Vitamin B12 intake, major food sources and the prevalence of inadequacy

in New Zealand Adolescent Females

Nicholas Hall

A thesis submitted in a partial fulfilment of the requirements for the degree of

Masters of Dietetics

At the University of Otago, Dunedin, New Zealand

June 2019

ii

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

iii

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.

iv

Preface

This project is part of a larger, multi-centre cross-sectional survey called the Survey of

Nutrition, Dietary Assessment, and Lifestyles (SuNDiAL). SuNDiAL is designed to collect

information on food intake, dietary habits, activity level and other lifestyle parameters of

adolescent females in New Zealand and to assess whether any differences exist between

vegetarian and non-vegetarian participants.

This study is the first phase of SuNDiAL recruitment, which in February 2019.

The candidate was responsible for the following:

Delivering an information session to a high school about the study in order to initiate

recruitment

Data collection, including:

- 24-hour recalls

- Anthropometrical measurements

- Accelerometry data (data not used in present study)

- Organisation of blood and urine samples (data not used in present study)

Entry of seven 24-hour diet recalls

Interpretation, presentation and discussion of results

Write up of all thesis components

Dr Jill Haszard, Dr Meredith Peddie (Principal Investigators) and Associate Professor Lisa

Houghton (Co-investigator) were responsible for:

Study design and development

v

Obtaining ethical approval

Recruitment of high schools

Statistical analysis, including adjustment for intra-individual in usual intakes

Supervision of thesis write-up

vi

Acknowledgements

Throughout the writing of this thesis I have received a great deal of support and assistance. I

would first like to thank my supervisor Associate Professor Lisa Houghton for her guidance

throughout each stage of the writing of this thesis.

I would like to thank Dr. Jill Haszard for her organisation of the study design and her

statistical analysis; Meredith Peddie for her role in the organisation of the study design and

school recruitment; Chaya Ranasinghe and Liz Fleming for organising all the data from

FoodWorks and Tessa Scott for your help with organising and recruiting the high schools.

To all of my family and friends, thank you for your support and encouragement throughout

this thesis. I would also like to give a big thank you to my partner, Jess, who helped me with

this thesis and put up with all of the stress involved.

vii

Table of Contents

Abstract ................................................................................................................................. ii

Preface .................................................................................................................................. iv

Acknowledgements ............................................................................................................... vi

List of Tables ........................................................................................................................ ix

List of Figures ........................................................................................................................ x

List of Abbreviations ............................................................................................................ xi

1. Introduction ....................................................................................................................... 1

2. Literature Review ............................................................................................................... 3

2.1 B12 in Food, Absorption and Transport ........................................................................ 3

2.1.1 Chemical structure and properties........................................................................... 3

2.1.2 Food sources and bioavailability ............................ Error! Bookmark not defined.

2.1.3 Absorption, transport and storage ........................................................................... 3

2.1.4 Metabolism and Function ....................................................................................... 4

2.2 Dietary Requirements for B12 ...................................................................................... 7

2.2.1 Nutrient Reference Values ...................................................................................... 7

2.2.2 Consequences of Low Intakes ................................................................................ 8

2.3 Prevalence of Low Intakes in Female Adolescents ...................................................... 10

2.4 Conclusion ................................................................................................................. 13

3. Objective Statement ......................................................................................................... 15

4. Methods ........................................................................................................................... 16

4.1 Study Design .............................................................................................................. 16

4.2 Ethics ......................................................................................................................... 16

4.3 Study setting and participants ..................................................................................... 16

4.4 Online Questionnaire .................................................................................................. 17

4.5 Diet Recalls ................................................................................................................ 18

4.6 Data Entry .................................................................................................................. 19

4.7 Anthropometry ........................................................................................................... 20

4.8 Statistical Analysis ..................................................................................................... 21

5. Results ............................................................................................................................. 22

5.1 Participant Characteristics........................................................................................... 22

5.2 Dietary vitamin B12 intake ......................................................................................... 23

5.3 Major food sources of vitamin B12 ............................................................................. 24

6. Discussion ........................................................................................................................ 27

6.1 Summary of Main Findings ........................................................................................ 27

6.2 Energy and B12 Intake ............................................................................................... 27

viii

6.3 Food Groups ............................................................................................................... 28

6.4 Strengths and Limitations ........................................................................................... 30

6.5 Conclusion ................................................................................................................. 31

7. Application to Dietetic Practice ........................................................................................ 32

8. References ....................................................................................................................... 34

9. Appendices ...................................................................................................................... 45

ix

List of Tables

Table 1. Overview of the nutrient reference values for vitamin B12 for adolescent females

across countries and/or organisations (EFSA, 2015) ............................................................... 8

Table 2. Prevalence of low vitamin B12 intakes in adolescent females from different

populations. ......................................................................................................................... 10

Table 3. Distribution of data collection days. ....................................................................... 21

Table 4. Sociodemographic and anthropometric characteristics of participants who

completed dietary intake and anthropometric measurements (n=132) ................................... 23

Table 5. Dietary intake of energy and vitamin B12 and prevalence of inadequacy of

adolescent New Zealand females (n=132) ............................................................................ 25

Table 6. Major food groups contributing to vitamin B12 intakes .......................................... 26

x

List of Figures

Figure 1. B12 can be found as (1) 5′-Deoxyadenosylcobalamin; (2) methylcobalamin; (3)

hydroxocobalamin; and (4) cyanocobalamin (Watanabe et al., 2007). .................................... 3

Figure 2. B12 dependent methionine synthase (MS) in methionine/ homocysteine/ folate

metabolism (Ma et al., 1999) .................................................................................................. 5

Figure 3. B12 dependent methylmalonyl-CoA Mutase in methylmalonyl-CoA metabolism

(EFSA Journal, 2015) ............................................................................................................ 5

Figure 4. Process of participant recruitment ......................................................................... 18

xi

List of Abbreviations

AFSSA French Food Safety Agency

AR Average Requirement

BMI Body Mass Index

D-A-C-H Germany, Austria and Switzerland

DH UK Department of Health

EAR Estimated Average Requirement

IOM Institute of Medicine

MMA Methylmalonic Acid

MOH New Zealand Ministry of Health

NCM Nordic Council of Ministers

NL Health Council of the Netherlands

NZEO New Zealand European and Other

RDA Recommended Daily Allowance

SCF Scientific Committee for Food

SES Socioeconomic Status

SuNDiAL Survey of Nutrition Dietary Assessment and Lifestyle

THF Tetrahydrofolate

WHO/FAO World Health Organisation, Food and Agriculture Organization

1

1. Introduction

Vitamin B12 is a water soluble vitamin found almost only in animal products and foods

where bacterial fermentation occurs during manufacturing, for example, tempe (Watanabe

et al., 2007, Mo et al, 2013). Vitamin B12 is required for DNA synthesis and therefore the

production of red blood cells (Metz et al., 1968, Ray and Blom, 2003). A deficiency of

vitamin B12 can cause megaloblastic anaemia and a range of neurological symptoms,

from numbness and tingling in the hands and feet, through to confusion, poor memory and

dementia (Healton et al., 1991, Metz et al., 1968). The main causes of vitamin B12

deficiency include poor absorption, pernicious anaemia, gastrointestinal surgery resulting

in malabsorption, and suboptimal dietary intakes.

