Defending eating habits seems to be a primal instinct for people.
These days Westerners are running out of excuses for their gluttony.
Well-read people no longer believe
meat is necessary to meet our protein needs or
that milk is the favored source of
calcium. With the crumbling of these two time-honored
battle fronts the vitamin B12 issue has become the trendy topic whenever
a strict vegetarian (vegan) diet is discussed. Since the usual dietary
source of vitamin B12 for omnivores is the flesh of other animals, the
obvious conclusion is that those who choose to avoid eating meat are
destined to become B12 deficient. There is a grain of truth in this
concern, but in reality an otherwise healthy strict vegetarian’s risk of
developing a disease from B12 deficiency by following a sensible diet is
extremely rare—less than one chance in a million.
I knew forty years ago that vitamin B12 would become the last bastion
for meat- and dairy-lovers (and the industries that profit from them),
because this is the only criticism with any merit that could be lodged
against the McDougall Diet. In order to avoid that condemnation and the
small risk of harming anyone, I have recommended and printed in the
beginning of my books and DVDs the following advice:
follow the McDougall Diet for more than 3 years, or if you are
pregnant or nursing, then take a minimum of 5 micrograms of
supplemental vitamin B12 each day.
Avoid B12 Deficiency; Get Heart Disease and Cancer
Vitamin B12 is involved in the metabolism of all cells in the body;
but the effects of deficiencies are first seen in the blood and then the
nervous system. An anemia, called megaloblastic anemia, because it is
characterized by large red blood cells, is a common manifestation of
deficiency. The low red blood cell count is very well tolerated by the
patient even when severe, and is always cured by the taking of small
amounts of B12. Mild problems with the nervous system characterized by
numbness and tingling in the hands and feet also develop. These
sensations are reversible in early stages; however, damage to the
nervous system can become much more severe and irreversible after
Take a moment to compare the possible consequences of your dietary
decisions. You could choose to eat lots of B12-rich animal foods and
avoid the one-in-a-million chance of developing a reversible anemia
and/or even less common, damage to your nervous system. However, this
decision puts you at a one-in-two chance of dying prematurely from a
heart attack or stroke; a one-in-seven chance of breast cancer or a
one-in-six chance of prostate cancer. The same thinking results in
obesity, diabetes, osteoporosis, constipation, indigestion, and
arthritis. All these conditions caused by a B12-sufficient diet are
found in the people you live and work with daily. How many vegans have
you met with B12 deficiency anemia or nervous system damage? I bet not
one! Furthermore, you have never even heard of such a problem unless you
have read the attention-seeking headlines of newspapers or medical
Sensationalism Surrounds B12-Deficient Vegetarians
Rare cases of B-12 deficiency suspected to be caused by following a
vegetarian diet make media-selling banners, because “people love to hear
good news about their bad habits.” However, in depth research reveals
that many of these “vegetarians” also suffer from generalized
malnutrition—not just isolated B12 deficiency from a diet based on plant
foods. For example, the March 23, 2000 issue of the New England
Journal of Medicine published a letter (not a scientific article)
with the provocative title, “Blindness in a Strict Vegan.”
letter described a 33-year old man who was found to have severe loss of
vision (bilateral optic neuropathy). He had started a strict vegetarian
diet at age 20. Tests showed he suffered from deficiencies of vitamins
A, C, D, E, B1, B12 and folic acid, as well as zinc and selenium. All
combined, these deficiencies clearly indicate severe malnutrition. B12
injections corrected his anemia, but not his visual loss.
Do you see the disconnection between the case history and the
headlines? Starches, vegetables, and fruits are very rich sources of
folic acid and vitamin C (as well as A, E, B1, zinc and selenium). His
malnourished condition most likely was caused by an intestinal disease
and/or an unhealthy “vegetarian” diet.2 The headlines published
worldwide that followed this letter reassured meat- and dairy-lovers
that becoming a vegetarian was an unwise decision. Examination of many
reported cases of B12 deficiency connected to a vegetarian diet in both
children and adults reveals similar confounding factors.1-6 The patients
may have subtle malabsorption and often come from conditions of poverty
and/or live an eccentric lifestyle—their health problems are not simply
due to avoiding animal foods. However, I do believe there are very rare
patients with diseases due to lack of B12 from following a strict
vegetarian diet for years—while others have disagreed with me and
believe that all cases have confounding factors.7
Germs for Good Health
Although vitamin B12 is found in animal foods it is not synthesized
by plants or animals. Only bacteria make biologically active vitamin
B12—animal tissues store “bacteria-synthesized B12,” which can then be
passed along the food chain by animals eating another animal’s tissues.
Ruminants (like cows, goats, sheep, giraffes, llamas, buffalo, and deer)
are unique in that bacteria in their rumens (stomachs) synthesize
vitamin B12, which is then passed down and absorbed by their small
intestines. Lions and tigers get their B12 from eating these grazers.
