Awarding the academic title of
Master of Medicine (M Med)
Medical Faculty, University of Bern
The impact of vegan diet on health and growth
of children and adolescents – Literature review
Master Thesis submitted by
Daniel Olivier Sutter
Immatriculation Nr. (03-800-703)
Handed in 4th of July 2017
For the degree of
Master of Medicine (M med)
Supervisor: Prof. Dr. med., MSc FFPH DTM&H Matthias Egger
Institute of Social and Preventive Medicine (ISPM)
Medical Faculty of the University of Bern
Co-Advisor: MD, PhD, FMH Nicole Bender
Institute of Evolutionary Medicine (IEM)
Medical Faculty of the University of Zurich
Background: Vegan diets have enjoyed a rise in popularity within the past 6 years. However, there are few
studies on the impact of vegan diet on children or adolescent health to date.
Methods: We performed a literature review, searching the databases Pubmed and Google Scholar using
predefined search terms. We assessed what populations were hitherto used to study vegan nutrition as well as
vegan sub-populations. We included studies on critical nutrients in vegans as well as weight and height in vegan
Results: Older studies on the subject often used non-vegan convenience samples like macrobiotics, we excluded
such studies in this review. We included 21 publications on vegan diet and 14 publications on veganism in
children (1979-2017). We found that the vegan population is not homogenous and consists of sub-groups that
can vary considerably in regard to health-related beliefs and behaviour. Vegans are at a high risk for cobalamin
and calcium deficiency and an increased risk for inadequate levels vitamin D and iodine, unless proper food
planning including supplements and/or fortified foods are utilized. Ferritin levels are lower than in omnivores
but higher than in vegetarians, but this does not seem to correlate with iron deficiency anemia, as various
factors influence iron status. The risk for folate deficiency is reduced by a factor of four, while potassium and
magnesium levels are comparable with omnivores. Selenium should be included in supplementations, and
attention given towards proper intakes of zinc. Stable DHA and EPA levels can be achieved by conversion from
α-linolenic acid (ALA) in adults. It is recommended that vegan mothers use DHA supplements during
pregnancy. Vegan children need increased amounts of protein, depending on age. While growth of vegan
children is within a normal range, they are lighter and slightly smaller than omnivores.
Conclusions: Our results support the conclusion made by the Academy of Nutrition and Dietetics that a vegan
diet can be adequate during childhood and adolescence, but this largely depends on proper planning and
supplementation by the caregivers. There are vegan sub-populations that refuse supplements for ideological
reasons, and such sub-populations at increased risk should be identified in future studies in order to assess the
prevalence of nutrient deficiencies, and to allow targeted prevention. Studies are needed to assess the prevalence
and impact of various forms of supplementation in vegan diets. Future reviews on vegan diet should exclude
data based on non-vegan populations such as macrobiotics.
Table of Contents
1.1 Definition of veganism.....................................................................................................................................6
1.2 Rising popularity in recent years.....................................................................................................................6
1.3 Aims of this thesis.............................................................................................................................................9
1.4 Groups previously utilized to study veganism...............................................................................................9
1.4.1 Obsolete proxy populations for vegan diets..........................................................................................9
220.127.116.11 Black hebrew / Hebrew israelite diet.............................................................................................9
18.104.22.168 Anthroposophic diet.....................................................................................................................10
22.214.171.124 Macrobiotic diet.............................................................................................................................10
1.4.2 Types of vegan diets...............................................................................................................................11
126.96.36.199 Standard vegan diet.......................................................................................................................11
188.8.131.52 Rastafarian vegan diet...................................................................................................................12
184.108.40.206 Raw vegan diet...............................................................................................................................12
220.127.116.11 „Natural“ vegan diet.......................................................................................................................13
1.4.3 Summary on utilized groups to study veganism.................................................................................13
2 Narrative Literature Review........................................................................................................................................15
2.1 Introduction, methods and delimitations.....................................................................................................15
2.2 General assessment of vegan nutrition.........................................................................................................15
2.2.1 Advantages of vegan nutrition..............................................................................................................16
2.2.2 Risks of vegan nutrition........................................................................................................................16
2.3 Brief overview over nutrients that are not focus of this thesis..................................................................16
2.3.2 n-3 (Ω-3) Fatty Acids............................................................................................................................16
2.4 Children and Adolescents...............................................................................................................................18
2.4.1 A summary on infancy...........................................................................................................................18
2.4.2 Older children and adolescents.............................................................................................................19
Iron deficiency in vegan children
18.104.22.168 Vitamin D.......................................................................................................................................25
22.214.171.124 Cobalamin (Vitamin B12).............................................................................................................29
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126.96.36.199 Folate / Folic acid..........................................................................................................................35
188.8.131.52 Weight and Height........................................................................................................................37
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2.5 Summary of the narrative literature review.................................................................................................43
3.1 Study populations...........................................................................................................................................46
3.2 Narrative literature review.............................................................................................................................47
3.3 Swiss public health policy..............................................................................................................................49
3.4 A case for a broader view on dietary effects on health................................................................................51
8 9 *
3.6 Strengths and limitations...............................................................................................................................57
I'd like to thank Prof. Dr. med. Matthias Egger, Director of the Institute for Social and Preventive Medicine
(ISPM) at the University of Berne for his openness for the plans of my thesis and his supervision. I thank Prof.
Dr. Marcel Zwahlen for his kind and generous co-advising on statistical issues, and especially Dr. med. Nicole
Bender for co-advising and guiding me with much enthusiasm and expertise throughout the process of
researching and writing. Many thanks also to Dr. Benita Combet, who pointed out the KiGGS dataset to me. I
feel grateful for the kind exchanges I've had with other researchers and professionals, such as Prof. Dr. Bodo
Melnik, Prof. Dr. Martin Fiedler, RD Jack Norris, MS RD Ginny Messina and Gabriela Müller.
I'm glad to say that the entire thesis was written using free and open-source software, as it is my conviction that
research and education should be accessible to everyone. Therefore, I'm thanking the world-wide community
that has provided the tools to do so, namely LibreOffice (text editing), Zotero (citations), and GNU-Linux
Lastly, I'd like to thank the Department of Education and Culture of the Canton of Solothurn, Switzerland, for
generously providing a loan for finishing my education in the field of human medicine, and having previously
supported me throughout my studies in psychology, which has enabled me to do research more effectively.
1.1 Definition of veganism
In this thesis, I will use the term to refer to ## , which means milk and eggs are
included. Further, I will use the now predominant term to describe what sometimes used to be called
, even though veganism explicitly avoids exploiting other species for any purpose, not just
food, while strict vegetarianism could only be a diet form.
So what is the exact difference between vegetarianism and veganism? Both abstain from eating meat (including
chicken, insects), fish and seafood. Vegans, however, eschew all products derived from animal exploitation.
Despite veganism having no central authority, most vegans would agree with the definition used by the British
% . .&73373
Concerning food, this includes mainly dairy, eggs, and honey. Another main area is clothing, where materials
such as leather, wool, feathers or silk are avoided. Practices where instead of animal products the animals
themselves are used are also shunned, such as zoos or certain circuses. Because these goals are often in conflict
with living in today's societies, the definition explicitly states that the adherence should go
However, for most vegans there is little to no tolerance in regard to foods, probably because it is
comparatively easy to completely avoid animal products altogether in this area, and labels and legislation clearly
define what foods can be considered vegan without any exceptions.
Vegetarian diets have been existing since antique times, with Pythagoras being one of the earliest prominent
recorded advocates, yet explicitly vegetarian diets without dairy or eggs appeared only at the beginning of the
19th century. In 1944 Scotland, a small group led by Donald Watson created the term by symbolically
cutting out the middle letters of the word . From Scotland, veganism spread to other countries, but
only making up an insignificant fraction of the population for over half a century.
1.2 Rising popularity in recent years
At some point around the year 2011 there has been a wide-spread surge of interest in veganism, as defined by
web searches containing the word ; <(https://www.google.com/trends/). At the end of the following three
year period, in 2014, the relative interest has increased by a factor of 30 in China, by a factor of 20 in Australia,
by a factor of 8-15 in most European countries (UK, Ireland, Norway, Sweden, Finland, The Netherlands,
Belgium, France, Spain, Portugal, Italy, Germany, Austria, Poland, Slovenia, The Czech Republic, Romania,
Greece, Turkey) and Iceland, by a factor of 5 in Peru, Croatia and Israel, by a factor of 4 in Mexico, Canada,
Serbia and New Zealand, by a factor of 3 in Chile and by a factor of 2 in the United States, Argentina, India,
Japan and South Africa. Interestingly, no positive trend at all could be seen in Russia or countries oriented
towards Russia like Belarus or the Ukraine, as well as Iran, and only a marginal rise of interest can be seen in
Venezuela, Colombia, Brazil, Jamaica, Bosnia & Herzegovina and Egypt. Especially in these latter instances with
no or only weak effects, it is possible that usage of native language terms not using the stem ; < were used
instead, and indeed this effect may have modified overall results. However these numbers illustrate the
magnitude and the globality of the phenomenon. As an example of how these Google Trend charts look like,
; < queries in Switzerland, the origin of this thesis, are presented in .
Figure 1=5 >; <!.9!,75 =
These numbers are in accordance with a 2006 study which noted that veganism was gaining traction especially
in affluent countries2. A 2007 UK survey on 3618 individuals showed that 2% identified themselves as vegans,
while a survey conveyed in 2013 showed 1% of Australians identified as vegans2. A 2014 survey showed that 5%
of the Israelis were vegans2, and a 2016 nationwide poll in the United States of America estimated that 1.52% of
adults were following a vegan diet (46% of all vegetarians)3. In Germany, it was estimated that as of 2014, about
1% of the population were estimated to be vegans2. A representative survey conducted in 2017 found that 3% of
the general Swiss population was vegan A B, with the highest percentage of vegans (6%) in the
demographic aged 15-34 years, while only 1% of people older than 34 years were vegans. 56% of these vegans
adopted their lifestyle within the prior two years, another 37% within the prior ten years A B. Only 2% of
these vegans switched 11-30 years prior to the survey. The survey also found that vegans tended to be male
(60%), live in urban areas and have completed higher education (47%)4. The aforementioned data suggests that
the interest registered by Google Trend closely correlates with actual conversion to veganism.
Figure 2.1=4 !.24
Figure 2.2= !.24
Reasons for this wave of interest are manifold. A 2014 survey on 329 vegans conducted in 7 German
supermarkets assessed that 89.7% had animal-related motives, 69.3% personal wellbeing and/or health, and
46.8% environment-related motives5. For 81.1%, motives of two or more of these three motive clusters were
relevant, and all of them are probably part of our Zeitgeist. A 2017 survey conducted in Switzerland painted a
similar picture, with animal welfare and ethical reasons being the most important motivation (78% and 60%),
followed by ecological reasons (58%), global food security (40%) and lastly health reasons (35%) playing lesser
roles A $B4.
Figure 3=8!. 24
It was observed that health reasons seem to be increasingly determinative for the adoption of veganism over the
last two decades2. Another reason might be that information on veganism has been able to be accessed and
shared instantly and globally over the internet in general, and especially over communication platforms like
social media. Further, the media did not only help its relative popularity with serious portrayals and discussions
on key issues of veganism, but also through articles or TV segments which ridiculed or scandalized the topic,
thereby still giving it a platform and enabling a public discourse.
In the light of this trend, more wide-spread scientific interest in this from a traditional perspective rather radical
diet is only now surfacing. Laypersons as well as experts are sometimes quick to see either dangers or benefits of
this diet, but scientific and especially epidemiological investigations of many claims are sparse. Furthermore,
because nutrition plays a more pronounced role during pre-natal development and during childhood as well as
adolescence, scientific clarity about risks and benefits are vital for the protection of children being raised on a
vegan diet on one hand, as well as for protecting responsible vegan parents from excessive scrutiny, on the other
1.3 Aims of this thesis
The goal of this study is to focus on the effect of a vegan diet on the health and growth of children and
adolescents. In a first step, it is specified what the population of interest, vegans, precisely consists of. This will
be done by separating the vegan population from other, superficially similar populations who have been used in
older studies as proxy populations for vegans. Furthermore, because of its heterogeneity, the vegan population
itself will be divided into smaller sub-units. This new approach within studies on vegan nutrition will enable a
more precise identification of risk populations, which should ultimately form the basis for more targeted health
prevention. Subsequently, advantages and disadvantages of vegan nutrition will be discussed in relation to key
nutrients, using evidence from both adults and children to assess the risk of experiencing or avoiding
malnutrition. Lastly the influence of vegan nutrition on anthropometric variables such as weight and height will
be investigated. These results will be summarized and put into context of current Swiss public health policy, and
finally broader health effects of dietary choices as mitigated by animal farming will be examined.
1.4 Groups previously utilized to study veganism
1.4.1 Obsolete proxy populations for vegan diets
Because vegan subjects were hard to find until recent decades, older research, such as an often cited study
published in 19886, used proxy populations to come to conclusions about vegan diets. We will subsequently
discuss the three main reasons why these proxies are unsuited to study health effects of modern vegan diets.
They all sustain a religious or spiritual belief system which leads to an incomplete adoption of a vegan diet, often
with a concurrent rejection of the necessary supplementation of cobalamin (vitamin B12).
184.108.40.206 Black hebrew / Hebrew israelite diet
Black Hebrews, meaning African-Americans identifying themselves as Jews, surfaced in the United States
around the turn to the 20th century. Their eating habits are derived from the bible, with most adhering to kosher
diets and some interpreting the scripture as recommending a vegetarian or even a vegan diet. Hence, only a
fraction of black Hebrews are nutrition-wise vegans, and supplements were not used6, likely because they were
of course absent in the related passages in the bible.
There is one often cited study on this population, called „84!
% "<, where 4 infants were severely undernourished and 1 infant died. While these three
infants had an uneventful recovery, parents still refused to give their infants vitamin B12 supplements7.