In New Zealand and Australia, the Estimated Average Requirement (EAR) for 14-18 year

old females is 2.0 µg vitamin B12/day and the Recommended Daily Intake (RDI) is 2.4

µg vitamin B12/day (MOH, 2006). Data have shown a range of inadequate vitamin B12

intakes in adolescent females, from 6% in Europe to 88% in Nepal (Chandyo et al., 2016,

Iglasie et al., 2017). The 2012 Australian Health Survey found 7.7% of 14-18 year olds

were not achieving the EAR for vitamin B12 (ABS, 2015). The most recent national

survey data in New Zealand was collected in 2008/9, where 7.9% of female adolescents

were found to have inadequate intakes (MOH, 2011).

The main dietary contributors of vitamin B12 in the 2008/09 national survey were; milk

(15.5%), bread based dishes (11.9%) and beef and veal (7.9%), with the bread based

dishes including food items such as; burgers, pizza and sandwiches, which contain animal

products.

Currently there are limited data in New Zealand on the prevalence of people identifying as

vegetarians or vegans however, the United Kingdom has seen the rate of vegetarianism

2

increase since the 1960’s. This trend suggests New Zealand may be experiencing a similar

shift in the rate of vegetarianism (Leahy et al., 2011).

. In this case, vitamin B12-rich food sources may be consumed less frequently and New

Zealanders may have an increased risk for vitamin B12 deficiency. This is a particular

concern for lifecycle groups who are experiencing growth and development such as

infants, children and adolescents. For this study, adolescent females have been chosen as

the target group due to their ongoing growth and higher requirement needs, reproductive

age and increased likelihood to reduce their consumption of meat (Roy Morgan, 2016)

Therefore, this study aimed to describe the prevalence of inadequate vitamin B12 intake

among adolescent females in New Zealand. It also aimed to describe the major dietary

contributors of vitamin B12 in New Zealand adolescent females. The results will

contribute to a better understanding of whether B12 intakes have changed over the last ten

years and will aid in the development of national guidelines tailored to this population

group.

3

2. Literature Review

2.1 B12 in Food, Absorption and Transport

2.1.1 Chemical structure and properties

Vitamin B12 (cobalamin) has a central cobalt atom which is surrounded by a planar corrin

ring structure, with four pyrrole nitrogen’s coordinated to the cobalt. Vitamin B12 refers to a

group of biologically active cobalamins. The upper axial position can be one of; cyano,

methyl, hydroxyl, and 5′-deoxyadenosyl groups (Figure 1) (Shane, 2008). Vitamin B12 is the

largest and most complex vitamin and is only synthesised by certain bacteria and archaea

(Watanabe and Bito, 2018). The water soluble vitamin has a molecular weight of 1355.4

(Watanabe et al., 2007) and a deep red colour (Rossi, 1985).

Figure 1. B12 can be found as (1) 5′-Deoxyadenosylcobalamin; (2) methylcobalamin; (3)

hydroxocobalamin; and (4) cyanocobalamin (Watanabe et al., 2007).

2.1.3 Absorption, transport and storage

In the upper gastrointestinal tract, B12 is released from food and bound to a protein,

haptocorrin, which is present in saliva and gastric fluids. This prevents the hydrolysis of B12

whilst in the acidic stomach environment (Savage and Green, 1976; Gordon et al., 1991).

Haptocorrin is then degraded by pancreatic enzymes in the duodenum which allows for B12

to bind to intrinsic factor (IF) – a protein secreted by the parietal cells of the mucosa of the

gastric wall (Gordon et al., 1991). Intrinsic factor-bound vitamin B12 is absorbed primarily in

the terminal ileum (Donaldson et al., 1967) by a receptor complex called cubam (Fyfe et al.,

2004). Cubam facilitates the absorption of the IF-B12 complex but will not work for either

4

component on their own (Birn et al., 1997). When given large quantities of B12, passive

diffusion can occur without the aid of IF (Reisner et al., 1955). Inside the ileal enterocyte,

intrinsic factor is degraded and B12 is released (Pedersen et al., 2010). Vitamin B12 can then

either stay inside the cell to be used as a coenzyme or for storage, or it can exit the cell via

multidrug resistance protein 1 (MRP1) (Beedholm-Ebsen et al., 2009). Upon MRP1-mediated

exit into the bloodstream, B12 binds to transcobalamin for transportation. Transcobalamin

(TC) is a B12 binding protein which transports B12 to other tissue and cells (Namour et al.,

2003). The TC-B12 complex is taken up by the cells and then the transcobalamin is degraded

into amino acids by lysosomes and the B12 is left in the cytoplasm (Youngdahl-Turner et al.,

1978).

The average cobalamin content of the body was estimated to be 2–3 mg in healthy

adults (Adams, 1970; Reizenstein et al., 1966). Approximately 1 μg per gram of liver tissue

wet weight is B12 which accounts for about 50% of the total body stores (Stahlberg et al.,

1967). Due to the high activity of vitamin B12 in the kidneys, Gräsbeck (1961) has proposed

they may have a storage function.

Vitamin B12 is transported to tissues and cells via TC. Cells express specific

receptors, which internalize the vitamin as the TC-cobalamin complex (Rothenberg &

Quadros, 1995). Upon its entry into the cell, the TC is degraded, the cobalamin is released and

converted to the co-enzyme forms, adenosylcobalamin and methylcobalamin, which serve as

cofactors for two cobalamin dependent enzymes (Quadros et al., 1976; Chanarin, 1979).

2.1.4 Metabolism and Function

In humans, two reactions are known to require B12 as coenzyme; the conversion of

methylmalonyl-CoA to succinyl-CoA by methylmalonyl-CoA mutase in the mitochondria and

transmethylation of homocysteine by 5-methyltetrahydrofolate (5-methylTHF) to methionine

by methionine synthase which also forms tetrahydrofolate (THF).

5

B12 dependent methionine synthase (MS) converts homocysteine to methionine

(Figure 2). Methylcobalamin acts as the methyl carrier between 5-methylTHF and

homocysteine which results in methionine and THF (Ma et al., 1999).

Figure 2. B12 dependent methionine synthase (MS) in methionine/ homocysteine/ folate

metabolism (Ma et al., 1999)

Adenosylcobalamin functions as a coenzyme for methylmalonyl- CoA mutase, which

catalyses the conversion of methylmalonyl-CoA to succinyl-CoA which is used in the

tricarboxylic acid cycle (Figure 3) (Ludwig and Matthews, 1997).

Figure 3.B12 dependent methylmalonyl-CoA Mutase in methylmalonyl-CoA metabolism

(EFSA Journal, 2015)

6

2.1.2 Food sources and bioavailability

In the 2008/9 New Zealand Adult Survey, the primary food source of B12 amongst New

Zealand females between the ages 15-18 years was milk (15.5%), followed by bread based

dishes, such as sandwiches (11.9%), beef and veal (7.9%) and chicken eggs (3.9%) (New

Zealand Ministry of Health, 2011).

