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Vitamin
B12 and vegan diets
Lessons from
history
B12 is an exceptional
vitamin. It is required in smaller amounts than any other known
vitamin. Ten micrograms of B12 spread over a day appears to supply
as much as the body can use. In the absence of any apparent dietary
supply, deficiency symptoms usually take five years or more to develop
in adults, though some people experience problems within a year.
A very small number of individuals with no obvious reliable source
appear to avoid clinical deficiency symptoms for twenty years or
more. B12 is the only vitamin that is not recognised as being reliably
supplied from a varied wholefood, plant-based diet with plenty of
fruit and vegetables, together with exposure to sun. Many herbivorous
mammals, including cattle and sheep, absorb B12 produced by bacteria
in their own digestive system. B12 is found to some extent in soil
and plants. These observations have led some vegans to suggest that
B12 was an issue requiring no special attention, or even an elaborate
hoax. Others have proposed specific foods, including spirulina,
nori, tempeh, and barley grass, as suitable non-animal sources of
B12. Such claims have not stood the test of time.
In over 60 years
of vegan experimentation only B12 fortified foods and B12 supplements
have proven themselves as reliable sources of B12, capable of supporting
optimal health. It is very important that all vegans ensure they
have an adequate intake of B12, from fortified foods or supplements.
This will benefit our health and help to attract others to veganism
through our example.
Getting an
adequate amount of B12
National recommendations
for B12 intakes vary significantly from country to country. The
US recommended intake is 2.4 mcgs a day for ordinary adults rising
to 2.8 mcgs for nursing mothers. The German recommendation is 3
mcgs a day. Recommended intakes are usually based on 50% absorption,
as this is typical for small amounts from foods. To meet the US
and German recommendations you need to obtain sufficient B12 to
absorb 1.5 mcgs per day on average. This amount should be sufficient
to avoid even the initial signs of inadequate B12 intake, such as
slightly elevated homocysteine and MMA levels, in most people. Even
slightly elevated homocysteine is associated with increased risk
of many health problems including heart disease in adults, preeclampsia
during pregnancy and neural tube defects in babies.
Achieving an
adequate B12 intake is easy and there are several methods to suit
individual preferences. Absorption of B12 varies from about 50%,
if about 1 mcg or less is consumed, to about 0.5% for doses of 1000
mcgs (1 mg) or above. So the less frequently you consume B12, the
higher the total amount needs to be to give the desired absorbed
amount.
Frequent use
of foods fortified with B12 so that about one microgram of B12 is
consumed three times a day with a few hours in between will provide
an adequate amount. Availability of fortified foods varies from
country to country and amounts of B12 vary from brand to brand,
so ensuring an adequate B12 supply from fortified foods requires
some label reading and thought to work out an adequate pattern to
suit individual tastes and local products.
Taking a B12
supplement containing ten mcgs or more daily provides a similar
absorbed amount to consuming one mcg on three occasions through
the day. This may be the most economical method as a single high
potency tablet can be consumed bit by bit. 2000 mcgs of B12 consumed
once a week would also provide an adequate intake. Any B12 supplement
tablet should be chewed or allowed to dissolve in the mouth to enhance
absorption. Tablets should be kept in an opaque container. As with
any supplement it is prudent not to take more than is required for
maximum benefit, so intakes above 5000 mcg per week should be avoided
despite lack of evidence for toxicity from higher amounts.
All three options
above should meet the needs of the vast majority of people with
normal B12 metabolism. Individuals with impaired B12 absorption
may find that the third method, 2000mcg once a week, works best
as it does not rely on normal intrinsic factor in the gut. There
are other, very rare, metabolic defects that require completely
different approaches to meeting B12 requirements. If you have any
reason to suspect a serious health problem seek medical advice promptly.
Symptoms of
B12 deficiency
Clinical deficiency
can cause anaemia or nervous system damage. Most vegans consume
enough B12 to avoid clinical deficiency. Two subgroups of vegans
are at particular risk of B12 deficiency: long-term vegans who avoid
common fortified foods (such as raw food vegans or macrobiotic vegans)
and breastfed infants of vegan mothers whose own intake of B12 is
low.
In adults typical
deficiency symptoms include loss of energy, tingling, numbness,
reduced sensitivity to pain or pressure, blurred vision, abnormal
gait, sore tongue, poor memory, confusion, hallucinations and personality
changes. Often these symptoms develop gradually over several months
to a year before being recognised as being due to B12 deficiency
and they are usually reversible on administration of B12. There
is however no entirely consistent and reliable set of symptoms and
there are cases of permanent damage in adults from B12 deficiency.
If you suspect a problem then get a skilled diagnosis from a medical
practitioner as each of these symptoms can also be caused by problems
other than B12 deficiency.
Infants typically
show more rapid onset of symptoms than adults. B12 deficiency may
lead to loss of energy and appetite and failure to thrive. If not
promptly corrected this can progress to coma or death. Again there
is no entirely consistent pattern of symptoms. Infants are more
vulnerable to permanent damage than adults. Some make a full recovery,
but others show retarded development.