220.127.116.11 Anthroposophic diet
Anthroposophic lifestyle is a life philosophy with a holistic view on health combined with various spiritual
ideas, based on the works of its founder, Rudolf Steiner . Organic foods are promoted and the use of antibiotics
and antipyretics discouraged. Anthroposophes are also known for their very low vaccination rate which is
estimated from 0.6 up to 65.4%, making them prone for outbreaks of infectious diseases such as measles. This is,
among other reasons, due to the prevalent belief that measles infections strengthen children's development8.
There is no evidence that animal products such as milk or eggs are avoided within this belief system, even
though supplements reportedly have been used6.
18.104.22.168 Macrobiotic diet
Macrobiotic diet is associated with Zen Buddhism and based on the idea of balancing yin and yang. It was
popularized in Japan by the philosopher George Oshawa in the 1930ies. Being probably the most popular proxy
for studying vegan nutrition, macrobiotic diet was used in the 1980ies as a proxy and sometimes even as a
synonym to vegan diet6. However, because there are significant differences in both the foods and beverages and
psychosocial population properties between people living on macrobiotic and vegan diets, this led to false over-
generalizations, which had to be revised by studies on representative vegan populations. Nevertheless, studies
using macrobiotic diet as a proxy for vegan diet still are the basis of the rejection of vegan child nutrition by
some national institutions such as the Deutsche Gesellschaft für Ernährung (German Society for Nutrition) 9 and
international institutions such as the European Society of Pediatric Gastroenterology, Hepatology and
Nutrition10 as late as 2008, even though the latter organization dropped this equivalence in January 2017 and
now tolerates vegan child nutrition ;
> . <11.
To illustrate the shortcomings of this proxy population, a few noteworthy differences are now being presented.
The basic difference is that both in veganism and macrobiotics, the diet is just one aspect of a lifestyle that
strongly moderates nutrition. For example, macrobiotic nutrition is tailored according to age, sex, level of
activity, personal needs and the environments12. Macrobiotics do not only, for the most part, avoid meat,
poultry and milk products, but also shun plant foods like tomatoes, and deemphasize fruits in general, which is
problematic regarding vitamin C intake12,13. They also avoid vitamin supplements, which would be crucial
regarding cobalamin (vitamin B12), vitamin D, calcium or iron, as discussed later on. Technologies like teflon
pans or microwave ovens are shunned as well13. This pattern may seem erratic and is a result of abstract
concepts that relate not at all or only marginally to western science. For example, foods are mostly reduced to
the dualist life force called yin and yang. Balancing yin and yang is believed to lead to health, while imbalance is
believed to lead to illness. This balance is not only dependent on the foods ingested, but also on one's body, the
local climate, the season, and the way foods are prepared and combined. Because macrobiotics is not empirical
science, advice on which foods should be avoided varies strongly among the experts. Raw foods should only be
consumed in small amounts due to assumed cooling effects they have. The shunning of vitamin supplements,
teflon pans and microwaves could be viewed as a general distrust towards western science. Interestingly, in a
1996 ethnological study13, macrobiotics were compared to animal-right activists (of whom many were vegans)
in regard to their attitudes towards nutrition. Macrobiotics showed much diversity in reasoning about foods
which should be excluded, and novices were primarily following advice of those experts. Animal-right activists'
reasoning, in contrast, was described as scholarly and relied on philosophical (e.g. the right to live), biological
(e.g. small biological differences between humans and other animals) or health-related arguments (carcinogenic
effects of red meat, cholesterol), suggesting two very distinct population with different styles of gathering
information and reasoning. This difference is crucial when implementing a balanced, evidence-based vegan diet
1.4.2 Types of vegan diets
A poor, e.g. fast-food based omnivore diet is not regarded as representative for the quality of an omnivore diet
in general, or even for a well-planned omnivore diet. The same differentiated view should be applied to vegan
diets. Because this principle tends to be neglected, individual examples of poor vegan diets have had and still do
have a strong influence on expert opinions, both in research and clinical settings, where naturally only failed
attempts of vegan diets are presenting themselves. As early as 1988, Sanders et al. stressed the importance of the
distinction between adequate and inadequate vegan diets, and stated that if vegan parents are aware of possible
pitfalls and therefore provide an adequate vegan diet, their children will thrive like their omnivore peers14.
22.214.171.124 Standard vegan diet
After the 1960s and 1970s, there has been a shift of the vegan population from counter-culture and spiritual
orientation towards mainstream. In 1994, Mangels and Havala called thoseC.CvegansC15. With rapid growth
of the vegan population within the last six years, as described earlier, it can be assumed that those ;.C vegans
are overwhelmingly defining modern populations. Today, the major national vegan umbrella organizations,
such as the Vegan Society16 (United Kingdom), the Vegane Gesellschaft Deutschland17 (Germany) or the Vegane
Gesellschaft Schweiz18 (Switzerland) are central authorities for most of these vegans, and generally urging
vegans to consider crucial nutrients, including cobalamin, calcium and iron, with a mandatory supplementation
of at least cobalamin. Even though these guidelines could often be improved, those recommendations form a
basis for what could be called a well-planned, adequate diet that I would call the standard vegan diet, and its
adherents standard vegans.
126.96.36.199 Rastafarian vegan diet
Rastafarians in general follow the so called ital diet. In most cases it can be viewed as a vegetarian diet with a
focus on ;< ingredients. Therefore, preservatives and sometimes iodized, non-kosher salt is avoided,
sometimes a vegan diet is followed. Rastafarians are often alienated from the rest of society. Because of this, they
may be less accessible to evidence-based dietary advice, as suggested by the shunning of iodized salt. The
Rastafarian belief is centered around and mostly confined to Jamaica, where in 2011, around 29'000 individuals
identified themselves as Rastafarians. Because only some Rastafarians are following a vegan diet, and because
they further restrict their selection of foods on a religious basis, studies on Rastafarian vegan diets are hardly
representative of vegan diet in general. This population was mostly used in the 1980's, before populations with
more external validity were available.
188.8.131.52 Raw vegan diet
Advocates of raw nutrition hold an array of beliefs which are not evidence-based. To illustrate this, a brief
description of three main issues is provided, namely the heating of foods, the idealized role of ;<foods and
consequently the role of gluten. Concerning the first issue, it is commonly wrongly assumed that the degrading
of vitamins through heating greatly affects most if not all vitamins, whereas indeed only vitamin C and
carotenes are affected to a larger degree, and applying heat can actually make protein and certain carotenoids
more accessible19,20. An often stated claim proponents of raw diets is that plant enzymes are important to the
human body and should therefore not be degraded by heat – ignoring the breakdown that will inevitably occur
through stomach acid and specialized enzymes like pepsin, trypsin and chymotrypsin, or that there is no such
thing known as ; 9<. These concepts therefore are often based on an incomplete
understanding of the underlying biology. In the scientific literature there is only thin evidence for defending the
general avoidance of heating food, for example the benefit of a faster excretion of carcinogens through higher
fiber content or the Maillard reaction, in which sugar cross-links and destroys amino acids, peptides or proteins,
or by which pro-inflammatory products are generated20. Heating of proteins can also create mutagenic
compounds20, as is commonly known from frying. These effects seem rather mild and are likely outweighed by
the benefits of heating. Followers of raw diets often hold the simplified belief that processed food will always be
less natural and therefore less healthy. In this regard, wheat products are avoided, for they usually have to be
heated before consumption. This avoidance tends to be cemented by the additional belief that the wheat protein
fraction gluten itself is a threat to human health. Vitamin supplements are generally considered unnatural and
unnecessary, an essential problem that will be discussed in the next paragraph. Within followers of raw diets in
general, insufficient energy supply is a large problem, in one study population affecting 43%, and is regularly
associated with loss of body weight and amenorrhea in adults21. From an evolutionary perspective it has recently
been argued that through a rise in energy availability, controlling fire and cooking had a significant evolutionary
significance, possibly being a more likely explanation for the near doubling of neurons between D and
D than the older hypothesis of increased raw meat consumption. The key argument is that the human
brain is significant in its energy demand, consuming 20% of the total available energy while representing only
2% of body mass. Cooking has not only drastically increased available energy, but also minimized time spent for
food acquisition and preparation, effectively freeing up time to put added neurons to their competitive
advantage22,23. This evidence suggests that we have indeed evolved through adaptation to cooking, and raw diets
are not optimal for current humans. In regard to individual human growth, the aspect of low energy density in
uncooked foods can be highly problematic, especially during childhood and adolescence. Lastly, the high amount
of fruit and vegetables present in raw food diets has been shown to increase risk for dental erosion by a factor of
184.108.40.206 „Natural“ vegan diet
This group includes most rastafarian vegans, raw vegans, but also hitherto unclassified vegans, as the basic line
of arguing is in fact wide-spread in western culture in general. This argument is known under the name
, meaning the simplistic notion that nature is good, while non-nature is bad. The term „C can be
extremely ambiguous itself25, but is often used to identify the part of our universe which is untouched by
technological human influence. This domain is revered as a perfect, balanced, just and good-willing entity. This
mentality leads to some positive conclusions on one hand, but to outright dangerous conclusions on the other
hand. For example, it motivates people to ; &<, which can promote eating more home-cooked or
fresh foods, spending more time outdoors, and other healthy behavior. It can also promote appreciation of
plants and fellow animals. On the other hand, romanticizing nature tends to foster an inherent distrust towards
human technology. While basic human technology like housing, clothing, fire or non-electric tools are still
considered natural (or not regarded as technology at all), some technology beyond an arbitrary point is not
thought to be natural anymore. The basic fallacy here is that it is indeed to increasingly use
technology to shape the environment. Unfortunately, perceived ;<technology can include a wide array
of modern medical achievements. Lab testing, supplementation of micro-nutrients, or pharmaceutical medicine
(antibiotics, vaccinations, chemotherapy) can be rejected for this reason. To describe this behavior, the term
chemophobia has been used26. At the same time, having a bias of only seeing the good in nature can make people
underestimate dangers related to pregnancy, birth, preventable disease (e.g. by vaccination), or as is the topic in
this thesis, child nutrition. Science-based information on nutritional needs and supplementation and/or
fortification is crucial for any diet, especially in regard to pregnancy and childhood. Since this holds true even
more so for vegan diets, this ideology is highly problematic within this population.
1.4.3 Summary on utilized groups to study veganism
Because a vegan diet is the focus of this study, only representative vegan groups were taken into account. Studies
on black hebrew, anthroposophic, macrobiotic and rastafarian-vegan diets are omitted, because those samples
cannot be regarded as representative for the general vegan population. Mangels and Havana stated as early as
199415, such populations only partially adhere to a vegan diet and often reject supplementation, due to religious
or spiritual motivations. However, it is likely that, depending on the sample, the inclusion of a considerable
;< vegan proportion, including raw vegans, can lead to unfavorable and in sum at least partially non-
representative results. As we saw, these groups tend to reject supplementation and often show distrust towards
evidence-based medicine. For raw vegans, energy adequacy and dental erosions are further special concerns,
especially during the process of growth. Further dissecting vegans into groups of people who are open or closed
in regard to scientific approaches in nutrition and health, with the example of chemophobia, could tell us more
about the nutritional adequacy of a science-based vegan diet which was previously defined as the standard vegan
diet, while at the same time opening up a discussion on ways to disseminate sound information among groups
who are at risk. This is especially relevant during growth, which is the focus of this thesis.
2 Narrative Literature Review
2.1 Introduction, methods and delimitations
Despite the attempt to include all relevant studies, this is not a systematic literature review. A systematic review
would have been complicated by the multitude of research questions taken into account, with for example each
nutrient being separate field of research with sometimes few to no studies conducted on vegan children or
adolescents. The format of a narrative review therefore seems more adequate.
Nutrition is an extremely broad and complex subject, and therefore only a fraction of nutrients and health-
related outcome variables will be examined in this thesis. The focus lies on nutrients relevant to vegan diet that
are at the same time assessed during blood sampling in the KiGGS study, which will be examined in my
following M.D. dissertation. The KiGGS study contains cross-sectional data from a German sample of 17'652
children was assessed between the years 2003 and 2006, containing 61 children who were following a vegan diet
pattern and 75 children following a vegetarian diet pattern between the ages of 1 and 17 years.
Nutrients where only intakes were available were omitted, due to the fact that the measurement can be
imprecise because of lacking evidence in actual nutrient status. These omitted variables are vitamin C, vitamin A
/ beta-carotene and iodine. For some relevant nutrients, such as, protein, zinc, riboflavin (vitamin B2), fiber,
calories, and fatty acids, none or no exact data is available in the KiGGS dataset. However, deficiencies in those
areas would likely impact growth, an outcome variable that will be examined.
Nutrient status was available for iron, calcium, vitamin D, cobalamin (vitamin B12), folate, potassium, and
magnesium and will be the focus of this literature review, complemented with data on weight and height.
Databases utilized were PubMed and Google Scholar. Keywords included ; E< or ; C in
combination with the terms ;<, ;<3;<, ;< as well as in combination with the respective
names of researched nutrients or anthropometric terms such as ; <, ;. <, terms relating to growth, such
as;<, ; .< As the results on vegan populations were limited, all available types of studies were
taken into account, and reference list checking of from review articles has been applied to complement my
findings. The website % D , run by the registered American dietitian Jack Norris has also been of
valuable in finding scientific literature in regard to vegan nutrition.
2.2 General assessment of vegan nutrition
In 2016 the Academy of Nutrition and Dietetics (AND; until 2012 known as the American Dietetic Association),
the world's largest organization of food and nutrition professionals, has published a comprehensive review on
vegetarian and vegan nutrition27. Therein, researchers concluded that vegan diets are appropriate for all stages
of the life cycle, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, as well for
athletes. They summarize the advantages and risks as follows.