The amount of B12 in cow’s milk can vary depending on the breed, seasonal variation

and breeding state. The Holstein-Friesian cow, the most common dairy cow breed in New

Zealand (Harris and Kolver, 2001), produces milk which contains 0.44 µg of vitamin B12 per

100 ml (Rutten et al., 2013). Ruminant animals are herbivores and therefore do not consume

any B12 in their diets. They must rely on the B12-synthesizing bacteria that dwell within their

four stomachs to provide them with ample B12. As a result, the level of B12 in meat and milk

from ruminant animals is higher than other animals (Ortigues-Marty et al., 2005; Watanabe

and Bito, 2018).

Plant-based foods contain little to nil amounts of B12, however the use of organic

fertilisers can increase the B12 content of certain vegetables. A review by Mozafar (1994)

found that using organic fertilisers or spraying B12 onto plants such as spinach could increase

the amount of B12 found within the plants. However the B12 levels were only able to be

raised to approximately 0.14 µg/100 g fresh weight, which may not significantly contribute to

the average person’s B12 intake. Tempe, a fermented soybean product which is traditional in

Indonesia, contains B12 due to the microbial growth which occurs during the fermentation

process (Mo et al., 2013). The B12 content of tempe can substantially vary, ranging from 0.08

µg/100g (Sivakumaran et al., 2017) to 8 µg/100g (Nakos et al., 2016). Other foods such as

spirulina, an edible cyanobacterium sold as a supplement in health food stores (Belay et al,

1993), contain high amounts of pseudo B12 – a corrinoid which is structurally similar to other

B12 molecules, yet shown to have a very low affinity for the human intrinsic factor which

reduces the bioavailability (Stupperich and Nexo, 1991).

7

In people with normally functioning gastric systems, naturally occurring B12 is

assumed to have a 50% bioavailability (Heyssel et al., 1966). Chicken, mutton, and liver have

a bioavailability of 60%, 65%, and 9%, respectively. The bioavailability of liver is low due to

the high concentration of B12, resulting in a saturation of the intrinsic factor (Heyssel et al.,

1966). Some fish such as trout have a bioavailability of 25%–47% (Doscherholmen et al.,

1983) while the bioavailability of cooked eggs ranges from 24-36% (Doscherholmen et al.,

1978).

2.2 Dietary Requirements for B12

2.2.1 Nutrient Reference Values

In New Zealand and Australia, the EAR for 14-18 year old females is 2.0 µg vitamin B12/day

and the RDI is 2.4 µg vitamin B12/day (MOH, 2006). The EAR was based on the amount of

intramuscular cobalamin required daily to maintain haematological status and serum

cobalamin concentration in seven patients with pernicious anaemia in remission. An average

physiological requirement of cobalamin was set at 0.7 μg vitamin B12/day (Darby et al.,

1958); however, the need for additional work has been raised due to the small sample size of

this study. After adjusting for the additional cobalamin losses in faeces in these patients

compared with healthy individuals (0.5 μg vitamin B12/day) (El Kholty et al.,1991), and

assuming an average bioavailability of 50% from evidence on radioactive cobalamins (Adams

et al., 1971) the EAR was set at 2 μg vitamin B12/day. After assuming a coefficient of

variation of 10%, the RDI of 2.4 μg/day was established. The adult EAR for vitamin B12 was

then extrapolated using allometric scaling to set the RDI for children. In adolescent females,

the RDI for vitamin B12 remains the same as that for adults (EFSA, 2015). Table 1 provides

an overview of the different nutrient reference values of vitamin B12 in different countries.

8

Table 1. Overview of the nutrient reference values for vitamin B12 for adolescent females

across countries and/or organisations (EFSA, 2015)

D-A-C-

H

(2015)

NCM

(2014)

WHO/FAO

(2004)

NL

(2003)

Afssa

(2001)

IOM

(1998)

SCF

(1993)

DH

(1991)

Age

(Years)

13-<19 10-17 10-18 14-18 16-19 14-18 15-17 15-18

EAR/

AR

(μg/day)

2.0 1.4 2.0 2.0 2.0 2.0 1.0 1.25

Abbreviations: D-A-C-H, Germany, Austria and Switzerland; NCM, Nordic Council of

Ministers; WHO/FAO, World Health Organisation, Food and Agriculture Organization; NL,

Health Council of the Netherlands; Afssa, French Food Safety Agency; IOM, Institute of

Medicine; SCF, Scientific Committee for Food; DH, UK Department of Health; AR, Average

Requirements.

Intakes of 4-7 μg vitamin B12/day show improvements for holotranscobalamin,

methylmalonic acid (MMA), serum B12 and homocysteine levels compared to the current

RDA of 2 μg vitamin/day (Pentieva et al., 2012; Bor et al., 2010). In contrast, the longer term

effects of high B12 intakes are unknown with a lack of dose-response data to support setting

an upper level for B12 (MOH, 2006). The lack of toxicity has been thought to be due to the

body’s ability to reduce absorption when exposed to high amounts of B12.

2.2.2 Consequences of Low Intakes

The most commonly used indicators to measure B12 status are; methylmalonic acid

(MMA), serum B12, homocysteine and holotranscobalamin. Low serum vitamin B12 is not

closely correlated with clinically relevant symptoms so is generally not considered a useful

indicator of B12 status (Cooper et al., 1986). MMA is a sensitive metabolic marker for

vitamin B12 deficiency (Herman er al., 2003). Holotranscobalamin has been shown to

9

correlate with B12 status well at high levels but exhibits poor correlation at lower levels

(Herman et al., 2003). Vitamin B12 dependent methionine synthase is used to convert

homocysteine to methionine, therefore, homocysteine can be used as an indicator for B12

deficiency as it is raised in people who are B12 deficient. However, this biomarker is non-

specific as homocysteine is also raised when there is a folate deficiency (Stabler et al, 1988).

When compared against each other, holotranscobalamin was found to have performed the best

in an elderly population (Valente et al., 2011). Serum B12 is routinely used due to the cost of

the other markers.

B12 plays an important role in developing and maintaining the central nervous system

(Ray and Blom, 2003). B12 deficiency can result in a number of neurological symptoms such

as; paraesthesia, gait ataxia, memory loss, orthostatic light headedness, anosmia, paranoid

psychosis and reduction of vision (Healton et al., 1991). A lack of B12 can also result in

megaloblastic anaemia due to the interruption of DNA synthesis (Metz et al., 1968).

Megaloblastic anaemia, neurological symptoms, vibratory loss, proprioceptive loss and other

symptoms have been caused by a B12 deficiency (Savage et al., 1994).

In the elderly, a prospective study found that low B12 status was associated with

higher rates of cerebral atrophy, which has been associated with Alzheimer’s disease

(Vogiatzoglou et al., 2008). Moreover, B12 deficient elderly people have been shown to be

more likely to have a depressive disorder (Tiemeier et al., 2002). Nonetheless, B12

supplementation has not been found to improve cognitive function in the elderly (Doets et al.,

2013).