The risk to
these groups alone is reason enough to call on all vegans to give
a consistent message as to the importance of B12 and to set a positive
example. Every case of B12 deficiency in a vegan infant or an ill
informed adult is a tragedy and brings veganism into disrepute.
The
homocysteine connection
This is not
however the end of the story. Most vegans show adequate B12 levels
to make clinical deficiency unlikely but nonetheless show restricted
activity of B12 related enzymes, leading to elevated homocysteine
levels. Strong evidence has been gathered over the past decade that
even slightly elevated homocysteine levels increase risk of heart
disease and stroke and pregnancy complications. Homocysteine levels
are also affected by other nutrients, most notably folate. General
recommendations for increased intakes of folate are aimed at reducing
levels of homocysteine and avoiding these risks. Vegan intakes of
folate are generally good, particularly if plenty of green vegetables
are eaten. However, repeated observations of elevated homocysteine
in vegans, and to a lesser extent in other vegetarians, show conclusively
that B12 intake needs to be adequate as well to avoid unnecessary
risk.
Testing
B12 status
A blood B12
level measurement is a very unreliable test for vegans, particularly
for vegans using any form of algae. Algae and some other plant
foods contain B12-analogues (false B12) that can imitate true B12
in blood tests while actually interfering with B12 metabolism. Blood
counts are also unreliable as high folate intakes suppress the anaemia
symptoms of B12 deficiency that can be detected by blood counts.
Blood homocysteine testing is more reliable, with levels less than
10 mmol/litre being desirable. The most specific test for B12 status
is methylmalonic acid (MMA) testing. If this is in the normal range
in blood (<370 nmol/L) or urine (less than 4 mg /mg creatinine)
then your body has enough B12. Many doctors still rely on blood
B12 levels and blood counts. These are not adequate, especially
in vegans.
Is there
a vegan alternative to B12-fortified foods and supplements?
If for any reason
you choose not to use fortified foods or supplements you should
recognise that you are carrying out a dangerous experiment - one
that many have tried before with consistently low levels of success.
If you are an adult who is neither breast-feeding an infant, pregnant
nor seeking to become pregnant, and wish to test a potential B12
source that has not already been shown to be inadequate, then this
can be a reasonable course of action with appropriate precautions.
For your own protection, you should arrange to have your B12 status
checked annually. If homocysteine or MMA is even modestly elevated
then you are endangering your health if you persist.
If you are breast
feeding an infant, pregnant or seeking to become pregnant or are
an adult contemplating carrying out such an experiment on a child,
then don’t take the risk. It is simply unjustifiable.
Claimed sources
of B12 that have been shown through direct studies of vegans to
be inadequate include human gut bacteria, spirulina, dried nori,
barley grass and most other seaweeds. Several studies of raw food
vegans have shown that raw food offers no special protection.
Reports that
B12 has been measured in a food are not enough to qualify that food
as a reliable B12 source. It is difficult to distinguish true B12
from analogues that can disrupt B12 metabolism. Even if true B12
is present in a food, it may be rendered ineffective if analogues
are present in comparable amounts to the true B12. There is only
one reliable test for a B12 source – does it consistently prevent
and correct deficiency? Anyone proposing a particular food as a
B12 source should be challenged to present such evidence.
A
natural, healthy and compassionate diet
To be truly
healthful, a diet must be best not just for individuals in isolation
but must allow all six billion people to thrive and achieve a sustainable
coexistence with the many other species that form the “living
earth”. From this standpoint the natural adaptation for most
(possibly all) humans in the modern world is a vegan diet. There
is nothing natural about the abomination of modern factory farming
and its attempt to reduce living, feeling beings to machines. In
choosing to use fortified foods or B12 supplements, vegans are taking
their B12 from the same source as every other animal on the planet
– micro-organisms – without causing suffering to any sentient
being or causing environmental damage.
Vegans using
adequate amounts of fortified foods or B12 supplements are much
less likely to suffer from B12 deficiency than the typical meat
eater. The Institute of Medicine, in setting the US recommended
intakes for B12 makes this very clear. “Because 10 to 30 percent
of older people may be unable to absorb naturally occurring vitamin
B12, it is advisable for those older than 50 years to meet their
RDA mainly by consuming foods fortified with vitamin B12 or a vitamin
B12-containing supplement.” Vegans should take this advice
about 50 years younger, to the benefit of both themselves and the
animals. B12 need never be a problem for well-informed vegans.
Good information
supports vegan health, pass it around.
Further information:
Dietary Reference
Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin
B12, Pantothenic Acid, Biotin, and Choline, National Academy Press,
1998 ISBN 0-309-06554-2 (http://books.nap.edu/books/0309065542/html/306.html#pagetop)
Homocysteine
in health and disease, ed. Ralph Carmel and Donald W. Jacobsen,
Cambridge University Press, 2001, ISBN 0-521-65319-3
Credits:
This information
sheet was prepared by Stephen Walsh (Stephen_walsh@vegans.fsnet.co.uk),
a UK Vegan Society trustee, and other members of the International
Vegetarian Union science group (IVU-SCI), in October 2001.
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