2.2.1 Advantages of vegan nutrition
Vegan and vegetarian diets offer significant benefits when compared to standard western diets, such as a
reduced risk for ischemic heart disease, type 2 diabetes, hypertension, certain types of cancer, as well as obesity.
Main reasons for this are the low intake of saturated fat and high intakes of whole grains, vegetables, fruits, nuts
and seeds, many of them rich in fiber and phytochemicals, which lead to lower total and LDH cholesterol and
improve serum glucose control27.
Apart from direct effects on health, the environmentally sustainability of vegan diets must be considered as well.
Vegan diets use fewer resources and are inflicting much less environmental damage than diets rich in animal
products27. Further benefits will be presented in the discussion.
2.2.2 Risks of vegan nutrition
Concerns of vegan diets are reduced intakes of certain nutrients, which can be readily avoided by appropriate
planning, including substitution27.
2.3 Brief overview over nutrients that are not focus of this thesis
Due to the scope of all possible nutrients, only those whose status was assessed during blood testing in the
KiGGS dataset were examined in depth. Nonetheless, to complete the picture, the key points of those nutrients
which will not be further examined, protein, n-3 (Ω-3) fatty acids, iodine and zinc, will be presented briefly in
paraphrased form as they were summarized by the Academy of Nutrition and Dietetics, with punctual
elaborations from their cited primary literature27.
Protein needs of vegan children might be slightly higher due to differences in protein digestibility and amino
acid composition, leading to a recommended increase of protein consumption by 30-35% in vegan children aged
1-2 years, 20-30% for vegan children aged 2-6 years and 15-20% for vegan children aged more than 6 years,
compared to standard recommendations. However, when overall caloric intake is adequate, vegan diets typically
meet or exceed recommended protein intakes27. When a variation of plant foods is used, especially legumes and
soy products, all essential amino acids along with other nutrients are supplied by a vegan diet27.
2.3.2 n-3 (Ω-3) Fatty Acids
Vegans have α-linolenic acid (ALA) intakes similar to omnivores, but long-chain n-3 fatty acids like
eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are typically absent in vegan diets, as they are
rarely supplemented, leading to DHA and EPA plasma, blood and tissue concentration which are 40-50% lower
when compared to omnivores27. DHA and EPA are used for the development and maintenance of the brain,
retina, and cell membranes and have a positive impact on pregnancy outcomes as well as the risk for
cardiovascular disease and other chronic diseases. Despite these circumstances, no impairment of vegan diet on
visual or mental development or age-related dementia has been found, and vegan adults have a reduced risk for
cardiovascular disease instead of an increase27. In the absence of convincing deleterious effects, the clinical
relevance of decreased DHA and EPA levels in vegans is currently an open question. The endogenous
conversion of ALA to EPA and DHA is inefficient, but evidence suggests that it is sufficient to lead to stable
DHA and EPA levels over many years. This process is dependent on metabolic genetics, age (decline with age),
sex (less conversion in young males), health status (chronic disease, smoking), and dietary composition. Trans-
fatty acids and excessive use of alcohol and caffeine inhibit conversion, as well as any amount of (γ, also called n-
6 or Ω-6) linolenic acid (LA). For the latter reason it is recommended that intakes of (γ-)linolenic acid (LA) to
α-linolenic acid (ALA) should not exceed a ratio of 4:1. The best plant sources for n-3 fatty acids (ALA) are
various seeds (flax, chia, camelina, canola, and hemp), as well as walnuts and their oils. For vegans with
increased needs, such as pregnant or lactating women, or with decreased conversion ability, such as elderly
vegans or those suffering from hypertension or diabetes, micro-algae-based DHA supplementation of 200-300
mg/d is recommended, and have shown to lead to significant increases in DHA status 28. Algae have been
confirmed to reliably and considerably increase DHA status in vegan and vegetarian populations in a recent
Adult vegans show similar to slightly reduced intakes of zinc, as well as physiologically lower serum zinc
concentrations than omnivores27. No adverse health consequences could be attributed to these lower
concentrations, and overt zinc deficiency is unknown in Western vegans 27. Unfortunately, there is insufficient
data on zinc levels for populations with the highest risks for deficiency, such as older adults, pregnant and
lactating women as well as children. Good vegan sources of zinc are soy products, legumes, grains, seeds and
nuts. Sprouting or in the case of bread leavening can reduce the binding of zinc by phytic acid and thereby
improve the bioavailability of zinc27.
Vegans not consuming iodized salt or sea vegetables may be at risk for iodine deficiency27. Even though
soybeans, cruciferous vegetables, and sweet potatoes contain goitrogens, meaning substances that interfere with
iodine uptake in the thyroid gland, none of these substances have shown to be associated with thyroid
insufficiency in healthy people with adequate iodine intake27.
2.4 Children and Adolescents
The first comprehensive article on vegan nutrition for children goes back as early as 1988 14. The author came to
the conclusion that there is an important discrimination to be made between appropriate and inappropriate
vegan diets. Although this differentiation seems natural when omnivore diets are discussed, isolated cases of
inappropriate vegan diets tend to lead health experts to the conclusion that vegan nutrition is per se inadequate.
However, the author concluded that it is well possible to raise vegan children without physical or intellectual
drawbacks. A major comprehensive review on the topic was published in the form of two articles in in 2001 by
Virginia Messina30,31. For the purpose of this thesis, her results are expanded by further evidence that has
accumulated over the last fifteen years. Because the scope of this summary is already extensive, pregnancy is
omitted, and data starting with infancy will be presented next.
2.4.1 A summary on infancy
A 2001 article summarizes key aspects of vegan nutrition in infants30. Therein, the American Dietetic
Association (after 2012 known as the Academy of Nutrition and Dietetics) and the American Academy of
Pediatrics state that vegan diets can be appropriate for normal infant growth, a statement that the Academy of
Nutrition and Dietetics has renewed in 201627. Vegan mother's breast milk is equal to non-vegan breast milk,
with the exception of fat composition. Vegan breast milk contained less saturated fat and eicosapentaenoic acid
(EPA) and more linoleic (18:2n-6) acid and linolenic (18:3n-3) acid30. A 2005 literature review came to the
conclusion that randomized controlled trials comparing infants fed formula with vs. without DHA failed to
consistently show positive effects on mental and motor tests or visual acuity. The strongest evidence for an
effect of DHA seems to stem from animal studies who were conducted under severe dietary conditions. The
authors suggested that effects might be significant, but are perhaps too small to be measured 32. Inconsistent
results were also reported in a 2009 systematic literature review33. This is in accordance with the previous sub-
chapter on n-3 (Ω-3) fatty acids, citing no impairment of vegan diet on visual or mental development or age-
related dementia, and vegan adults having a reduced risk for cardiovascular disease instead of an increase. This
suggests that endogenous synthesis in vegans might be sufficient. Still, as of 2016, the Academy of Nutrition
suggests DHA supplementation to vegan mothers who are pregnant or breast-feeding27.
The American Dietetic Association recommends that vegan infants should be breastfed for the first year, if
possible, with soy-based formula as a viable backup solution30. One cohort study looking at the general health of
adults who were fed soy formula as infants found no evidence for impaired thyroid or reproductive
functioning34. Further studies have confirmed the absence of adverse effects on growth, development or
reproduction in term infants35,36. The American Academy of Pediatrics recommends monitoring and possibly
increased doses of levothyroxine when feeding soy formula to infants with thyroid problems and no soy formula
at all in pre-term infants, because cow's milk formula designed for pre-term infants has been shown to lead to
better bone growth compared to standard soy formula36. If maternal cobalamin is inadequate, breastfed infants
need substitution. It is controversial whether or not older infants need zinc supplements. In any case, reliable
sources of iron, vitamin D as well as the aforementioned cobalamin are necessary. Vitamin D can be supplied
non-dietary, as 30 minutes of sunlight wearing only diapers or 2 hours of sunlight with regular clothing
including a hat, enables the skin to synthesize sufficient daily amounts30. However, some researchers would
recommend dietary supplementation to protect infants and small children from UV radiation damage37.
2.4.2 Older children and adolescents
The KiGGS dataset provided data on nutrient status of iron, calcium, vitamin D, cobalamin (vitamin B12),
folate, potassium, and magnesium, as well as anthropometric variables such as weight and height. These
variables will now be examined. Because cow's milk and its products is a main difference between the more
established vegetarian diet and the vegan diet, a separate chapter is dedicated to its health-related benefits and
To start off with biology, it has long been known that bioavailability of iron from meat (heme iron) is higher
than the one of plant origin (non-heme iron). From this fact it has often been concluded that therefore meat
must be included in the diet to avoid iron deficiency. However, the matter is more complex because iron
absorption is strongly dependent on iron status and nutritional habituation, because of the recently discovered
and potentially high bioavailability of plant ferritin and because multiple plant- and animal-based nutrients are
both positively and negatively modifying iron absorption. Those issues will be discussed in the following
Due to the fact that the human body lacks iron excretion, iron absorption is highly regulated and dependent on
iron status. In the case of deficiency, iron uptake of both heme and non-heme iron can increase 10-fold38. It is
also possible to adapt to low intakes of iron over time by reducing iron losses 39, with one study demonstrating
that over a period of 10 weeks of consuming iron with low bioavailability, absorption increased by almost 40% 40.
Individuals used to non-heme iron can also absorb it more effectively40.
In-vivo studies in humans showed that ferritin, due to its relative thermal stability (it is partially stable above
temperatures of 80°C41), pH stability and the protection by the food matrix it is embedded in, ferritin is mostly
not degraded by digestion and therefore can be absorbed by endocytosis in the small intestine. This novel
pathway can be a considerable factor in the absorption of plant iron. It is also speculated that due to the
encapsulation of the iron within the ferritin, it might be safer than other forms of iron, because there is limited
contact with other food ingredients and/or the cells of the digestive tract as well as a slower release of iron
during its degradation. A molecule of ferritin typically contains a maximum of around 3000 iron atoms. Legume
seeds like soybeans, chick peas, lentils or lupine are especially rich in ferritin38.
A vegan diet is richer in phytates and other plant factors such as dietary fiber, which are decreasing
bioavailability of non-heme iron31,42. Adding to this, polyphenols such as tannic acids, contained in cocoa, coffee,
green or black tea, but also many herbal teas, are also inhibitors of iron absorption43. For example, one study
showed that after only two weeks of drinking 1 L/d of green or black tea, plasma ferritin levels were
significantly reduced, but only in women with basal ferritin levels below 25 μg/L44.
Compensating effects of these inhibitions can be the higher content of vitamin C in a vegan diet 31, or other
organic acids42, such as lysine45, an amino acid prevalent in legumes. Even though a study on young vegan
women found no correlation between ferritin serum concentration and enhancers (vitamin c, other organic
acids) or inhibitors (phytates, dietary fiber)42, another study has shown that vitamin C has the potential to
overcome those inhibitors, starting at a dosage of 50 mg (the vitamin C content of a small orange), and boosting
absorption to 130% at 150 mg46. Indian researchers found that large doses of Vitamin C (500 mg) twice a day
after meals increased iron status more effectively than iron supplements did47.
A more exotic way of improving iron status has been demonstrated by Brazilian researchers. Water-based,
acidic foods such as tomato sauce can take up iron from the iron skillets they are cooked in, reducing prevalence
of anemia from 32.1% to 5.3% over the course of 12 weeks in the presented study48. When iron cookware is used
for brewing beer, even dietary iron overload can occur, a phenomenon also known as Bantu siderosis. A similar
way of improving iron is by using fish-shaped (for psychological reasons) iron ingots, such as the Lucky
or the D, to boil for 10 minutes in any liquid or broth based meals to enrich food or drinking water
with iron. This method seems to be, like iron skillets, an effective means of improving iron intake in countries
lacking affordable and accessible means to do so otherwise49.
Adding to that, the absence of cow's milk is also improving comparative iron bioavailability in vegans.
Consumption of cow's milk negatively affects iron status in two ways. Firstly, cow's milk inhibits dietary iron
uptake of humans of all ages, making it the most likely cause for iron deficiency in children aged two to three
years50. This effect is due not only to its calcium content (iron absorption is reduced to 50-60% at doses of 300-
600mg Ca) of milk, but is exaggerated by other agents contained in milk, such as casein51, since as little as 165
mg of calcium from milk or cheese also reduced iron absorption by 50-60%. It is worth noting that calcium-
chloride inhibited iron absorption in the same way as milk or cheese did52. Furthermore, cow's milk intolerance
can be a source of occult blood loss, with early milk introduction (5 to 6 months) leading to heme-positive stools
in up to 30% of all infants.50.
Because calcium of any source can significantly inhibit iron absorption, German researchers recommend
supplements containing at least 60 mg of iron with good bioavailability and no more calcium content than 250
mg for vegan women 42.
The absence of eggs is also a factor improving comparative bioavailability of dietary iron in vegans, as egg
protein has been demonstrated to inhibit iron absorption twice as effective as casein or whey protein51.
Regarding iron status in adults, even though ferritin levels are lower, vegans did not show higher rates of
anemia than people in the general population31, a finding that has been repeatedly observed before53. An
experimental study has shown that physiologically lower ferritin levels can be beneficial, because reducing
ferritin levels (in the cited study from 122.5 ng/ml to 79.7 ng/ml) is associated with a decreased cancer risk54.
Elevated serum ferritin, on the other hand, has been associated with the risk of developing metabolic syndrome
over a 5 year period with many common confounding variables controlled for, suggesting an independent
association55. When comparing heme to non-heme iron, people with the highest heme-iron intake suffered a
18% increase in colon-cancer (RR = 1.18; 95% CI: 1.06-1.32), as a recent meta-analysis has shown56.