Reproductive age women including adolescent females need to ensure optimal B12

status as it is associated with the status of the offspring (Honzik et al., 2009). Moreover, a low

B12 intake for an infant can lead to myelination retardation, cerebral atrophy, anaemia,

hypotonia and failure to thrive (Lovblad et al., 1997; Honzik et al., 2009). Furthermore, a low

10

maternal serum B12 status has been associated with higher rates of neural tube defects in

offspring (Molloy et al., 2009).

2.3 Prevalence of Low Intakes in Female Adolescents

The intakes of B12 tend to be the highest in high socioeconomic status (SES), urban

populations with low rates of vegetarianism. Different studies have used either serum B12 or

the AR/ EAR to determine an inadequate B12 intake. The prevalence of low vitamin B12

statuses are shown in Table 2.

Table 2. Prevalence of low vitamin B12 intakes in adolescent females from different

populations.

Prevalence of

Low Intake

(Indicator)

Location Median Intake

(μg /day)

Age Range

in Years

Reference

6.0% (Dietary

Intake)

10 European

Cities from 9

countries

4.2 12.5-17.5 Iglasie et al., (2017)

7.4% (Serum

B12)

India -1

12-18 Gupta et al., (2016)

7.7% (Dietary

Intake)

Australia 3.5 14-18 Australian Bureau of

Statistics (ABS),

(2015)

7.9% (Dietary

Intake)

New Zealand 3.4 15-18 Ministry of Health:

A Focus on

Nutrition, 2008/9

9.2% (Serum

B12)

Nigeria -1

12-16 VanderJagt, et al.,

(2000)

15.8% deficient.

33.8% marginal.

(Serum B12)

Belize -1

15-24 Rosenthal et al.,

(2017)

19.5 +/- 12.5 %

(Dietary Intake)

Mexico 3.27 12-18 Pedroza-Tobias et

al., (2016)

31.0% (Serum

B12)

India -1

11-17 Chakraborty et al.,

(2018)

35.6% (Dietary

Intake)

Costa Rica -1

10-16 Monge-Rojas et al.,

(2005)

11

36.99% (Serum

B12)

Venezuela -1

15 Garcia-Casal et al.,

(2005)

88% (Dietary

Intake)

Nepal 0.25 13-20 Chandyo et al.,

(2016)

-1

Cameroon 0.9 12-16 Dapi et al., (2011)

1Data unavailable

In Cameroon, SES is an important indicator for B12 intake with the mean B12 intake

of low SES groups 0.6 vs 1.5 μg/day for the high SES group (). Amongst adolescents, meat

and milk products are consumed more frequently in urban areas compared to rural areas in

Cameroon (Dapi et al., 2010). There is generally poor food variety for adolescents in

Cameroon andeven in the high SES group, meat and dairy intake is still relatively low which

is a likely cause of the low mean daily B12 intake. Although inadequate intake was not

calculated, it appears that most of the adolescent females were consuming less B12 than the

EAR (Dapi et al., 2011). No true comparisons can be made as only one school was selected to

represent a socioeconomic level.

The low B12 intake in Nepal may be due to a low meat, fish and dairy consumption.

From the 775 24-hour dietary recalls, more than half of the study population reported that

they had only consumed any meat 1–3 times a month or less during the past six months.

Buffalo meat accounted for 58% of the B12 intake whilst only being present in 18% of the

recalls (Chandyo et al., 2016). This study is not representative of Nepal and only included

local residents or carpet factory workers from a Municipality within the Kathmandu Valley.

Since Venezuela experienced an economic crisis in 1985, life conditions have

worsened. From 1994-1998, the cost of a basic diet for a family of five, increased nearly 30

fold. As a result, many people from different socioeconomic status groups were unable to

achieve their nutritional requirements and there has been a progressive reduction in the quality

and quantity of food consumption (Garcia-Casal et al., 2005). There is no information on food

consumption or the sources of vitamin B12 in the study.

12

In Costa Rica, a small survey found that Cabécar adolescent females have a high

proportion of inadequate B12 intake. This is thought to be due to their vegetable rich and low

energy diet, poverty and neglect (Monge-Rojas et al., 2005). This was performed on a small

sample of females (n=49) and may not be representative of the area.

A boarding school in Nigeria was found to provide low amounts of animal products,

despite this, the participants had a low prevalence of inadequate B12 intake compared to other

countries (VanderJagt et al., 2000). Only information on typical school meals was provided

which does not provide adequate information on what the participants were consuming.

In Belize, there was a high rate of B12 deficiency amongst 15-24 year old females

which was even higher in the 25-34 and 35-49 year age brackets (Rosenthal et al., 2017). This

study examines the age group of 15-24 year olds which may be too large of an age range for a

good comparison.

In India, the rate of B12 deficiency varies drastically between two studies. A lower

rate of B12 deficiency was found in a population where there are few vegetarians, compared

to a larger population where the number of strict vegetarians was higher (Gupta et al., 2016).

The study was not representative for the whole of India. A higher prevalence of vegetarianism

resulting in the low consumption of B12 is blamed for the high rates of B12 deficiency in

India. An inverse relationship between obesity and B12 status was also established. The

authors suggested that cereal fortification may be useful to reduce this prevalence. There was

also a higher rate of deficiency in the rural population where the socio-economic status is

lower (Chakraborty et al., 2018). This study included participants from 11-17 years old which

may affect the results as 11 year olds may have different dietary patterns to 17 year olds.

In Mexico, there is a higher prevalence of inadequate intake of B12 in the rural areas

and in low socio-economic status families (Pedroza-Tobias et al., 2016). In this study, a large

random subsample of people were interviewed which was representative at the national,

regional, state and urban-rural level. Similar to the study in India, Pedroza-Tobias et al.,

13

(2016) analysed the adolescent group as 12-19 year olds, which could provide similar

limitations.

The 2012 Australian Health Survey is a nationally representative survey which

included nutritional information from two 24-hour diet recalls on 12,153 participants. The

recalls were performed at least 8 days apart and were performed via the automated multiple

pass method. Milk products and dishes were consumed by 85% of the participants as well as

meat, poultry and game products and dishes were consumed by 69%.The low rate of vitamin

B12 inadequate intakes may be a result of the high prevalence of milk and meat consumption

(ABS, 2015).

A low prevalence of inadequate B12 intake was reported in Europe where there was a

high consumption of meat, fish and dairy products (Iglasie et al., 2017). Despite this, there

was still an association made between socio-economic factors and the serum B12 status of

adolescent females in Europe (Iglasie et al., 2014).

In 2008/09 New Zealand had a relatively low prevalence of inadequate B12 intake for

adolescent females as compared to other countries. There appears to be a pattern from the

above literature that adolescent females who live in rural areas with a low SES and have low

meat and seafood intakes are the most at risk of having an inadequate B12 intake. With plant

based diets becoming more popular and the SES gap widening in New Zealand (Oranga et al.,

2011), the prevalence for inadequate B12 intakes may be different to the 2008/09 data we

have.

2.4 Conclusion

Vitamin B12 is a complex structure which is only synthesised by bacteria. It is found almost

exclusively in animal products, especially ruminant animal, food sources. In 2008/9, milk

was the main source of vitamin B12 for adolescent females in New Zealand.