The human gut also contains B12-synthesizing bacteria, living from
the mouth to the anus.8 The presence of these bacteria is an important
reason that disease from vitamin B12 deficiency occurs very rarely in
people, even those who have been strict vegetarians (vegans) all of
their lives. The colon contains the greatest number of bacteria (4
trillion/cc of feces), and here most of our intestinal B12 is produced.
However, because B12 is absorbed in the ileum, which lies upstream of
the colon, this plentiful source of B12 is not immediately available for
absorption—unless people eat feces (don’t gasp). Feces of cows,
chickens, sheep and people contain large amounts of active B12. Until
recently most people lived in close contact with their farm animals, and
all people consumed B12 left as residues by bacteria living on their
un-sanitized vegetable foods.
Why would a plant-food-based diet, heralded as a preventative and
cure for our most common chronic diseases be deficient in any way? Such
a diet appears to be the proper, intended, diet for humans, except for
this one blemish. The reason for this apparent inconsistency is we now
live in unnatural conditions—our surroundings have been sanitized by
fanatical washing, powerful cleansers, antiseptics, and antibiotics.
Since the germ theory of disease was developed by Louis Pasteur in 1877
our society has waged an all-out war on these tiny creatures—most of
them extremely beneficial with only a very few acting as pathogens. The
rare case of B12 deficiency may be one important consequence of too much
Efficiency Is the Other Reason Deficiency Is Rare
The human body has evolved with highly efficient and unique
mechanisms to absorb, utilize, and conserve this vitamin. Our daily
requirement is less than 3 micrograms a day—one microgram is
one-millionth of a gram (1/1,000,000 gram).9 Which means, by design,
people are expected to be exposed to only miniscule amounts of this
Vitamin B12 is the only nutrient that requires a cofactor for
efficient absorption. The cells of the stomach produce a substance,
called intrinsic factor, which combines—after the acidic digestion of
the food in the stomach—with the B12 released from food. This “intrinsic
factor-B12 complex” then travels to the end of the small intestine (the
ileum) where it is actively absorbed.
There is a second, much less efficient process, called “the passive
absorption of B12” which also occurs in the intestine. This mechanism
does not use intrinsic factor and as a result it is 1/1000 as efficient.
But by consuming very large doses of oral B12, passive absorption will
correct B12 deficiency even for patients with diseases of the stomach
and small intestine.
On average, for someone raised on the Western diet, about 2 to 5
milligrams of B12 are stored, mostly in the liver. This means most
people have at least a three year reserve of this vital nutrient.
Conservation of B12 by the body boosts the time this supply lasts by
10-fold. After excretion through the bile into the intestines most of
the B12 is reabsorbed by the ileum for future use. As a result of this
recirculation it actually takes, on average, 20 to 30 years to become
deficient after becoming a strict vegan. That is if no vitamin B12 were
consumed—which is impossible, even on a strict vegan diet, because of
bacterial sources of B12 from the person’s bowel, contaminated vegetable
foods, and the environment.
There is evidence that suggests that during pregnancy and nursing a
mother is more dependent on B12 from her diet, because B12 stored in the
woman’s body is less available for the baby.10 Therefore, during these
important times, B12 supplementation should be used by a vegan mother.
Biochemical Changes Occur with Low B12
Blood levels of B12 can be measured directly in the blood and are a
means to help diagnose deficiency. Values above 150 pg/ml (picograms per
milliliter) are considered normal, and levels below 80 pg/ml represent
unequivocal B12 deficiency.11
Within the body, biochemical reactions require B12. A deficiency can
cause an interruption of normal metabolism and result in the
accumulation of substances like methylmalonic acid and the amino acid,
homocysteine. Tests showing increases in these metabolic products are
used to diagnose “early B12 deficiency”—before any actual disease
Elevated homocysteine has been associated with an increased risk of
common Western diseases (heart attacks, strokes, etc.). However, this
amino acid itself does not cause disease—it serves as a marker for
identifying people who consume large amounts of animal foods. Eating
meat, poultry, fish, and cheese raises levels of homocysteine—as well as
these same foods making people fat and sick. Efforts to lower
homocysteine with supplements of folic acid and/or B12 have produced no
reduction in heart disease or stroke12—and in fact the use of folic acid
supplements increases the risk of cancer, heart disease, and overall
The long-term consequences of B-12 supplementation are unknown; so
far this vitamin appears to be non-toxic and beneficial. As a result, I
currently have no hesitation recommending supplements to strict
vegetarians in order to prevent the rare chance of a deficiency
Intestinal Diseases, Not Dietary Deficiency, Cause Most B12 Problems
Almost all cases of vitamin B12 deficiency seen in patients today and
in the past are due to diseases of the intestine, and are not due to a
lack of B12 in their diet. Damage to the stomach (parietal cells)
usually from an autoimmune disease or surgery halts the production of
intrinsic factor. Damage to the ileum, preventing reabsorption and
interrupting recirculation, causes the loss of B12. Over a period of 3
to 6 years the body’s stores of vitamin B12 are depleted. The disease
that results is called pernicious anemia. (The word pernicious refers to
a tendency to cause death or serious injury.) Prior to the development
of a treatment with liver extracts in 1926 this condition was
History of B12 Deficiency from Pernicious Anemia (PA)14-15
1824—A fatal form of anemia associated with stomach degeneration
was first described by J.S. Combe of Edinburgh.