The findings regarding iron status are consistent with a Swiss study published in 2015 of 206 adults ranging
from 18-50. Regarding the median of plasma ferritin, no significant differences were found between the
omnivore (58; range = 3-463 μg/L) and vegan group (40; range = 9-277 μg/L), however the vegetarian group
(32; range = 7-184 μg/L) scored significantly lower than the omnivore group. In this regard, the authors
mention that vegans had the highest intake in iron, about twice as high as the omnivore group, a finding that
was previously reported by two other studies57. Essentially the same results have been found in a 2015
dissertation in Germany, and the author suspected higher soy intakes of vegans to be the reason58. However,
based on the literature I reviewed it could also be explained by the above described inhibiting effects of dairy and
eggs on iron absorption. Looking at iron deficiency, as defined by a ferritin cut-off value of 15 μg/L, no
differences were found between the omnivore, vegetarian and vegan group57. This can be explained by a bigger
variance in the omnivore group on one hand, and previously discussed mechanisms on the other hand.
However, in this context a contradictory German study on 75 supposedly (as will be discussed later) vegan
women between 18 and 49 years of age has to be mentioned, where 40% were considered iron-deficient, a much
higher quota than the 10% which were said to be common for German pre-menopausal women 42. However, 32
of these 75 women were classified as ;<vegans, meaning that up to 5% of the ingested energy could be of
animal origin. As no use of animal products is the definition of genuine vegans, this group was effectively
vegetarian, and it is possible that this difference could have attributed to the result that lies in contrast to most
other studies, as a decreased iron status could be expected in this group. Unfortunately, while differences in
regard to iron intakes between vegetarians and vegans were published, this was not done in regard to actual
hematological status, which could have shed light on this hypothesis.
Iron deficiency is the most common nutritional deficiency in children. Globally 43% are affected. Still this
deficiency often gets overlooked, because symptoms are subtle and growth is not inhibited 50. Nonetheless,
prevention is important, because iron deficiency can have adverse effects on cognitive, emotional and behavioral
development, with other negative effects on immunity and cerebral vein thrombosis risk 50,59.
In the United States between 1999 and 2002, 9.2% of all children from one to three years of age were iron
deficient and 2.1% were suffering from iron deficiency anemia. This high incidence declined later in childhood
with only 1% of adolescent males being deficient. However, in adolescent and young adult females, 11% were
iron deficient and 2%-5% suffered from iron deficiency anemia60. Most likely, menstruation seems to be the
cause for this gender difference.
Iron deficiency in vegan children
Several studies show that vegan children exceed recommendations of iron intakes31, for example a longitudinal
study published in 1988, where vegan children showed mean iron intakes of 142% (range 108-200%)14.
However, only one study looked at the actual iron status of vegan children. It was a mixed group of vegan and
vegetarian children ranged 6 to 12 years and no difference compared to non-vegetarian children has been
found31. In a study of 44 vegetarian girls, including 2 vegan children, ranging from 11 to 14 years of age, no
differences were found between the vegetarian and the omnivore group in regard to iron deficiency anemia as
defined by a hemoglobin value below 120g/dl61. Because dairy and egg products, which are nutritionally the
main differences between vegetarian and vegan diets, contain very little iron, and even inhibit iron absorption
as discussed earlier, it can be argued that data from vegetarian children can be used for estimations, and
theoretically higher ferritin levels should be expected in vegan children, even though these ferritin levels should
have no influence on iron deficiency anemia.
To summarize, contrary to wide-spread belief, meat consumption does not seem to play a protective role from
iron deficiency, as no difference in prevalence has been found in studies of both adults and children, despite
lower ferritin levels. One explanation for this are adaptive mechanisms, allowing for habituation to low intakes
of iron, and habituation to (non-heme) plant iron. In cases of deficiency iron uptake can increase by a factor of
ten. Another explanation is the recent finding that plant ferritin, containing a significant amount of iron, can be
readily absorbed in the intestines. Larger studies on adults suggest that vegans have a higher ferritin levels than
vegetarians, most likely due to absence of the inhibiting influence of dairy and eggs on iron absorption. Iron
intake of vegan children seems sufficient, yet these findings have to be backed up by data on actual iron status of
vegan children, especially because multiple factors come into play when considering the comparative
bioavailability of plant iron and plant ferritin, respectively. Vitamin C can be a very effective agent for
improving iron status, as can be iron skillets or iron ingots. When looking at data from the general U.S.
population, it is expected that roughly 9% could be iron deficient in early life, with numbers rising to 11% in
adolescent females, leading to anemia in 5% of those cases as compared to only 1% in adolescent males. In this
thesis, hemoglobin, serum ferritin, and also serum soluble ferritin receptor (s-TfR) will be examined, because
the latter is not influenced by systemic inflammation62.
While calcium is readily available in plants, oxalate, phytate and dietary fiber can inhibit calcium absorption.
However, phytate content seems to be the main factor, as only high-phytate foods like spinach (5%) or rhubarb
(9%) fall significantly short of the absorption rate of cow's milk (32%), while phytate-poor foods like broccoli
(48%), kale (41%), bok choy (52%) exceed the absorption rate of cow's milk. Cereals were also reported to have
slightly higher calcium bioavailability than calcium from cow's milk. In the study that arrived at these numbers,
researchers used a summarized total calcium absorption rate of 24% in the vegan group63.
In general, calcium is readily available in vegan foods and beverages. Good vegan sources of calcium are
broccoli, Chinese cabbage, collards, kale, cereals, fruit juices, calcium-high mineral water (around 650 mg/L), as
well as fortified soy-milk or other plant milks. High-oxalate foods like nuts, dried beans and spinach have lower
bioavailability in regards to calcium64.
An English 1993 study on 38 vegans showed average intakes of 582 mg/day (SD=225) in men and 497 mg/day
(SD=236) in women65. A 1999 study on 25 U.S. American vegans showed a mean calcium intake of 710 mg/day
(SD=280) for females and 840 mg/day (SD=750) for males53. A German study on 98 vegans showed average
intakes of 915 mg/day (SD=346)66. A Swedish study on 30 vegans showed average intakes of 538 mg/day
(SD=350) in females and of 516 mg/day (SD=158) in males67. A Swiss study on 53 vegans measured average
intakes of 817 mg/day (SD=285). An Estimated Average Requirement of 800 mg/day was used in this study.
Compared to vegans, vegetarians and omnivores had significantly higher and adequate calcium intakes57. These
results show that while calcium intakes can be met on a vegan diet, there is usually a large proportion of
insufficient calcium intake among vegans. However an experimental study showed that, when attention to
calcium is given in the planning of a vegan diet, the calcium status can be adequate and lead to a positive calcium
balance. Notably, naturally calcium-rich mineral water was used to achieve a daily calcium intake of 843 mg/day
(SD=140), with mineral water providing up to 45% of the total calcium intake63. Similarly, a 1999 study on
vegans using supplements showed that average intakes of 710mg/day (SD=280) for females and 840mg/day
(SD=750) for males were reached.
The comprehensive EPIC-Oxford study68, confirmed these results. Vegans of the examined sample of 1126
participants aged 20-89 were in total over 30% more likely to suffer bone fractures than meat-eaters.
Vegetarians did not show any increased fracture risk. The same was true for 55.5% of all vegans. Those vegans
who did not meet the recommended calcium intake of 525mg/day (44.5%), showed an increased rate of bone
fractures. However, when interpreting these results in regard to generalizability it is important to note that a
significant amount of variables other than age and sex were adjusted for, with the bulk being lifestyle factors
that protect bone health in the vegan population. Vegans had the lowest BMI and were physically the most
active group (walking, cycling and vigorous exercise)68. Physical activity can have a large effect on bone health69.
A large longitudinal study over 21 years on 3262 healthy men demonstrated that the incidence of fractures was
reduced by as much as 62% in those performing intense physical activity69. Additionally, vegans scored lowest
for alcohol intake and smoking70, as is commonly observed in other studies71. Data on three prospective cohorts
with a total of 75'433 person-years suggests that while moderate alcohol consumption bears no increased
fracture risk, consumption of more than 2 units per day is increasing overall fracture risk by 23% and hip
fracture risk by 68%72. Furthermore, results from three meta-analyses showed that smoking is detrimental to
bone mass density and leads to an increase in overall fracture risk by 25% and an increase of hip fracture risk by
40-81%73. On the other hand, hormone replacement therapy (HRT) was used half as much in the vegan group,
and HRT has a significant positive effect on bone health, albeit it is mostly applied in post-menopausal women74.
By controlling for aforementioned lifestyle variables, it is factored out that the shown detrimental effects of a
low calcium intake on bone health could be partially, fully, or even overcompensated by named factors.
Unfortunately, the authors provided no unadjusted data to examine this effect70.
Unadjusted data is provided by a 2009 meta-analysis which found that while vegetarian and especially vegan
diets were associated with a lower bone mass density (BMD), the magnitude of the effect was deemed likely
clinically insignificant by the authors, meaning no increased fracture risk. Vegetarians scored 2% lower (95% CI:
1-4%.) while vegans scored 6% lower (95% CI: 2-9%) on BMD when compared to omnivores75. The authors
concluded that there is only a weak connection between calcium intake and bone health, and that other factors
play more dominant roles.
Regarding calcium intake, usually, 1000 mg/day, sometimes 800 mg/day are recommended for adults. However,
one study demonstrated that a positive balance, with the balance being defined as the calcium intakes minus
calcium excretion, was possible in 7 of 8 vegan test subjects (range: 27-252 mg/day) who had an average intake
of 843 mg/day (SD=140)63. Results discussed earlier showed a threshold for increased fracture rates at calcium
intakes of 525 mg/day68. These findings suggest the validity of the average requirement of 600 mg as it is e.g.
recommended by the Nordic Nutrition Recommendations67.
Overdosing calcium supplementation can be a health hazard. One study showed that calcium supplementation
of more than 1000 mg/day was associated with cardiovascular disease76. Another study showed that dietary,
non-supplementary, intake of calcium of 1400 mg/day was associated with higher cardiovascular risk77. Since
the intake of cow's milk was not controlled for, it is unknown if this effect was due to calcium itself or to other
ingredients of milk and dairy.
To make the bridge to children, it has been shown as early as 1969 that children can reach a positive calcium
balance with intakes as low as 200 mg/day in 28 Indian children of 3 to 5 years78. However, other researchers
argued that these results cannot be applied unmodified to other ethnic groups, as Indians have a lower peak
bone mass when compared to Caucasians, for example79. Furthermore, in 2002 researchers concluded that a low
calcium intake does not have any deleterious effect on bone health of young individuals. There is a hypothesis
that calcium deficiency could affect bone fragility in adolescents, but supporting definitive data was still lacking
at this point79.
In a longitudinal study published in 1988, vegan children had only 52% (range 28-85%) of recommended
calcium intakes. In accordance with studies presented above, growth was nonetheless normal across the whole
group14. Still, calcium deficiency during childhood may affect peak bone mass, most of which is accumulated at
the age of 18 years, and which is predicting fractures at old age 79. As of 2011, U.S. recommendations for calcium
intake are 700 mg for children 1-3 years to 1000 mg/day for children 4-8 years to up to 1300 mg for children
between 9 and 18 years of age80. Calcium balance studies suggest an intake of 1500 mg/day for adolescents,
depending on body height and physical activity79.
To summarize, despite good sources for calcium in both vegetables and fortified foods and drinks, vegans have
on average merely half the calcium intake of omnivores, which holds true for both adults and children. There is
evidence that achieving a positive calcium balance in children can be reached with low intakes, and low calcium
intakes of vegan children does not affect growth. Calcium intake has a clinically insignificant to small impact on
peak bone mass density. However, when protective lifestyle factors are factored out, it was shown that a large
proportion of vegans not meeting recommended calcium intakes (44.5% in the studied sample) had a 30 percent
higher risk for bone fractures. In this thesis, we will examine serum calcium levels as well as fractures rates,
because in children of the general population who were avoiding milk, higher rates have been observed81.
220.127.116.11 Vitamin D
Vitamin D is an important regulator of calcium and phosphate metabolism. It has been suggested that it might
play a role in neurophysiological functioning and cancer prevention. In children, vitamin D is discussed to play a
role in asthma, type 1 diabetes mellitus, infectious diseases such as respiratory infections and influenza, as well as
For light-skinned children living in a moderate climate, the exposition of face and hands for 20 to 30 minutes to
the sun 2 to 3 times per week will generate enough vitamin D to meet recommended levels. Sun-exposure needs
to be increased or can be insufficient in children with darker skin or living in cloudier or more northern
Fatty fish and in a smaller order egg yolk and certain fungi are dietary sources of vitamin D, while breakfast
cereals, fruit juices, margarine as well as different kind of dairy products and cow's or plant milk are sometimes
fortified with this vitamin82. Vitamin D is stored in the fatty tissue82 and it readily crosses the placenta.
Therefore the status of the fetus depends on the mother50. Because approximately 90% of vitamin D is sunlight
derived83, dietary vitamin D plays a minor role for vitamin D status, unless it is being used to compensate with
supplements for insufficient endogenous synthesis in the skin due to genetic predisposition or low sunlight
Despite vitamin D being the second most common deficiency in children (rickets), it often gets overlooked
because it is mostly asymptomatic and growth is not inhibited 50. Symptoms that could occur are craniotabes
(softening or thinning of the skull in infants and children), genu varum or valgum, costochondral swellings,
growth delay or arrest, muscle weakness, hair loss or alopecia, refusal to walk, fractures, seizures or tetany84. In
adults, deficiency leads to osteomalacia and has been associated with cardiovascular disease, insulin resistance
and hypertension50, as well as impairment of basic and executive cognitive functioning, depression, bipolar
disorder, and schizophrenia85.
In the United States up to 14% of the general population are affected by vitamin D deficiency. Human milk (25
IU/liter) as well as fortified formula typically fail to provide the 200 to 400 IU/day infants and young children
need and this cannot always be compensated with sunlight exposition, especially when children have dark skin
and the climate is not optimal for sun exposure. Among children, those ranging from age 1 to 5 were reported
to have the highest vitamin D levels. Throughout childhood, these levels decrease, with adolescents scoring
A 2005 Swiss study of 206 adults ranging from 18-50 found that vegans had a only marginally yet significantly
lower daily dietary intake of vitamin D (median 0.1 μg) when compared to vegetarians (median 1.2 μg) and
omnivores (median 1.1 μg). To put these results into perspective, almost no one in any group did meet
recommended estimated average requirements of 10 μg per day57.