14

Vitamin B12 must bind to the intrinsic factor which is released from the parietal cells

in the stomach to be absorbed by the distal end of the ileum. Therefore, B12 must be acquired

through consuming animal products, oral supplements or through injection.

As humans, we require B12 as it acts as a co-enzyme for two reactions. The EAR for

14-18 year old females is 2.0 µg vitamin B12/day and the RDI is 2.4 µg vitamin B12/day. The

main complication B12 deficiency can cause is megaloblastic anaemia, which results due to

the interruption of DNA synthesis.

Around the world, B12 deficiency in female adolescents ranges from 6-88%. A low

intake of meat and dairy is related to a higher rate of B12 deficiency. It is very important for

females of child bearing age to have an adequate B12 status as a poor status can have health

consequences for their children.

In New Zealand, the last data for adolescent B12 status was collected in 2008/9. Since

2009, meat and dairy alternative products seem far more prolific globally, it is likely dietary

patterns have changed (Food Frontier, 2019). If the major sources of B12 in the New Zealand

diet have been replaced in some groups, there may be a concern for their B12 status.

Therefore the current B12 status of adolescent females could be very different from this 10

year old data and deserves further investigation.

15

3. Objective Statement

Despite the clear effect vitamin B12 status has on growth, development, anaemia and

gestational health of adolescent females, their status has not been measured in New Zealand

since 2008/9. There appears to have been a rise in the rate of vegetarian/ vegans in New

Zealand with the apparent emergence of vegetarian/ vegan options in supermarkets and

restaurants which could affect the status of vitamin B12 in New Zealand. Therefore, the aim

of this study is to describe the prevalence of inadequate vitamin B12 intake and the major

sources of vitamin B12 in adolescent females in New Zealand.

16

4. Methods

4.1 Study Design

This study is part of a larger, cross-sectional survey called the Survey of Nutrition, Dietary

Assessment, and Lifestyles (SuNDiAL) designed to collect information on food intake,

dietary habits, activity level and other lifestyle parameters of adolescent females in New

Zealand. The overall aim of the study is to assess whether any differences exist between

vegetarian and non-vegetarian adolescent females. The study began in February 2019 with

phased recruitment periods. This thesis focuses on the vitamin B12 intakes of participants in

the first recruitment period which took place between February and March 2019.

4.2 Ethics

The study was approved by the University of Otago Human Ethics Committee (Health):

H19/004 and is registered with the Australian New Zealand Clinical Trials Registry:

ACTRN12619000290190 (Appendix A). All participants provided informed consent online.

In addition, parental written informed consent was obtained from participants less than 16

years of age.

4.3 Study setting and participants

Participants were recruited from the following high schools across New Zealand;

Tauraroa Area School (Whangarei), Mt Maunganui College (Tauranga), Spotswood College

(New Plymouth), St Catherine's College (Wellington), Waimea College (Nelson),

Hornby High School (Christchurch), Columba College (Dunedin), and Kaikorai Valley

College (Dunedin). High schools were selected based on their location (to accommodate the

Master of Dietetic students collecting the data), decile, and female roll number. A school

decile ranking is measured by the extent to which the school’s students live in a low socio-

economic area with a lower rating indicating a lower socio-economic area. However the

ranking does not indicate the mix of socio-economic status in the school (MOE, 2020). Out

17

of 97 eligible schools, 25 were selected and contacted by email in November 2018. Follow-up

emails and phone call were made to schools that did not reply within two weeks. Three

schools declined to take part in the study, two schools accepted but were unable to be

contacted for any further action and 15 schools did not reply to either email or the phone call.

As a result, three additional schools were invited.

Information sessions were held at the participating schools to explain the aim of the

study and data collection procedures. Eligible participants had to be; female, between 15 and

18 years of age, enrolled in one of the recruited high schools, and able to speak and

understand English to complete the required online questionnaires. Those who self-identified

as female were eligible. Participants were excluded from the study if they knew they were

pregnant. Figure 4 depicts participant recruitment. Participants were provided an information

and consent form in order to check eligibility (Appendix B).

4.4 Online Questionnaire

Participants were administered an online questionnaire which included questions on; age,

ethnicity and frequency of: meat, dairy, egg, energy drink, meat alternative, fast food and

supplement(s) intake (Appendix C). With regards to supplement use, the participants were

asked if they had taken any supplements in the last year, what type of supplements they had

used, and for those who had taken a multivitamin or multimineral, how long they had taken

the supplement for in the last 12 months. The participants were also asked to write the brand

and product name of the multivitamin or multimineral and provide a photo of the

supplement(s) they were taking. The same questions were asked for the use of single vitamin

or mineral supplements.

18

• 59/182 16-18 year olds did not respond

• 13/81 parents of 15 year olds did not respond

• 38/68 15 year olds did not respond after parental consent

• (3 responded to link but declined)

• (9/18 parents of 16-18 year olds from one school that required parental consent did not respond or were uncontactable)

1882 eligible participants

• ~806 present at recruitment drives

153 consented to participate

144 completed enrolment

• 144 completed the health & demographics questionnaire

• 129 completed the attitudes and motivations questionnaire

• 124 completed the dietary habits questionnaire

124 completed a 24hr recall

• 107 completed repeat 24 hr recalls

• 17 refused repeat

263 eligible participants sent link to enrolment

Figure 4. Process of participant recruitment

4.5 Diet Recalls

Dietary intake was measured using two non-consecutive 24-hour diet recalls collected by

trained MDIET students. The first recall was obtained through a face-to-face interview, and

the second recall was obtained either via phone call, video call or school visit within 14 days

19

of the first record. Preference was placed on the second recall being performed on a weekend

day.

The 24-hour recall procedure was conducted in three-stages beginning with a quick list

whereby the participant was asked to list everything they had consumed over the entire 24-

hour period of the day before the recall (midnight to midnight). To improve recollection, the

participant was encouraged to think about what they were doing or who they were with

throughout the day. Next, participants were asked to recall the portion size, brand, flavour,

cooking method and consumption time of each item. Participants were also asked whether

they had added anything, such as sauces, to each meal and/or food item. The participant was

asked if there were any leftovers or if they had a second helping. Visual aids were used to

help estimate portion sizes. The visual aids consisted of; a photo book which contained

images of food models and their weights, dried beans, crockery, measuring cups and different

sized wooden spheres. The second list was then read back to the participant and they were

asked if there was anything they had forgotten to recall. Recipes were recorded on a separate

sheet so all the ingredients and cooking method could be accounted for, including adjustments

in nutrient and moisture losses during cooking.

4.6 Data Entry

All food and beverage intake data were entered into FoodWorks (version 9.0.3973 developed

by Xyris Software Pty Ltd, Australia). This software uses the New Zealand Food

Composition Table (New Zealand FOODfiles™ 2016 Version 01). A code book (Code Book

SuNDiAL 2019 S1- Default Foods and Food Substitutions) was used to assist with data entry

in cases where the MDIET student was unable to obtain sufficient information about a food

item or if it was not in the FoodWorks database. The code book provided food substitutions

and weight estimations used in previous nutrition studies (BLISS and SWIFT). Where no

adequate substitutions could be made to an item not in the FoodWorks database or in the code

book, a recipe which closely resembled the item was developed. Similarly, for packaged food,

20

recipes were also developed with the aim of obtaining a similar composition to the ingredients

and nutrition label found on the package. To ensure the quantities of the ingredients were

correct, the macronutrients in the recipe were compared to that of the packaged food. Total

energy, carbohydrate, fibre, fat, protein and sugar of the recipe were to be within a 10% range

of the nutritional label. After entering the diet records into FoodWorks, the diet record sheets

were cross checked by a PHD candidate to ensure there were no errors.

