR) vitamin B12 intake appeared higher among older participants (4.6 (2.2) μg/day) and those classified as overweight (4.5 (1.9) μg/day) compared to their respective counterparts. Notably, the greatest prevalence of inadequate intake appeared in participants from the most deprived neighbourhoods (NZdepIndex 8-10), with a prevalence of inadequacy of 25%. Milk was widely consumed by most participants (75%) and as such, was ranked the largest contributor to vitamin B12 intake (21%), followed by poultry (10%), beef and veal (9.5%), fish and seafood (7.6%) and lastly, bread-based dishes (6.7%). Supplement intake was reported by 30% (37 of 122) of participants who completed the dietary habits survey – of which, 35% (13 of 37) reported consuming a B12-containing multivitamin at least once weekly. No single vitamin B12 supplemental intake was reported. Conclusion: Despite world-wide trends toward consuming a diet rich in plant-based foods and fewer animal source foods, adolescent males in the present study had a relatively low risk of vitamin B12 deficiency, however, those from lower socio- economic areas were at moderate risk for suboptimal intakes. Further research in a more representative population of adolescent males is required to confirm the at-risk subgroups identified herein