The larger EPIC Oxford study conducted in 2002 on 65'429 men and women aged 20 to 97 years reported that
vegans had a mean intake of 0.88 μg/day with corresponding values in the vegetarian group of 1.57 μg/day and
3.39 μg/day in the omnivore group70.
A smaller Finnish study on 6 vegans, 6 vegetarians and 16 omnivores conducted in 2001 showed lower vitamin
D intake of vegans of 0.09 μg/d (SD = 0.06), as compared to lactovegetarians (0.7 μg/d; SD = 0.4) and omnivores
(4.0 μg/d; SD = 2.1). Vegans also showed significantly lower plasma vitamin D levels in both winters assessed,
but not during summer. Interestingly the bone mineral density (BMD) was also assessed. A tendency for lower
values in the vegan group yet no statistically significant difference was found, which might be due to the low
sample size.86 To re-iterate from the sub-chapter on calcium, a 2009 meta-analysis found that while vegetarian
and especially vegan diets were associated with a lower BMD, the magnitude was likely clinically insignificant.
Vegetarians scored 2% lower (95% CI: 1-4%.) while vegans scored 6% lower (95% CI: 2-9%) than omnivores75.
Another EPIC-Oxford study conducted in 2010 on 2107 white men and women located in the United Kingdom
assessed that the degree of animal product exclusion positively correlated with low vitamin D intake and status.
Vegans (n=87) showed an average intake of 0.7 μg/d (SD = 0.6-0.8), whereas vegetarians and omnivores had
significantly (p<0.05) higher average intakes of 1.2 μg/d (SD = 1.1-1.3) and 3.1 μg/d (SD = 3.0-3.2), respectively.
Serum 25-hydroxyvitamin D (25(OH)D) concentrations were 55.8 nmol/L (95% CI: 51.0-61.0) for vegans
(n=89), significantly (p<0.05) lower when compared to 66.0 nmol/L (95% CI: 63.3-68.8) in vegetarians and 77.7
nmol/L (95% CI: 75.4-78.8) in omnivores. Supplement-users had mean plasma concentrations of 78.1 nmol/L
(95% CI: 76.3-80.0). Seasonality had a considerable effect A )B Because vegans rely more on endogenous
synthesis, they showed the largest differences in plasma concentrations between summer and winter. The
authors concluded that sun exposure has a larger effect on vitamin D status than the dietary intake. An example
for this is the average concentration of vitamin D in vegans in summer being higher than the average
concentration in omnivores in winter87. Unfortunately, methodological and technical issues are preventing
direct comparison of serum concentrations across laboratories and no clear-cut lower limits for the lower range
are available. When looking at minimized serum parathyroid hormone levels, as a marker for vitamin D
deficiency, vitamin D concentrations ranging from 5 to 80 nmol/L can be normal, so results have to be
interpreted within the clinical context of each patient88. When comparing seasonal plasma vitamin D levels
between the dietary groups in the aforementioned study, 45% (summer) respectively 20% (winter) of vegans,
56% (summer) respectively 37% (winter) of vegetarians and 65% (summer) respectively 40% (winter) of
omnivores had plasma concentrations equal or above 75 nmol/L87, that is to say in a range where one can safely
assume sufficiency. In a current Finnish sample of 21 adults who were vegan for an average of 8.6 years (range:
2-16), 68% were supplementing vitamin D, resulting in median levels of 54 nmol/L (range: 49-69), which is
sufficient in regard to a reference range of 50-75 nmol/L89.
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AF3F3 F 3 F B87
When looking at vitamin D status of adolescents, the 2014 HELENA (Healthy Lifestyle in Europe by Nutrition
in Adolescence) cross-sectional study on 3528 adolescents ranged 12.5-13.5 years, 75% had insufficient plasma
vitamin D concentrations (50-75 nmol/L), while 15% had deficient concentrations (27.5-49.99 nmol/L)90. The
difference between deficient and insufficient, as defined in the cited study, is that on below the cut-off from
sufficiency to insufficiency (75 nmol/L), parathyroid hormone (PTH) is increasingly secreted by the parathyroid
glands as a counter regulatory mechanism. However, this cut-off is controversial, as this increase varies
individually and can start as low as 45 nmol/L, as cited in this study, or as low as 5 nmol/L, as other sources on
adults have cited88. The cut-off for deficiency defines the point at which serum vitamin D and calcium
absorption declines significantly, but as this deficiency is a consequence of aforementioned insufficiency, much
individual variation of this cut-off can be expected. In 2010, experts in the field deemed the multitude of almost
synonymous terms such as ;<, ;<and ;>< confusing, especially because their cut-
offs could all vary, depending on the publication. However, they stated that recently an optimum concentration
of >30 ng/ml (75 nmol/L) has been determined, because favorable health-outcomes occur in ranges of 36-50
ng/ml, with ≤ 20 ng/ml (50 nmol/L) becoming widely accepted as a standard definition of vitamin D deficiency
across the age spectrum84. Interestingly, female adolescents where at a higher risk for deficiency than their male
counterparts84. Further, in both children and adolescents, an inverse correlation between total body fat and
vitamin D has been found, most likely due to the fat-soluble basis of this vitamin leading to less bio-
As large doses of dietary vitamin D are mostly available in fortified foods, both non-vegan and vegan children
concerned should be advised to consume them31,82. However, it is controversial if vitamin D supplementation
other than fortification should be advised for all children regardless of risk factors82.
Vitamin D2 is the common vegan alternative to the usually wool-derived and therefore non-vegan vitamin D3.
Vitamin D2 is substantially less bioavailable, which means that intakes must be higher by a factor of 1.7, or that
specifically produced vegan vitamin D3 should be used instead91.
There is only one study that examined vitamin D supplementation in vegan children. A longitudinal study
published in 1988 stated that [sic!] vegan parents were aware of the importance of exposing their children
to sunlight, especially during winter, and [sic!] of them were using vitamin D supplements14.
Unfortunately, data on vitamin D status in vegan children is unavailable to date.
Depending on chosen average cut-off points, vitamin D deficiency is generally considered a widespread problem
among all age groups. Dietary intakes of vitamin D are considerably lower among vegans, although no
detrimental effect of these decreased levels on BMD could be shown. Cut-offs for vitamin plasma levels seem to
vary significantly among individuals, and technical inconsistencies during measurement impair the
comparability between results generated by different laboratories. Lacking sunlight seems to play the dominant
primary role regarding vitamin D status, usually providing 90% of the demand. Nonetheless, aside from more
sun-exposure, deficiency can be addressed with higher dietary vitamin D intake using supplements. When using
vitamin D2, the dosage has to be adjusted due to inferior bio-availability. No data on vitamin D plasma levels of
vegan children is available as of yet.
18.104.22.168 Cobalamin (Vitamin B12)
Cobalamin is an evolutionary ancient molecule which acts as a cofactor in prokaryotic as well as eukaryotic
metabolism, functioning originally in the support of fermentation of small molecules in early emerging biotic
processes. As the atmospheric levels of oxygen changed in early times, cobalamin developed secondary functions
such as methyl transfer or nucleotide reduction92. In humans, large amounts (5 μg/24h) of cobalamin are
produced by bacteria in the colon, but as the terminal ileum would be the location for its uptake, it is excreted.
In one remarkable study, a researcher treated vegan volunteers with cobalamin deficiency and megaloblastic
anemia with dietary water extracts from their own stools, thereby curing them93. In the 1980s, the enteric
bacteria ! and G have been shown to synthesize cobalamin de-novo
under anaerobic conditions, and later it was confirmed that most enteric bacteria were able to synthesize
cobalamin under both anaerobic and aerobic conditions93,94.
There is a small amount of these bacteria in the small intestines with an increasing quantity towards the
ceacum93. Even though the minimal daily requirement of around 0.1 μg 93, it is unknown whether they could
produce enough – epidemiological evidence discussed later suggests that for most people this is certainly not the
case. The regular pathway for cobalamin absorption would require binding to the intrinsic factor in order to be
absorbed as a complex in the terminal ileum. One author deemed it unlikely that cobalamin produced by bacteria
in the small intestines could be absorbed, for this reason95. However, from my understanding, cobalamin could
theoretically bind to intrinsic factor in the small intestine and then be absorbed. Be that as it may, even if
sufficient amounts are provided through this pathway, this production could be compromised by a shift in the
flora, be it through disease or other factors. Indeed, bacterial overgrowth in the small intestine has been
commonly associated with cobalamin deficiency, as bacteria use cobalamin for themselves96. It is problematic
that presented findings on endogenous cobalamin production are used by advocates of raw diets to claim that no
cobalamin supplementation is needed.
Cobalamin (vitamin b12) is mostly absent in unfortified plant food. Known exceptions are certain algae, such as
Spirulina or Chlorella. Examined Spirulina tablets contained for the most part (83%) cobalamin analogues
(which have no nutritional value to humans), but also a small fraction (17%) of real cobalamin97. This
composition has lead previous researchers to suspect that Spirulina contain no bioactive cobalamin at all98. A
most recent study has found around 40 μg cobalamin per 100 g of biomass99. More recently, two samples of
Chlorella algae were analyzed confirming contents of 19 and 38 μg of cyano-cobalamin per 100g100, making both
algae a comparable cobalamin source for vegans although with caveats. Firstly, it appears that cobalamin
concentrations can vary significantly, mandating regular testing of production batches or cobalamin status of the
consumer, secondly, supplementing cobalamin with algae is disproportionately more expensive than using
cobalamin variants that were biochemically produced and come in the form of tablets or sprays, which cost
between $15 and $40 per year.
Because the synthesis of cobalamin is highly complex (taking 70 steps) this method is technically too challenging
and too expensive to be chemically produced, and genetically optimized microorganisms conducting
fermentation are utilized instead. UV light or other mutagens are used to provoke random mutations, and the
most productive bacterial strains are selected92. Supplementation with either biochemically produced cobalamin
in the form of pills or fortified foods or with Spirulina or Chlorella algae can be seen as an integral part of a
standard vegan diet, as discussed in the introduction. When substituting orally, high-doses (1000 to 2000 μg)
should be used to ensure that at least 1% of the dose enters the blood stream by mass action in the possible
absence of intrinsic factor101. Due to cobalamin being a water-soluble vitamin, overdosing has not been
reported64. In certain cases of parenteral high-dose supplementation with methyl-cobalamin acne has been
reported, but it is unclear if this was due to iodine particles in the used preparations 101. Vegans using false,
insufficient or no cobalamin supplements or fortified food/drinks at all, are thought to inevitably run low, until
a deficiency develops. Cobalamin stores can last several years to deplete, typically at least three101, which can lead
some vegans to the wrong conclusion that their needs are met.
The standard screening test for is measurement of total plasma cobalamin. Studies indicate that measurement of
holoTC, plasma cobalamin bound to transcobalamin, has equal diagnostic accuracy. Early noticeable symptoms
of cobalamin deficiency are unusual fatigue, digestion problems, and frequent upper respiratory infections 102.
More distinguished deficiencies are marked by growth and movement related disruptions, developmental
delays, and hematologic abnormalities. Neurological symptoms encompass paresthesias, numbness, weakness,
loss of dexterity, impaired memory, and personality changes. Those abnormalities can develop in the absence of
pathological red cell anomalies, as a primary consequence of cobalamin deficiency. An association with auto-
immune disease in older children and adolescents was described, such as polyglandular autoimmune syndrome,
Hashimoto thyroiditis and pernicious anemia. Physical abnormalities can be avoided if deficiency is identified
early on 50. A deficiency can also be a risk factor for CVD 103. Deficient levels of cobalamin are below 147 pmol/L
or 200 pg/ml96. Usually the Recommended Daily Allowance (RDA) is 1 μg/24h, however, the minimum daily
requirement seems to be as low as 0.1 μg, as this dose has shown to lead to a slow but measurable replenishing of
Vegans have usually been shown to have the lowest cobalamin levels when compared to vegetarians and
omnivores102, a fact that is most likely due to insufficient or absent substitution or consumption of fortified
foods or drinks. In the 2010 British EPIC-Oxford study, on 689 men, vegans had average levels of 122 pmol/L
(95% CI: 117-127), resulting in a deficiency (<118 pmol/L) of 52% in vegans. In the vegetarian group, 7% were
deficient in cobalamin. Curiously, supplementation of cobalamin made no difference on serum concentration101.
In a more recent, 2015 Swiss study of 206 adults ranging from 18-50, there was surprisingly no significant
difference in medium cobalamin status or cobalamin deficiency between omnivores, vegetarians and vegans.
This could be attributed to only recent adoption of a vegan diet (averaged 1-3 years in the Swiss study compared
to 7 years in the aforementioned EPIC-Oxford study), to sex (mixed group in the Swiss study compared to the
exclusively male group in the EPIC-Oxford study), exclusion of the chronically ill in the Swiss study,
participation bias or a different make-up of the overall Swiss vegan population or its diet. In the Swiss study,
43% of the vegan sample regularly used cobalamin supplements, but researchers did not assess dose or
frequency. When vegans not using supplements were analyzed separately, they had only a mildly lower status
(274 pmol/L vs. 342 pmol/L; cut-off for deficiency = 150 pmol/L), which was explained by the endogenous
stores which can take years to deplete. On average vegans had been following their diets for 1-3 years. Other
reasons could be the irregular use of supplements or the use of fortified foods or drinks 57, or different extents of
endogenous synthesis. In a 1999 U.S. American study on 25 vegans, 36% were using B12 supplements53. In a
2002 Swedish study on 30 vegans, 37% of all vegans used cobalamin supplements67. In the 2010 EPIC-Oxford
study on 232 British vegan men, 19% used supplements regularily104. From these studies, it can be estimated that
only a third to half of the vegan population is using supplements, with no guarantee that those supplementing
are doing so with sufficient concentration and consistency. It could be hypothesized that supplementation rates
have improved slightly through time in existing vegans or are slightly higher in the large amount of people
having adopted a vegan diet in more recent years. In the 2016 Finnish study on 22 vegans who were vegan for
an average of 8.6 years (range: 2-16), 73% were supplementing cobalamin and as expected adequate median
plasma levels of 328 pmol/L (238, 474) were observed (reference value: >150 pmol/L)89.
