Vitamin B12 intake, major food sources and the prevalence of inadequacy in New Zealand Adolescent Females

Abstract

Background: Vitamin B12 is an essential water soluble vitamin which is found mostly in animal products. It is essential for DNA synthesis and for the optimal development and functioning of the central nervous system. A deficiency of B12 can cause megaloblastic anaemia and neurological dysfunction. With the increased prevalence of vegetarianism and veganism globally, there is a greater likelihood of inadequate B12 intake as reduced intake of meat and dairy have shown a negative effect on vitamin B12 status. While the prevalence of vegetarianism in New Zealand is unknown, it is assumed to be on the rise with a particular concern as to whether dietary requirements of at risk groups, such as adolescent females, can be met. Objective: To assess the dietary intake of vitamin B12, major food sources and the prevalence of inadequate intakes in a sample of adolescent females in New Zealand. Methods: The present study was the first phase of a larger cross sectional survey of 15-18 year old females across New Zealand. In this first phase, participants were recruited from eight high schools between February and March 2019. Sociodemographic data and dietary habits were collected via an online questionnaire, and anthropometry measurements were taken using standardised procedures. The height and weight recorded from the researchers were used to calculate and categorise the z-BMI score for the participants. Dietary intake, including all food and beverage intake, was measured using two non-consecutive 24-hour diet recalls and estimated energy and vitamin B12 intake were adjusted for intra-individual variation. The contribution of vitamin B12 intake from a total of 33 major food groups were calculated and ranked. Descriptive data were presented using median and interquartile range or mean and 95% confidence intervals where appropriate. Results: Of the 145 participants who were enrolled, 132 participants had completed one 24 hour diet recall. The average age of participants was 16.7 years, the majority identified as New Zealand European and Others (NZEO) (70%) and over one-third were categorised as overweight or obese (34%). The estimated median (IQR) daily intake of vitamin B12 was 2.5 (1.9, 3.3) g, with 30.3% of participants consuming intakes below the Estimated Average Requirement of 2 µg/day. The median energy intake (IQR) was 7833 (6863, 9010) KJ/day. Similar to energy, vitamin B12 intakes of participants attending the highest decile school ranking (10) appeared to be higher compared to other decile rankings. In addition, Pacific participants also appeared to have the highest energy and vitamin B12 intake compared to the other ethnic groups. Beef and veal were the largest dietary contributors of vitamin B12 intake (10%), followed by milk (9.8%) and bread based dishes (8.5%). Of the 124 participants who completed the questionnaire on supplement use, 42 (32%) reported using supplements with seven of these participants taking an oral B12-containing supplement and one participant reported intramuscular B12 every six months. Conclusion: A considerable proportion of adolescent females in this sample population are at risk of vitamin B12 deficiency as over one-third were not achieving recommended dietary intakes of vitamin B12. While further work is needed to achieve a more representative sample population, these findings warrant concern, particularly given the global rise in vegetarianism and further reduction in vitamin B12-rich animal products such as red meat and milk. Dietitians should be aware of the risk of inadequate nutrient intake, including vitamin B12 among adolescent New Zealand females.