Dietary intake of vitamin B12 was determined from the two 24-hour recalls and adjusted for

usual intakes using the Multiple Source Method to correct for foods which are rarely eaten in

order to improve estimates of usual intake (Harttig, et al, 2011). The EAR cut-point method

was then applied to estimate the prevalence of inadequate vitamin B12 intake

(Carriquiry,1999).

4.7 Anthropometry

Participant height and weight was measured by trained MDIET students using standardized

procedures. The height was taken using a calibrated portable stadiometer (Seca 213,

Germany). Participants were asked to remove their shoes as well as any hair ornaments or

buns/braids on the top of the head; and the participant’s head was aligned in the Frankfort

horizontal plane. Duplicate measurements were recorded to the nearest 0.1 cm. If height

measurements were not within 0.5 cm, then a third measurement was taken. For weight, the

participant was first asked to remove any heavy clothing (such as jackets, heavy tops and

boots) and duplicate measurements were recorded to the nearest 0.1 kg using an electronic

scale (Medisana-PS 420, Salter- 9037 BK3R, Seca- Alpha 770, Soehnle- Style Sense Comfort

400). A third measurement was taken if the two measurements were not within 0.5 kg. The

BMI classification was calculated by using the WHO BMI-for-age girls growth chart (WHO,

2007).

21

4.8 Statistical Analysis

The overall sample size calculated for the SuNDiAL project was 300 participants from 14

high schools. This gives 80% power to the α=0.05 level to detect a 0.5 standard deviation

difference in continuous outcome variables between vegetarians and non-vegetarians,

assuming the sample includes 20% vegetarians, and a design effect of 1.5. Descriptive results

were performed using Excel (version 14.0.7232.5000, Microsoft, USA). Entered food items

were assigned to a group based on the Food groups used in the 2008/09 New Zealand Adult

Nutrition Survey (MOH, 2011) (Appendix D). Total amounts of vitamin B12 intake from

each of the 33 food groups were calculated for each participant. The proportion of their

total vitamin B12 intake from each of the 33 food groups was calculated. The mean and 95%

confidence intervals of these proportions were then calculated for the whole group using

Stata 15.1 (StataCorp, Texas). Table 3. presents the proportion of 24-hour diet recalls on each

day.

Table 3. Distribution of data collection days.

Day of the week First 24 h Recall (%) Second 24 h Recall (%)

Monday 9.85 22.12

Tuesday 12.88 8.85

Wednesday 34.85 6.19

Thursday 29.55 5.31

Friday 12.12 13.27

Saturday 0 22.12

Sunday 0.78 22.12

22

5. Results

5.1 Participant Characteristics

In total, 144 participants were recruited from eight high schools. School deciles ranged from

three to ten, with the majority of schools rating between five to six. Four of the eight schools

were from the North Island. Sociodemographic characteristics of 132 participants who had

complete dietary intake are presented in Table 4. The average age of participants was 16.7

years and the majority identified as New Zealand European and Others (NZEO). Over one-

third (34%) of participants were categorised as overweight or obese. Of the 124 participants

who completed the questionnaire on supplement use, one-third reported using supplements

with seven of these participants taking an oral B12-containing supplement and one participant

reported intramuscular B12 every six months.

23

Table 4. Sociodemographic and anthropometric characteristics of participants who

completed dietary intake and anthropometric measurements (n=132)

Abbreviations: NZEO, New Zealand European and Others

1 n=131

2 n=130

3n=124

5.2 Dietary vitamin B12 intake

Table 5 presents the usual intake of energy and vitamin B12 by sociodemographic and BMI

classification groups. Overall, energy intakes appear to be higher in Pacific participants

compared to NZEO, Asian and Maori and higher in participants attending the highest decile

school ranking compared to the lower decile rankings. It should be noted that sample sizes are

smaller for both Pacific (n=5) and Asian (n=6) participants as well as those attending decile

10 schools (n=15) and thus, caution is warranted when interpreting the apparent differences.

Characteristic n (%)

Age, years [mean (SD)] 16.7 (0.9)

Ethnicity1

NZEO 92 (70)

Maori 28 (22)

Asian 6 (5)

Pacific 5 (4)

School deciles [median (IQR)] 6 (5, 8)

1-2 0 (0)

3-4 14 (11)

5-6 59 (45)

7-8 44 (33)

9-10 15 (11)

Body mass index (BMI) classification2

Thin 4 (3)

Normal 81 (61)

Overweight 33 (25)

Obese 12 (9)

Any supplementation use3

42 (32)

Supplement-containing B12 7 (6)

24

The estimated median (IQR) daily intake of vitamin B12 was 2.5 (1.9, 3.3) g, with nearly

one-third of participants consuming intakes below the EAR of 2 µg/day. Usual daily intakes

or prevalence of inadequacy did not appear to differ between age groups but do appear to be

higher in Pacific participants compared to NZEO, Asian and Maori participants. Similar to

energy, vitamin B12 intakes of participants attending the highest decile school ranking (10)

appear to be higher compared to other decile rankings. Overweight and obese participants also

appear to have a higher proportion of usual intakes which do not meet the EAR compared to

the normal weight participants.

5.3 Major food sources of vitamin B12

Beef and veal was ranked the top contributor of vitamin B12 intake, however, only 27% (35

of 131) of participants consumed this food (Table 6). In contrast, 60% (79 of 131) of

participants consumed milk – the second highest ranked food group contributor to vitamin

B12 intakes. Overall, the top ten food groups accounted for nearly three-quarters of the

vitamin B12 intake of the sample population, with the majority of these food groups being

animal-source foods. It should be noted that the bread based dishes included items such as

sandwiches, pizza and burgers – all containing animal-source products. Likewise, grains and

pasta included meat lasagne, sushi and macaroni and cheese, and sauces and condiments were

either cheese-based sauces, mayonnaise or yeast extracts such as Marmite.