A 2000 study on 49 subjects who had been following the raw vegan Hallelujah diet for 23-49 months found 12%
to be insufficient (plasma concentration < 147 pmol/L) in cobalamin and 76% having below-normal cobalamin
levels of < 221 pmol/L. Only participants using no cobalamin supplementation were selected in this study.
Interestingly, length of time following this diet did not correlate with cobalamin levels96, which would suggest
factors other than internal stores were playing a role. In this study a maximum of 24% have sufficient amounts
of endogenous synthesis.
A 2005 study on 201 Germans who adhered to a raw diet for a median duration of 3.5 years found that 38%
were cobalamin deficient, with cobalamin status decreasing according to the type of raw food diet in the
overwhelming majority that was not supplementing cobalamin (94%). Cobalamin supplementation was used
only by 12 individuals. Regarding faw food types, 58% were omnivores including meat and fish, 21% were raw
lacto-ovo-vegetarians and another 21% raw vegan. Vegans had the lowest cobalamin status (126.2 pmol/L; CI =
87.8-182.2), with lacto-ovo-vegetarians scoring higher (143.2 pmol/L; CI = 121.2-175.9) and omnivores scoring
highest (174.5 pmol/L; CI = 142.2-249.8). Compared to the omnivore group, ovo-lacto-vegetarians had an
odds-ratio of 3.1 and vegans an odds-ratio of 5.4 for being deficient in cobalamin. The majority (75%) of
participants adhered rather strictly to the raw diet, with >90% of their intake being raw105.
As discussed above, endogenous biosynthesis cannot be considered a trusted method for securing cobalamin
supply, even more so for vegan risk sub-populations such as pregnant women or children. However, it cannot
be ruled out that for few individuals, it is possible to produce sufficient amounts of cobalamin with bacteria in
the small intestines, because there are studies where cobalamin supplementation played no or only a small role
in explaining cobalamin status57,101. In one study on not supplementing raw vegans the duration of the vegan diet
did not correlate with cobalamin status, suggesting that as much as 24% could sustain sufficient levels of
cobalamin despite no supplementation96. To clarify this issue, more research would be needed. In any case, these
results and the possible real-life exceptions can be detrimental to the efforts of convincing vegans to supplement
cobalamin. This is aggravated by a delay in deficiency due to internal cobalamin stores101, which can further
It is estimated that infants aged 0-6 months require 0.4 μg/day of cobalamin and those 6 to 12 months 0.5
μg/day, respectively. These requirements are usually met if the mother is not cobalamin deficient 101, but studies
show that even among breast fed omnivores, supplementation can be indicated106. Cited authors recommend an
RDA of 0.9 μg / day for children aged 0 to 3 years, 1.2 μg/day for children aged 4-8 years, 1.8 μg/day for
children aged 9-13 years, and 2.4 μg/day for youths aged 14-18 years. To secure sufficient intakes, it is
recommended that vegan children get three servings of fortified foods or drinks or alternatively take daily
supplements of 5 to 10 μg of cobalamin107.
There is sparse data on parental awareness regarding cobalamin supplementation for their children. A
longitudinal study published in 1988 showed that ;“ (no percentage was provided by the authors) examined
vegan parents were aware of the importance of cobalamin substitution14. Furthermore, most of those children
had sufficient intakes of cobalamin (mean 280% of the recommended daily amount; range 20-1695%)14.
Unfortunately, because no standard deviation was provided, it is impossible to calculate a percentage of
adequately supplied children in this study.
One year later, in 1989, a study performed in a collective community in Tennessee, USA, called ;1<,
showed that of 348 children, 75% were on a vegan diet, because from its founding days in 1971 until 1983, the
whole population was on a vegan diet. Of the entire population, 76% used vitamin/mineral supplementation
which was added to their self-made plant milk and 78% used nutritional yeast (believed to naturally contain
cobalamin, which is indeed not the case) supplementation108,109. When only looking at the vegan children, this
number might be even higher, but the authors did not provide this information.
Prevalence of childhood and adolescence cobalamin deficiency is unknown. The NHANES III study (1991-1994)
estimated that 0.5% of all children aged 4 to 19 have levels of cobalamin below 200pg/mL50. In the 2014
HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) cross-sectional study of 3528 adolescents
ranged 12.5-13.5 years, the median value of the 1051 blood-sampled subjects was 319 pmol/L, with a range of
110-1091 (cited cut-off for deficiency < 149 pmol/L)90.
Maternal cobalamin deficiency during pregnancy can lead to neonatal cobalamin deficiency 110. Because
cobalamin is actively transported via the placenta, pregnancy can cause cobalamin deficiency in pregnant
women111. In the literature, there is a case report of a maternal vegan diet causing infantile neurological disorder
due to cobalamin deficiency111. Notably, the parents refused any ;<, such as vaccinations or
pharmaceutical products. After birth, It is unclear whether or not maternal cobalamin stores are accessible to
infants via breast milk30. Since only case reports could be found, there is no reliable data on cobalamin deficiency
among vegan newborns and infants.
Regarding children, a study published in 2006 showed significantly lower cobalamin status in a mixed group of
vegetarian and vegan children ranged 2-10 years. Only 5 of 32 children were vegan. 4 of the 27 vegetarian
children (15%) averaged cobalamin intakes below the recommended 1 μg/day, while all 5 of the vegan children
didn't meet recommended cobalamin intakes112. Because too few vegan children were analyzed, and non-
published confidence intervals might overlap with the RDA cut-off, these numbers are weak evidence and
warrant further investigation. The study also demonstrated that cobalamin deficiency among vegetarian
children can be a significant problem, even though it confirmed previous findings that vegetarians can obtain
cobalamin from dairy and eggs if consumed regularly 64,107.
There is further limited evidence from a study on 48 preschool children aged 2-5 years who were fed a vegan
diet from birth on. Parents used cobalamin fortified soy milk as well as fortified nutritional yeast. Even though
no blood parameters are available, no cases of overt cobalamin deficiency were reported109.
The metabolic pathways of cobalamin are often connected to folate. This has crucial consequences. Cobalamin
deficiency can be partially masked by high folate levels64. This is especially likely in vegans, who, as will be
shown in the next chapter, have considerably better folate status than omnivores. In such a case, folate will
prevent hematological symptoms to occur, while allowing other symptoms due to inflicted neurological damage,
which can be irreversible. In effect, this could lead to isolated neuro-psychiatric disorders to occur, which can be
harder to detect and to match to the correct etiology.
To summarize, low cobalamin levels and cobalamin deficiency have a high prevalence in vegan populations,
even though it cannot be excluded that few individuals have sufficient endogenous synthesis. The main reason
for this wide-spread problem is the low rate of supplementation, estimated at around 40%. There is tentative
evidence that the awareness for supplementation is much higher among newer vegans and in vegan parents in
regard of their children. In one instance at least 78% of all children received supplements, but this number is
from a collective community in the 1970ies and 1980ies, and might not be representative for today's general
vegan population. From this population, we also have the only data on cobalamin status in vegan children.
Therefore there is an urgent need for further investigation on both the prevalence of cobalamin deficiency and
motivations leading parents to avoid supplementation of their children. Furthermore, monitoring blood levels
of cobalamin is indicated regarding vegan children, and in case no such monitoring is being undertaken, being
watchful of neurological or neuro-psychiatric symptoms.
22.214.171.124 Folate / Folic acid
Folic acid is mostly available in plant foods such as yeast, germs, pulses, bran, sprouts, green vegetables, nuts but
also in liver, since this is the organ used in mammals for internal storage57.
Because of wide-spread folate deficiency in the general population, especially in omnivores, women capable of
becoming pregnant, even those without an intention to do so, are advised to consume a total of 400 μg/d of
folate113. One reason is the modest association between maternal folate concentration in early pregnancy and
head growth114. Another is the association between folate deficiency and neural tube defects such as spina bifida,
anencephaly and encephalocele101,115. During pregnancy and lactation, folate requirements increase to 500-800
μg/d50. Compared to cobalamin deficiency, folate deficiency affects blood parameters similarly (megaloblastic
anemia, decreased leucocyte count, increased serum iron, evidence of mild hemolysis, decreased serum
haptoglobin, elevated lactate dehydrogenase, slightly elevated unconjugated bilirubin) but no neurological
deficits are known50. There is preliminary evidence that folate deficiency, promotes vascular disease and
cancer101. Also, folate stores are significantly smaller (5-10 μg) than the stores for cobalamin, and therefore a
folate-deficient diet can lead to megaloblastic anemia within only 4-5 months50, as opposed to several years in
the case of cobalamin101.
For children aged 9-13 years the estimated average requirement (EAR) is 250 μg/d irrespective of gender,
increasing to 330 μg/d for adolescents ranging from 14 to 18 years116.
As a public-health intervention, the U.S. food and drug administration (FDA) has required the fortification of
enriched cereal-grain products with folic acid, with a resulting increase in folate levels across all ages, sexes and
ethniticies50. It seems that fortification of foods with folate is a potential solution to this widespread deficiency.
In Germany, the intakes of fortified foods doubled between 1987 and 1995 (from 8-19% to 20-32%) 116. However,
described amounts of supplementation still fall drastically short of recommendations. In the German DONALDS
(Dortmund National Anthropometric Longitudinal Design Study) study it was reported that between 1985 and
2000 folate fortified foods accounted for 10-15%, while non-fortified foods provided 20-30% of recommended
intakes. This suggests that fortified foods provided 33-75% of total intake, which in this case was still below
recommendations in 55-70% of children aged 5 to 18117. A 2006 review on all available data on European
adolescents reported that folate intakes were typically 50-66% below the estimated average requirements (EAR),
without any clear geographical tendencies. Researchers suggested a strong need for further investigations116.
The 2014 HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) cross-sectional study of 3528
German adolescents ranged 12.5-18.5 years, 35% of the 1051 blood-sampled subjects had insufficient plasma
folate (10.2-13-5 nmol/L; 4.5 μg/L), while 15% had deficient plasma folate (<10.2 nmol/L; <4.5 μg/L). This is
consistent with the finding that only half of the recommended amounts of fruits and vegetables were consumed
in this sample 90. Interestingly, almost 30 years earlier, the DONALDS (Dortmund National Anthropometric
Longitudinal Design Study) study, assessed as well that only 50% of German children aged 4-18 years ate
recommended amounts of vegetables and the same being true for fruits, unless fruit juice was added to this
A recent Swiss study of 206 adults ranging from 18-50 years showed that vegans scored significantly higher in
regard to median folate when compared to either vegetarians or omnivores. 58% of all omnivores were deficient
in folic acid, as compared to 30.2% in vegetarians and 13% in vegans, a result that is in accordance with previous
A study conducted in 2006 showed a significantly higher folate status (even surpassing allowances) in vegan
children ranged 2-10 years when compared to vegetarian and omnivore children. However, since only 5
children were analyzed and no confidence intervals were provided, the evidence is weak112.
It can be estimated that among omnivores around 35% of all children have insufficient plasma folate levels and
15% are deficient, a problem which is more pronounced in adulthood, where up to 58% are deficient. The
relative risk of vegan adults developing folate deficiency can be estimated to be smaller by a factor of four. While
data on plasma levels of vegan children is sparse (n=5), it could be expected that folate deficiency is rare within
this group. To much surprise, no serum folate levels were assessed in the extensive KiGGS dataset. To
compensate, homocysteine will be used, as it increases in the absence of folate, for it cannot be converted to
methionine. Further, markers for megaloblastic anemia will be used, namely hemoglobin and MCV.
Vegan diet has a higher content of potassium119. To be more precise, the EPIC Oxford study conducted in 2002
on 65'429 men and women aged 20 to 97 years showed that compared to vegetarians, pescitarians and
omnivores, vegans had a slightly higher intake (<5%) in potassium. No evidence on potassium status could be
found regarding vegan children or adolescents, but there is no reason to assume that potassium status is
Vegan diet is high in magnesium119, as it is contained in green vegetables, nuts, seeds and beans. The EPIC
Oxford study conducted in 2002 on 65'429 men and women aged 20 to 97 years showed that compared to
vegetarians, pescitarians and omnivores, vegans had the highest intakes of magnesium70. No evidence on
magnesium status could be found regarding vegan children or adolescents, but physiological levels can be
126.96.36.199 Weight and Height
Increasing prevalence of pediatric overweight and obesity has spread from industrialized societies to urban areas
of developing countries. As of 2010, it was estimated that 1 in 10 children are overweight or obese worldwide
and 1 in 3 in the United States. Overweight promotes other diseases, including type 2 diabetes, which is on the
rise in children and adolescents120. Overweight children and adolescents have unfavourable blood lipids and
insulin and increased blood pressure, leading to early onsets of atherosclerosis 121. Unfortunately, both increased
weight during young years and associated risk factors have a strong tendency to stay. Obesity at age 6 has a 50%
chance of persisting into adulthood and obesity in adolescence even 70-80%120.
" . . 3
The EPIC Oxford study published in 2003 on 37'875 individuals aged 20 to 97 years showed that the body-mass-
index (BMI) and obesity rates were lowest in vegans, followed by vegetarians and omnivores. Males were on
average 6 kg and females on average 5 kg lighter than omnivores. Interestingly, smoking and exercise explained
only 5% of the difference, the rest was likely explained by dietary factors. Looking at food composition, protein
(as percent of energy intake) and fiber were the most important determinants of BMI, with vegans consuming
the least protein and the most fiber122.
For proper growth, energy intake is a crucial determinant, and studies on vegan children showed that energy
intakes are close to or up to par with omnivore controls109. In 1988 a long-term study beginning in 1968 on 39
British vegan children was published. These children were not brought up in communes and their parents
tended to be well educated and receptive to dietary advice. Authors reported that height, weights and head and
chest circumferences were inside the normal range for almost all children. One child showed signs of
malnutrition at age 13 months, but caught up at the next examination when she was 8 years old. Unfortunately,
no statistical analyses regarding variables related to growth were undertaken14.
Data on a collective community, ;1<assessed in 1989 on 404 children between the age of 4 months and
10 years, 75% of which were vegan, showed that these children showed no evidence of marked abnormality in
regard to body height or weight. There were statistically significant yet small differences at ages 5 years and
younger which were most pronounced between the ages 1 and 3 years (-2.01 cm), but these were suspected to be
related to limitations of the growth reference used. Regarding weight, no differences were found in birth
weight, but vegetarian children were significantly lighter at the ages 9 and 10 years (-1.1 kg)108.
There is evidence that consumption of plant based food is associated with lower BMI not only in adults, but also
in children, because different animal products have been shown to promote childhood obesity. Consuming large
quantities of animal protein, especially via dairy products, during the age of 12-24 months has been shown to
increase BMI and body fat at age of 7 years123. A population-based prospective cohort study of 2'922 children
looked at the impact of nutrition in early childhood on body composition at six years of age. Low intakes of folic
acid, a nutrient overwhelmingly found in plant-based foods, predicted high BMI. High intakes of methionine
through meat, fish and eggs, not only predicted high BMI, but also higher body fat percentage. Interestingly, this
was true independent of total protein intake124.
While growth of vegan children seems to be within a healthy range, statistically non-significant differences
point into the direction that they have a tendency to be smaller in statue. Other evidence shows that meat, fish,
eggs and especially dairy predicted high BMI and low folic acid predicted high BMI, with vegan children being
lighter than their omnivore peers. Researchers have suggested that vegetarian diets could be an effective tool to
combat increasing prevalence child overweight and obesity and its ramifications120. We will therefore assess
body height, body weight and the body-mass-index (BMI) [kg/m²]. Animal proteins, especially dairy products
might play a key role in the described differences, and the next sub-chapter will examine the role of dairy more
When comparing vegan children to vegetarian and omnivore children, new evidence on the various effects of
the consumption of cow's milk should be discussedThe advantages of cow's milk are widely known and will be
stated first. Afterwards, considerably less known findings will be presented.
Advantages of cow's milk The main advantage is its nutritional diversity. The average cow's milk is
composed of 87% water, 4-5% lactose, 3% protein, 3-4% fat and 0.8% minerals and 0.1% vitamins125. The
insoluble fraction, caseins, amount for 80%, while the remaining 20% are the soluble whey proteins. These
proteins have a high amount of essential amino-acids and good digestibility for humans. Milk proteins and
peptides resulting from their hydrolysis exert biological functions in the human body that could be beneficial.
These actions are antibacterial, antiviral, antifungal, antioxidant, antihypertensive, antimicrobial,
antithrombotic, opioid and immunomodulatory roles, as well as improving absorption of some nutrients125. Of
the fatty acids contained in milk, 98% is triacylglycerol (TAG), 2% diacylglycerol, <0.5% cholesterol, ~1%
phospholipids and 0.1% free fatty acids. The saturated fatty acid (SFA) content is 70%, whereas 30% of the fats
are unsaturated. Milk contains the vitamins A (50-1720 μg/L), D (5-35 IU/L) and E, former depending on fat
content, as well as riboflavin (1600-1700 μg/L; 1 cup supplying 38% of the DRI (dietary reference intake)),
thiamin (400-500 μg/L; 1 cup supplying 10% of the DRI), niacin (800-900 μg/L; 1 cup supplying 1.8% of the
DRI), piridoxin (400 μg/L; 1 cup supplying 8.5% of the DRI), folate (51 μg/L; 1 cup supplying 3.9% of the DRI),
and cobalamin (3500-5000 μg/L; 1 cup supplying 49% of the DRI). Most distinguished in milk is its rich calcium
content (1215 mg/L; 1 cup supplying 38.5% of the DRI), followed by parts of phosphrous (970 mg/L; 1 cup
supplying 24% of the DRI), magnesium (125 mg/L; 1 cup supplying 9% of the DRI), potassium (1485 mg/L; 1
cup supplying 8.5% of the DRI), zinc (5 mg/L; 1 cup supplying 11.5% of the DRI) and selenium125.
Growth and different IGF-1 levels for dietary groups A 2006 review126 has concluded that consumption of
cow's milk increases IGF-I, which in turn stimulates linear growth, which is not only true for populations in
developing countries, but notably also for well-nourished populations in industrialized countries127.
A British study published in 2000 on 223 vegan men, 237 vegetarians and 226 omnivores found vegans' mean
serum IGF-1 to be 8% less than vegetarians (p>0.05) and 9% less than omnivores (p>0.05)128. A 2002 study on
292 British women, 92 of whom were vegan, similarly showed that vegans had 13% lower levels of circulating
IGF-1 when compared to the their vegetarian and omnivore peers129. Other authors reported that high milk
consumption resulted in a 10% increase of circulating IGF-1 in adults and a 20-30% increase of circulating IGF-
1 in children126. Consistent with these findings, Mongolian children 10 to 11 years of age who were not used to
milk consumption were given 710 ml whole milk every day for one month. Four weeks later, their circulating
IGF-1 levels were still raised by 23.3%. The described effect of milk on IGF-1 seems to be triggered by its casein
protein fraction126. Milk consumption leads to a higher birth height as well as more rapid linear growth during
childhood. The Growing Up Today study, including 9'039 girls and 7'843 boys, all offspring of the women in the
widely-known Nurses Health Study II (NHS II) cohort, showed that when comparing children drinking one
glass or less per day with those drinking two glasses or more per day, girls drinking more were 1.3 cm taller and
boys drinking more were 2.3 cm taller130. A historical example is the doubling of the per capita cow's milk
consumption from 145 liters to 260 liters in the period between 1875 and 1900 in Switzerland, which
researchers identified as the probable cause for the increase of roughly 4 cm in the mean size of 19 year old army
recruits between 1875 and 1920. As almost everybody was drafted at this point in history, the sample was
representative for the male population of that time131. From these observations as well as the previously
discussed literature on growth, it could be expected that vegan children and adolescents should be smaller. The
aforementioned study on Swiss recruits also found that solving the problem of iodine deficiency through a
nation-wide public health intervention led to a second boost in height131. As use of iodine fortified foods and
supplements can vary between populations, it is important to account for this confounding influence.
Weight Mother's cow's milk consumption during pregnancy increased both infant size and weight in a
Danish study on 50'117 cases finding an association between increase in birth weight and quantified intakes of
protein from dairy products. Umbilical cord serum IGF-1 levels in LGA (large for gestational age) was elevated
when compared to their ADA (adequate for gestational age) and SGA (small for gestational ages) peers. Obese
children have been shown to have high serum IGF-1 levels, which is consistent with the repeated finding that
IGF-1 stimulates the transition from pre-adipocytes into adipocytes.
Insulin Cow's milk and most derived products except for cheese also have considerable insulinotropic effects,
despite them having only low glycemic indexes (GI). Hyperinsulinemia triggered solely by cow's milk was
demonstrated in a one-week intervention study of 24 eight year old boys. The addition of 200 ml of milk to a
low GI meal increased the insulin response by 300%, a reaction that could be expected from a very high GI meal
such as white bread. Higher postprandial insulin levels were observed as well in one week old infants fed cow's
milk formula versus mother's milk. This effect seems to be triggered by the whey protein fraction of milk.
Hyperinsulinemia, as it is characterized in adolescent obesity chronically suppresses IGFB-1, which in turn
further increases free IGF-1126.
Acne Elevated IGF-1 levels promote and increase in the facial sebum secretion in acne patients, and stimulates
sebocyte proliferation and differentiation as part of the development and progression of acne126. Later studies
found that through the mTORC1 pathway, SREBP1, the main transcription factor for lipogenesis, is activated,
which in turn converts the widely available amino acid leucine into fatty acids end steroids for sebaceus lipid
Premature menarche Interestingly, higher IGF-1 levels have been reported in pre-pubertal girls with
premature menarche126,133. Due to its large selection of variables in the KiGGS dataset, it is possible to verify this
association with by comparing the onset of menarche between the groups.
Cancers IGF-1 is a mitogenic hormone which means it generally stimulates growth, differentiation and
metabolism in human cells. Several studies showed an association between IGF-1 and breast, prostate, colorectal
and lung cancer, and the majority of human cancers have a high expression of IGF-1 receptors126. A 2004 meta-
analysis on 21 studies and 3'609 cases including 7'137 controls found that IGF-1 is moderately associated with
prostate cancer (odds ratio comparing 75th with 25th percentile 1.49, 95% CI: 1.14-1.95) and premenopausal (but
not post-menopausal) breast cancer (1.65, 95% CI: 1.26-2.08)134. A 2011 meta-analysis including data on 14'906
subjects showed a u-shaped association between IGF-1 levels and cancer mortality, with the lowest mortality
measured at medium IGF-1 levels. These researches expected higher IGF-1 levels to result in an increase of
more common cancers but had difficulty explaining the effect of decreased IGF-1 on cancer mortality,
suspecting possible confounders like bad nutritional state, muscle weakness and immobility, which themselves
are generally associated with decreased IGF-1 levels and could increase mortality135. Vegan adults have been
reported to have 8-9% less serum IGF-1 compared to vegetarians and omnivores128. This difference is interesting
when looking at a 1998 prospective study that demonstrated that when comparing men who subsequently
developed prostate cancer had 9% higher serum IGF-1 concentrations than men who remained healthy136. A
2016 systematic review and metaanalysis concluded that found a 15% lower incidence (RR 0.85; 95% CI, 0.75 to
0.95) of total cancers in vegans compared to the general population. Interestingly, the risk in the vegetarian
population was reduced only by half when compared to the vegan population (8%, RR 0.92, 95% CI 0.87 to
0.98)137. Because lifestyle factors and socioeconomic status are similar among vegetarians and vegans, and mostly
milk and eggs account for the nutritional difference between these groups, these results seem to suport the
hypothesis of mutagenic effects of cow's milk. However it cannot be excluded that e.g. differences in
socioeconomic status, lifestyle or plant food consumption could amount for this difference, or that eggs could be
the reason for this difference.
A closer look at the signaling pathway of cow's milk It is interesting to note that even when milk and dairy
products are ultra-heat processed or fermented, they retain the ability to raise human IGF-1 and insulin levels
more than any other source of dietary protein126. A 2013 study identified the mechanism by which cow's milk is
able to activate anabolic processes in humans. Milk of all mammals has the function to promote postnatal
growth and secure appropriate post-natal metabolic programming optimized by species. Metabolically, this
process of cell growth and proliferation, protein and lipid synthesis, anabolic metabolic processes and the
inhibition of autophagy are mediated by mechanistic target of rapamycin complex 1 (mTORC1). This complex
regulates protein synthesis in mammals and is activated through branched-chain amino acids, especially leucine,
through insulin, and through IGF-1. Leucine is the most common amino acid in whey (dairy) protein. As
discussed earlier, milk increases insulin levels IGF-1, but it was also discovered that through micro-RNA, milk is
able to simultaneously stimulate the mTORC1 complex directly. Micro-RNA is an archaic signaling and
communication system of eukaryotic cells, and many micro-RNAs of cow's and humans are identical. Compared
to all other fluids of the human body, milk has the highest amount of total RNAs. While raw milk contains the
highest amount of micro-RNAs, a substantial amount is still present after pasteurization138. The reason for this
is their resistance to low pH, RNase digestion, and high as well as low temperatures and their ubiquity in milk,
as they are not only present in free form, but also in exosomes, milk cells and milk fat globules139. It has been
confirmed both in vitro and in vivo that these micro-RNAs readily reach the systemic circulation of humans
subjects, and are subsequently absorbed by all kinds of different cells (mononuclear cells, macrophages, liver and
kidney cells), where they modify gene expression. It is estimated that from the 245 different micro-RNAs
available in cow's milk, the transcription of over 10'000 humans genes is modulated138. This epigenetic
modulation started around ten thousand years ago in the Neolithic revolution, and there is one documented
genetic adaptation humans have undergone to better process milk and dairy; the prolonged activity of lactase to
digest lactose well into the adult age. But most humans today do not even have this simple mutation. It is
questionable if the dairy adapted lactose tolerant people were able to adapt to an epigenetic stimulus of the
described magnitude, let alone the majority of humans who are not lactose tolerant. More so, due to modern
cooling facility and large scale pasteurization, milk usually is not fermented anymore, as it often was in the past.
Bacterial fermentation is destroying exosomes of milk and subsequently reduces micro-RNA content. Due to
this circumstance, industrial milk farming and recommendation of high intakes of cow's milk, today's humans
are exposed to dosages of these micro-RNAs that their bodies likely could not have adapted for.
Dioxins and PCB Dioxins (polychlorinated dibenzodioxins) and polychlorinated biphenyl (PCB) are fat-
soluble pollutants that accumulate in foods, and ultimately in the fatty tissue of humans. Their effects are best
documented in animal studies, especially disruption of thyroid functioning140 and when administered in high
doses, wasting syndrome (weight-loss, liver disease, metabolic disease)141. In humans these substances have
shown to cause chlorine acne, disrupt the immune system and have carcinogenic effects141,142. In children, PCB
has been shown to impair cognitive functioning, speed of information processing, verbal abilities, and visual
recognition memory, given previous prenatal exposure143. Swiss data A *B shows that dairy products
amount for 44% (54% if cheese is included) of total dioxin and PCB intake, which is similar to comparable
European countries141. Through this mechanism, the consumption of dairy products might further increase
aforementioned risk for neoplasia.