25

Table 5. Dietary intake of energy and vitamin B12 and prevalence of inadequacy of

adolescent New Zealand females (n=132)

Characteristic n

Energy (KJ) Vitamin B12 (g/d) Prevalence

of

inadequacy

n (%) Median (IQR)

Median

(IQR)

Mean

(SD)

All 132 7833 (6863, 9010) 2.5 (1.9,

3.3)

2.7 (1.27) 40 (30.3)

Age, years

15-16 74 8057 (6830, 9246) 2.6 (1.9,

3.5) 2.9 (1.44) 22 (29.7)

17-18 58 7660 (6870, 8848) 2.4 (1.8,

3.1) 2.6 (1.00) 18 (31.0)

Ethnicity

NZEO 92 7943 (6863, 9085) 2.5 (2.0,

3.3) 2.7 (1.03) 24 (26.1)

Maori 28 7511 (6995, 8232) 2.1 (1.6,

3.2) 2.8 (1.87) 12 (42.9)

Asian 6 6709 (6221, 8248) 2.1 (1.9,

2.5) 2.6 (1.30) 3 (50.0)

Pacific 5 9166 (9012, 12153) 3.9 (3.1,

4.2) 3.7 (1.17) 0 (0.0)

School Decile

10 15 8952 (7812, 9638) 3.2 (2.2,

3.8) 3.1 (1.27) 2 (13.3)

8 28 8287 (6918, 9502) 2.7 (2.2,

3.2) 2.8 (1.07) 5 (17.8)

7 89 7580 (6786, 8695) 2.4 (1.7,

3.3) 2.6 (1.32) 33 (37.1)

6 34 7806 (6999, 9087) 2.7 (2.0,

3.3) 2.7 (1.04) 9 (26.5)

5 25 7364 (6488, 8287) 2.1 (1.6,

2.6) 2.3 (1.00) 12 (48.0)

3 14 7526 (6745, 8837) 2.6 (1.6,

2.9) 2.9 (2.24) 5 (35.7)

BMI Classification

Thin 4 7364 (6446, 8532) 2.2 (2.1,

2.5) 2.3 (0.40) 0 (0.0)

Normal 81 7941 (6867, 9166) 2.8 (2.0,

3.5) 2.8 (1.11) 21 (25.9)

Overweight 33 7715 (6880, 8536) 2.3 (1.7,

2.9) 2.6 (1.55) 12 (36.4)

Obese 12 7792 (6442, 9136) 2.2 (1.5,

4.4) 2.8 (1.52) 6 (50.0)

Overweight

and obese 45 7715 (6816, 8695)

2.3 (1.7,

3.1) 2.6 (1.53) 18 (40)

Abbreviations: NZEO, New Zealand European and Others; BMI, Body Mass Index

26

Table 6. Major food groups contributing to vitamin B12 intakes

Food groups

Contribution to vitamin

B12 intake of population

No. of participants who

consumed food group

Mean (95% CI), % n (%)

Beef and Veal 10.0 (6.7, 13.3) 35 (27)

Milk1

9.8 (7.4, 12.1) 79 (60)

Bread based dishes2

8.5 (5.6, 11.3) 42 (32)

Poultry 7.80 (9.6, 10.0) 71(54)

Egg and egg dishes 7.3 (4.7, 10.0) 36 (27)

Grains and pasta 6.5 (4.0, 9.0) 41(31)

Fish and seafood 6.2 (3.0, 9.3) -3

Cheese 6.0 (4.2, 7.9) 60 (45)

Savoury sauces and

condiments 5.2 (2.5, 7.9) -

3

Sausages and

processed meats 4.6 (2.7, 6.4) -

3

1Includes all types of milk

2Includes bread rolls and specialty breads

3 Data unavailable

27

6. Discussion

6.1 Summary of Main Findings

The present study describes the prevalence of inadequate vitamin B12 intake and the major

sources of vitamin B12 in adolescent females in New Zealand. Almost one-third of

participants did not achieve the EAR of 2 µg vitamin B12/day. Participants who were

overweight and obese appeared more likely to have inadequate B12 intakes than normal

weight and thin participants. In contrast, Pacific participants were more likely to be achieving

the EAR for vitamin B12 than other ethnicities. Of greater than 30 food groups contributing to

vitamin B12, the top ten accounted for almost three quarters of the total vitamin B12 intake

and were mainly animal-based products.

6.2 Energy and B12 Intake

The prevalence of inadequate vitamin B12 intake among female adolescent participants was

substantially higher than those reported in the 2008/09 New Zealand Adult Nutrition survey

for 15 to 18 year olds (30% versus 8%) (MOH, 2011). Likewise, the nationally representative

Australian Health Survey conducted in 2012 also reported a much lower prevalence rate of

only 8% of females aged 14-18 year with vitamin B12 intakes below the EAR (ABS, 2015).

The high rate of inadequate intakes in the present study are cause for concern, particularly as

usual mean energy intakes were similar between the present study (7833 kJ/d) and female

adolescents in the 2008/09 NZ survey (8066 kJ/day) and the 2012 Australian Health Survey

(8114 kJ/day). This suggests, the diets in the present study are less vitamin B12-dense.

Among various socio-demographic subgroups, Maori adolescents had the highest prevalence

of inadequate intakes. This finding was similar to that reported in the 2008/09 national survey,

however, the inadequate intake among Maori participants were much higher in the present

study (43% versus 23.4%) (MOH, 2011). It should be noted that the present study was not a

28

representative sample of New Zealand adolescent females and sample size among ethnic

subgroups were limited.

In contrast, the findings from other more recent studies are somewhat consistent with the

results from the present study. For example, a large representative study of 10,096 Mexican

female adolescents reported a fairly similar high prevalence of inadequate B12 intakes among

participants (20%) (Pedroza-Tobias et al., 2016). Moreover, the prevalence of inadequacy was

even higher among rural Mexican adolescent females (46%) and correlated with

socioeconomic status. While the present study did not investigate urban versus rural

differences in B12 intake, both energy and vitamin B12 intakes were greater among

participants attending higher decile schools. Caution, however, is warranted with interpreting

findings based on school deciles as they are a measure of the socio-economic position of a

school’s student community rather than an individual measure of socio-economic status.

Moreover, the Mexican study presents results from an upper middle-income country and thus,

it is not entirely comparable to the present findings in New Zealand – a high income country.

6.3 Food Groups

Analyses of vitamin B12 intakes from various food items classified into 33 food groups

showed that the top three contributors to B12 intake in the present study were similar to those

reported in the 2008/09 NZ Adult Nutrition Survey; milk (15.5% versus 9.8% in the present

study), bread based dishes (11.9% versus 8.5%) and beef and veal (7.9% versus 10.0%)

(MOH, 2011). The bread based dishes category included animal-based food items such as;

burgers, meat-containing sandwiches and pizza. Although only 27% of the participants in the

present study consumed food items classified within the beef and veal food group, it was the

largest dietary contributor of vitamin B12 intakes. This demonstrates the high density of

vitamin B12 in beef, which typically contains 3.46 µg vitamin B12/100g in raw cuts, retaining

a similar concentration after common cooking methods (Bennink & Ono, 1982). In

comparison, milk contains 0.44 µg vitamin B12/100 g (Rutten et al., 2013). As such, beef and

29

veal can contribute significantly towards vitamin B12 intake in those participants consuming

animal products.

In the 2008/09 New Zealand Adult Nutrition Survey, 91.6% and 92.6% of 15-18 year old

females had consumed red meat and chicken respectively, one or more times over the last 4

weeks (MOH, 2011). Any type of milk was consumed by 94.4% of adolescent females in the

2008/09 New Zealand Adult Nutrition Survey compared to only 60% of participants in the

present study (MOH, 2011). This suggests adolescent females in New Zealand may be

consuming less milk compared to a decade ago. However, this finding must be confirmed in a

representative sample. A 250 ml glass of cow’s milk in New Zealand can contain 1.1 µg of

vitamin B12, which is over half of the EAR for adolescent females (Rutten et al., 2013). Low

milk consumption is likely one of the reasons why the prevalence of inadequate vitamin B12

intake is high in this study.