Summary on cow's milk Cow's milk has a variety of nutrients. It is an outstanding source of calcium, while
also containing the phosphorus, magnesium, potassium, zinc and selenium, as well as the vitamins A, D, E,
riboflavin, thiamin, niacin, piridoxin, folate and cobalamin. It is widely known that the lipid profile is not
optimal, being low on unsaturated fatty acids and rich in cholesterol. It is less known that, through different
pathways, cow's milk considerably raises IGF-1 levels and insulin response, ultimately stimulating the mTORC1
complex. Milk drinking adults typically show 8-10% and milk drinking children typically 20-30% higher IGF-1
levels. The mTORC1 complex is central in the regulation of mammalian protein synthesis. One of the most
relevant factors is leucine, another factor is micro-RNA, which is an evolutionary ancient way of post-natal
metabolic programming, with much micro-RNAs being identical between cows and humans. It is estimated that
micro-RNAs present in cow's milk modify the expression of 10'000 human genes. Apart from fermentation,
these micro-RNAs are resilient to degradation in the human digestive system, especially in their protective
vehicles, the exosomes. Industrial milk production and decreased use of fermentation due to modern cooling
technology has exposed humans to previously nonexistent amounts of said micro-RNA. It has been shown that
cow's milk consumption is associated with higher birth height and increased growth during childhood, with
children consuming two or more glasses being 1.3-2.3 cm taller than those drinking a glass or less, and young
adult Swiss men reaching a 4 cm larger average body height after per capita cow's milk consumption in the
population was doubled. Cow's milk consumption and IGF-1 have been shown to increase birth weight, and
obese children have high IGF-1 levels - one reason being its ability to stimulate differentiation of adipocytes.
The insulinotropic effects of cow's milk exceed greatly what could be expected from a response to its lactose
content, with the responsible ingredient being its whey protein fraction. Thereby, milk could be a significant
factor influencing early onsets of type 2 diabetes. There is also an association between IGF-1 and early
menarche, which can be tested using the KiGGS dataset. As IGF-1 is a mitogenic, there are associations with
Milk, cream, butter, yogurt (44%)
Plant foods (8%)
breast, prostate colorectal and lung cancers, with the majority of human cancers having a high amount of IGF-1
receptors. Pro-carcinogenic effects are further promoted through dioxins and PCB, for which cow's milk and
dairy products are the most significant source of in Western diets. When looking at this evidence, it seems
justified to question whether these pronounced metabolic and endocrinological effects of cow's milk outweigh
its nutritional benefits, or whether it would not be safer to get these beneficial nutrients from other sources
without the side effects of a life-long anabolic stimulus as well as extensive epigenetic modification, in addition
to the effects of the pollutants dioxins and PCB which have shown to have detrimental effects on neurological
developments in children and promote cancer. Regarding our dataset, we can expect vegan children to be
slightly smaller and lighter, but within a normal range, which will probably be a combination of a less energy
dense diet in combination with the absent anabolic stimulus of cow's milk. However, gross malnutrition and
iodine deficiency, as a confounding influence, has to be ruled out, and therefore other health parameters have to
be examined to test this hypothesis. Looking at the literature it is also likely that vegan girls have a later onset of
the menarche when compared to their vegetarian and omnivore peers.
2.5 Summary of the narrative literature review
To summarize the narrative literature review, a well-planned vegan nutrition is suitable for all stages of life,
including childhood and adolescence and provides advantages in the fields of overweight, diabetes,
cardiovascular disease and cancer. While the greatest risk seems to be cobalamin deficiency, other relevant
nutrients will be examined as well.
The assessment of a few nutrients which cannot be explored in this data set are only cited from one source.
Protein seems to be no matters of concern if caloric intake is adequate, and so is iodine, if iodized salt or sea
vegetables are incorporated into the diet. Because children have a higher risk for zinc deficiency, attention to
incorporating good vegan sources of zinc is recommended. With n-3 fatty acids it is important to aim for the
correct ratio and supplement DHA and EPA in pregnant, lactating or elderly vegans. Regarding infancy, the
Academy of Nutrition and Dietetics and the American Academy of Pediatrics have renewed their long-standing
statement that vegan diets can be appropriate for normal infant growth in 2016.
The assessment of the other nutrients was done more thoroughly, as knowledge will be expanded and discussed
as part of the M.D. dissertation, analyzing primary data from the KiGGS dataset. These are iron, calcium,
vitamin D, cobalamin, folate, potassium and magnesium. Other examined outcomes were weight and height,
with iterations on the influence of cow's milk.
Contrary to wide-spread belief, meat consumption does not seem to play a protective role from iron deficiency,
as no difference in prevalence has been found in studies of both adults and children, through different adaptive
mechanisms to low and plant iron, as well as the absorption of plant ferritin. Larger studies on adults suggest
that vegans have a better iron status than vegetarians, most likely due to absence of the inhibiting influence of
dairy and eggs on iron absorption. Iron intake of vegan children seems sufficient, yet these findings have to be
backed up by data on actual iron status of vegan children. Vitamin C can be a very effective agent for improving
iron status, so can be iron skillets or iron ingots, the latter of which are boiled for 10 minutes in any liquid or
broth based meals.
Despite good sources for calcium in both vegetables and fortified foods and drinks, vegans have on average
merely half the calcium intake of omnivores, which holds true for both adults and children. There is evidence
that achieving a positive calcium balance in children can be reached with low intakes, and low calcium intakes of
vegan children seems not to affect growth. However calcium intake has a clinically insignificant to small impact
on peak bone mass density at the end of the growth period. When protective lifestyle factors are factored out, it
was shown that a large proportion of vegans not meeting recommended calcium intakes (44.5% in the studied
sample) had a 30 percent higher risk for bone fractures. Therefore, vegans have to give proper calcium intakes
Vitamin D deficiency is generally considered a widespread problem among all age groups. Dietary intakes of
vitamin D are considerably lower among vegans, although no detrimental effect of these decreased levels on
BMD could be shown. Lacking sunlight seems to play the dominant primary role regarding vitamin D status,
usually providing 90% of the demand. Nonetheless, aside from more sun-exposure, deficiency can be addressed
with higher dietary vitamin D intake using supplements. No data on vitamin D plasma levels of vegan children
is available as of yet.
Low cobalamin levels and cobalamin deficiency has a high prevalence in vegan populations, even though it
cannot be excluded that few individuals have sufficient endogenous synthesis. The main reason for this wide-
spread problem is the low rate of supplementation, estimated at around 40%. There is tentative evidence that the
awareness for supplementation higher among vegan parents in regard of their children, with in one instance
much as at least 78% of all children receiving supplements. However, this number is from a collective
community in the 1970ies and 1980ies, and might not be representative for today's general vegan population.
From this population, we also have the only data on cobalamin status in vegan children. Therefore there is an
urgent need for further investigation on both the prevalence of cobalamin deficiency and motivations leading
parents to avoid supplementation of their children. Furthermore, monitoring blood levels of cobalamin is
indicated regarding vegan children, and in case no such monitoring is being undertaken, being watchful of
neurological or neuro-psychiatric symptoms.
Regarding vitamin deficiency, it can be estimated that among omnivores around 35% of all children have
insufficient plasma folate levels and 15% are deficient, a problem which is more pronounced in adulthood,
where up to 58% are deficient. The relative risk of vegan adults developing folate deficiency can be estimated to
be smaller by a factor of four. While data on plasma levels of vegan children is only tentative, it could be
expected that folate deficiency is rare within this group. Vegan diet has a higher content of both potassium and
magnesium. No evidence on potassium or magnesium status could be found regarding vegan children or
adolescents, but there is no reason to assume that potassium status is decreased. Meat, fish, eggs and especially
dairy predict high BMI and vegan children are lighter than their omnivore peers. Researchers have suggested
that vegetarian diets could be an effective tool to combat increasing prevalence child overweight and obesity and
its ramifications. Because animal proteins, especially dairy products might play a key role in these differences,
the role of milk and dairy was examined more closely, revealing its ability to considerably raise plasma IGF-1
and insulin levels, and epigenetically modifying estimated 10'000 genes through micro-RNA. Through its
hormonal influence, milk has been shown to further increase growth in already well-fed populations. Through
the promotion of overweight and the stimulation of insulin response, milk is likely to play a significant role in
the development of type 2 diabetes, which affects a growing number of children and adolescents. Furthermore,
increased IGF-1 is not only suspected to play a role in early menarche or acne, but as a mitogen has been
associated with neoplasia, especially prostate cancer and pre-menopausal breast cancer, with the majority of
human cancers having a high expression of IGF-1 receptors. The examined group of vegan children is expected
to be slightly smaller and lighter, but within a normal range, which will probably be a combination of a less
energy dense diet in combination with the absent anabolic stimulus of cow's milk. It is also likely that vegan girls
have a later onset of the menarche when compared to their vegetarian and omnivore peers. A tabularized
overview of these finding is seen in 1.
Outcome variable Verdict on vegan adults
Protein Adequacy for all ages and for athletes.
n-3 Fatty Acids Adecuacy. DHA/EPA supplementation for pregnant and elderly.
Iodine Adequacy, if iodine sources (salt, seavegetables) ar utilized.
Calcium Increased fractures in old age for half of the populatin not meeting recommended intakes
Vitamin D Sunlight as deciding factor. Supplementation can be recommended.
Cobalamin (Vitamin B12) Extended risk of deficiency if not supplemented.
Folate Deficiency very common among omnivores, 4x less likely in vegans.
Potassium Vegans have higher intakes.
Magnesium Vegans have higher intakes.
Weight and Height Lighter and slightly less tall, but within a healthy range
Outcome variable Verdi ct on vegan ch ildren and adolescents
Protein Adequate, if caloric intakes are adequate.
n-3 Fatty Acids Adequacy. Use 3:1 ratio.
Zinc Adequacy, highe r zinc intakes recommended.
Iodine Adequacy, if iodine sources (salt, seavegetables) ar used.
Iron No evidence on plasma status in vegan children.
Calcium Half of recommended intakes, but no effect on height.
Vitamin D No data on vegan children.
Cobalamin (Vitamin B12) No data on vegan children. Risk if not supplem ented.
Folate Probably analogous to adults.
Potassium No data on vegan children.
Magnesium No data on vegan children.
Weight and Height Lighter and slightly less tall, but within a healthy range.
Table 1 – ! .
3.1 Study populations
A well-planned vegan diet was deemed suitable for all stages of life, including childhood and adolescence by the
Academy of Nutrition and Dietetics, the world's largest organization of food and nutrition professionals, as well
as the American Academy of Pediatrics. Vegan diet provides advantages in the fields of overweight, diabetes,
cardiovascular disease and cancer. Apart from direct effects on health, the environmental sustainability of vegan
diets must be considered as well. Vegan diets use fewer resources and are inflicting much less environmental
damage than diets rich in animal products. There are also certain advantages that a reduction of animal farming
would entail in regard to both human and non-human health. But those will be discussed later on.
From their recommendations, it is largely clear what nutrients have to be taken care of to secure normal
development. However the next question is how often these conditions apply to the general vegan population,
and how they differ within its sub-populations. For example, sub-populations that use deductions of the
argument as a dietary guide, what I called such as raw vegans or rastafarian vegans, are
often characterized by an inherent distrust towards evidence-based medicine. They are more prone to
experience chemophobia, leading to insufficient or no supplementation of important nutrients. From this
observation, I tried to identify variables which would be an expression of this in the KiGGS
dataset. Those variables were assessing usage of alternative and complementary medicine, vaccination status and
avoidance of tooth-paste containing fluoride. It is speculated that if those variable will predict supplementation,
they could be used to identify vegans who are at risk, enabling better targeting in the context of health
prevention. The results and their discussion will be available in the M.D. dissertation.
For future research, it is my recommendation that raw vegans and rastafarian vegans should be differentiated
from those who were defined as standard vegans, as the latter are basing their diet plans on evidence-based
advice and typically have no issues with supplementation. Pooling these rather diverse groups together is likely
to produce results that do justice to none of them. Literature referring only to proxy populations of vegans such
as black hebrews, anthrophosophes, macrobiotics or general rastafarians should be ignored when trying to come
to conclusions about people on standard vegan diets, yet they still exhibit some influence on modern guidelines,
despite there being better evidence.
3.2 Narrative literature review
When it comes to nutrients, it can be reasonably assumed that standard vegans informed by scientific evidence
are able to perform adequate supplementation and follow dietary guidelines, but this is not necessarily the case
for natural vegans. For example, vegan children need adequate amounts of caloric intake, which, as evidence
suggests, will also ensure sufficient protein intakes. This could be a risk if children are fed a raw diet, as this diet
is known to lead to considerable weight loss in most adults. Another issue is supplementation, which is often
rejected by natural vegans. Cobalamin is the most important form of supplementation for pregnant or lactating
women as well as their children. Natural vegans could use Spirulina or Chlorella algae, but this is an expensive
and less secure source of cobalamin, and sometimes this population uses only alleged sources, some of which
have been confirmed not to contain cobalamin. Raw diet populations in general have been shown to have very
low rates of cobalamin supplementation. Having said that, cobalamin supplementation rates of mixed vegan
groups have been shown to be low in general, reaching only 40% in adults. However, one study suggested that
supplementation is taken more seriously in vegan parents, as 78% supplemented cobalamin to their children,
and there is some evidence that supplementation rates might be higher in the big part of the vegan population
that adopted this diet within the last six years. If no sea vegetables are consumed, iodine should be
supplemented. Pregnant women should supplement both DHA and EPA. Because those supplements are micro-
algae based, they might be more acceptable to natural vegans.