Other top contributors to vitamin B12 intakes included grains and pastas, which do not

contain natural sources of B12 but did include animal-containing food items such sushi,

lasagne, and chow mein. Sauces and condiments also ranked in the top ten and included

cheese sauces and gravies which contain animal products; and yeast extract spreads which are

fortified with vitamin B12 (Mikkelsen et al., 2018).

The major dietary food group contributors to vitamin B12 intakes in the present study

are consistent with those reported in the 2012 Australian Health Survey (ABS, 2015) although

some of the food group contributors in the Australian survey were consumed more

prevalently. For example, the Australian Health Survey found slightly higher milk (dairy and

alternatives) consumption among adolescent females (69.4%) compared to the present study

(60%) (ABS, 2015). In contrast, nearly one-third of participants in the present study

consumed egg and egg-based dishes compared to only 16% of Australian adolescent females;

and 64% of females aged 14-18 consumed meat, poultry and game dishes, compared to 54%

30

consuming poultry in the present study (ABS, 2015). Overall, there was a higher prevalence

of consumption of vitamin B12 rich foods amongst adolescents in the 2012 Australian Health

Survey, which may help explain the substantially lower prevalence of inadequate intake.

Results may also indicate distinct dietary patterns both over time and between the two

countries.

Lastly, a large, longitudinal study of American adolescent females reported a

prevalence of 16% inadequate vitamin B12 intake at 14-18 years old (Cook & Friday, 2004).

The study found that individuals who had higher intakes of grains, meat, vegetables or dairy

were significantly more likely to be meeting the EAR for vitamin B12 (Moore et al., 2012).

The data suggests general healthy eating patterns are useful in meeting vitamin B12

requirements as food groups are generally combined in a meal.

6.4 Strengths and Limitations

This study has a number of limitations. First, despite a large sample of female adolescents

recruited from seven different cities across New Zealand, including a wide range of school

deciles, the sample was not representative of the New Zealand population and cannot be

generalised. Moreover, it was difficult to explore whether any differences existed among

subgroups due to the small sample sizes within each allocated categories. Furthermore,

supplement use was not collected in sufficient detail to consider alongside dietary intake.

However,only seven participants recorded vitamin B12 supplementation so this would have

had minimal effect on mean usual vitamin B12 intake for the group. Lastly, there were no

adjustments made to account for under- or over-reporting energy intakes. One method that

could have been used to adjust for underreporting is the Goldberg method (Tooze et al., 2012)

which involves a formula for calculating basal metabolic rate and then establishing a ratio

with the reported energy intake to calculate the plausibility of the reported energy intake. It

should be noted that some of the reported low energy intakes could be due to dieting in the

participants. In the 2012 Australian Health Survey, 10.8% of females aged between 15 to 30

31

classified themselves as being on a diet (ABS, 2015). Nonetheless, a major strength was the

use of two 24-hour diet recalls, which allowed for the adjustment for day-to-day individual

variability when assessing the usual vitamin B12 intakes in our sample population group.

6.5 Conclusion

To our knowledge, this study is the first survey to describe vitamin B12 intakes of adolescent

New Zealand females in over a decade. Results of this study indicate that a high proportion of

female adolescents are consuming diets that do not meet the requirement for vitamin B12, and

may be at a risk of vitamin B12 deficiency and its subsequent health consequences (Metz et

al., 1968; Healton et al., 1991; Honzik et al., 2009; Lovblad et al., 1997). This is particularly

important given the life stage, as this group is continuing to grow and develop, and soon to be

entering their reproductive years. Further investigation into the rate of vitamin B12

inadequacy in adolescent females in New Zealand is warranted. Moreover, the findings

suggest the need for interventions to improve the vitamin B12 density of the diets of this

group.

32

7. Application to Dietetic Practice

This study has revealed concerns regarding a fairly high amount of adolescent females in New

Zealand who are not reaching their EAR for vitamin B12 intake. Dietitians need to be aware

of the potential risk of inadequate B12 intakes among adolescent female patients, particularly

those who are reducing their intake of animal-source food products. In addition, dietitians

need to be aware of the availability of vitamin B12 fortified foods which would be used in

lieu of animal products.

As this study was small and not nationally representative, these results cannot be generalised

to the New Zealand population; however, it highlights the need for further research in this

area. The rate of inadequacy found in this study is of concern as maternal vitamin B12 status

is correlated with offspring vitamin B12 status. Poor vitamin B12 status for an infant can lead

to myelination retardation, cerebral atrophy, anaemia, hypotonia and failure to thrive (Honzik

et al., 2009; Lovblad et al., 1997). Moreover, poor B12 intake can also result in megaloblastic

anaemia due to the interruption of DNA synthesis. Vitamin B12 deficiency has also been

associated with neurological symptoms (Healton et al., 1991; Metz et al., 1968). Given female

adolescents are entering into their reproductive years, the risk of suboptimal intakes may

apply beyond this lifecycle group.

This study also highlights the need for a national representative nutrition survey in New

Zealand to identify high risk groups, and design appropriate interventions. Both energy and

vitamin B12 appeared to be the highest in the decile 10 school, although it should be noted

that decile is not a true determinant of socioeconomic status. Evidence to date indicates, low

socioeconomic and rural areas tend to have the highest rates of vitamin B12 inadequacy.

Government policies and public health interventions may be required to help reduce the rate

of vitamin B12 inadequacy within these areas.

33

Although not reported in this study, the rate of vegetarianism and veganism was relatively

low in this sample. Nonetheless, the rate of inadequate vitamin B12 intake in the present

study was higher than previously recorded in New Zealand and Australia. If the true rate of

vegetarianism and veganism amongst adolescent females in New Zealand has increased over

the last 10 years, the population vitamin B12 status could be even lower. Currently FSANZ

allows voluntary fortification of vitamin B12 to plant based milks which means it is up to the

manufacturer to decide on fortification (FSANZ, 2016). As milk appears to be the main

source of vitamin B12 in adolescent females, it is important that government policy closely

monitor milk replacements to ensure they are adequately fortified with vitamin B12 and other

needed nutrients to an effective level. As there is no apparent upper level of vitamin B12,

there should be no concern about adverse effects from fortification. Further research is needed

to determine the most suitable vessels for vitamin B12 fortification amongst adolescent

females.

Overall, this study will have an influence on my own dietetic practice through highlighting

the incidence of vitamin B12 inadequacy in adolescent females. I will be more mindful of the

vitamin B12 intakes of any future clients I have as a dietitian and understand that adolescent

females are a high risk group for inadequacy. I will also aim to increase the intake of vitamin

B12 dense food such as milk and beef, fortified foods or to increase the rate of

supplementation in adolescent females who are avoiding animal-based products.

34

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9. Appendices

Appendix A. See attached file- Ethics Form

Appendix B. See attached file- Participant Information Sheet and Consent Form

Appendix C. See attached file- Dietary habits questionnaire

Appendix D. See attached file- Major food groups with listed food items