1860—Austin Flint recognized the nutritional basis of this
anemia and the degeneration of the stomach in this disease.
1872—Biermer, in Switzerland, coined the concept of
pernicious anemia (PA) based on the inevitably fatal outcome of
1880’s—Ehrlich added that patients with this anemia had giant
peripheral blood cells, so called megaloblasts.
1887—Lichtheim describes an association of PA and spinal cord
1921—Levine and Ladd reported that no stomach acid was found
in patients with PA.
1925—William Castle fed cooked ground beef to healthy young
men and one hour later, removed the gastric juice which
contained partly digested beef, and placed it in the stomach of
patients with pernicious anemia. As a control, he gave ground
beef without gastric juice to another group of patients. The
experimental group responded with the production of new blood
cells, but the control group did not. He postulated that some
unknown, but essential, interaction between beef muscle as an
extrinsic factor and normal human gastric juice as an intrinsic
factor was required.
1926—Two American physicians, Minot and Murphy, described a
raw liver diet (liver therapy) that cured PA in the Journal
of the American Medical Association. They received the Nobel
Prize in Physiology and Medicine in 1934 for their work.
1941—Folic acid received its name following its isolation
from spinach (from the Latin ‘folium’ meaning leaf). Folic acid
deficiency causes megaloblastic anemia, but not nervous system
1945—Folic acid was synthesized and found to be effective in
treating all types of megaloblastic anemia, but especially those
that proved refractory to liver preparations such as the
megaloblastic anemia of sprue, celiac disease, pregnancy and
1948—Two independent teams in the United States and England
isolated the mysterious extrinsic factor, vitamin B12, in
1955—Dorothy Crowfoot Hodgkin, a British chemist, elucidated
the unique and complex chemical structure of this large
molecule, in its cyanocobalamin form, using X-Ray
crystallography. She was awarded the Nobel Prize for Chemistry
Sources of Vitamin B12
As little as 0.3 to 0.65 micrograms per day of vitamin B12 has cured
people of megaloblastic anemia;9 however, to add an extra margin of
safety I have recommended a higher dosage of 5 micrograms per day. You
may be surprised to discover that you cannot purchase these tiny
dosages. Supplements sold contain 500 to 5000 micrograms per pill. These
exaggerated concentrations will correct by passive absorption B12
deficiency caused by disease of the intestine.16-17 Everyone else is
being overdosed by a factor of 1000. If you are an otherwise healthy
vegan and are using typical dosages of B12 (500 micrograms or more per
pill), a weekly dose of this vitamin will be more than sufficient.
You will often find B12 sold under its proper name. Because vitamin
B12 contains one molecule of the mineral cobalt, the scientific name is
Cobalamin. As a food additive and a supplement pill, vitamin B12 is
usually found in the form cyanocobalamin. The effectiveness of this
“cyanide complex” for treating neurologic problems has been questioned;
therefore, other forms, such as methylcobalamin and hydroxycobalamin may
be better choices for the prevention and treatment of B12-related
Choosing a bioactive form of B12 is important. There are many
B12-like substances called analogues found in food supplements, such as
spirulina and other algae—these are ineffective and should not be relied
upon.19 Foods fermented by bacteria, such as tempeh, and miso; as well
as sea vegetables (nori), have been recommended as sources of B12. Miso
and tempeh do not contain B12.20 Nori—the dried green and purple lavers
commonly used to make sushi—has been tested and found to have
substantial amounts of active vitamin B12 and has been recommended a
“most excellent source of vitamin B12 among edible seaweeds, especially
for strict vegetarians.”20,21 (Nori obtains its B12 from symbiotic
bacteria that live on it.22) However, there is still some uncertainty
about nori as a reliable B12 source; therefore, I suggest if you do
choose this seaweed that you should monitor your B12 levels by blood
tests now, and if adequate, every 3 years.
In order to minimize your risk of any health problems, I recommend
you and your family follow a diet based on starches, vegetables, and
fruits. To avoid the extremely rare chance of becoming a national
headline, add a reliable B12 supplement. By making this addition to a
healthy diet you can’t go wrong, nor will you suffer from any
justifiable criticism of your McDougall Diet delivered by well-meaning
family and friends
References:1) Milea D, Cassoux N, LeHoang P. Blindness
in a strict vegan. N Engl J Med. 2000 Mar 23;342(12):897-8.
2) Lavine JB. Blindness in a vegan. N Engl J Med. 2000 Aug
3) Carmel R. Nutritional vitamin-B12 deficiency. Possible
contributory role of subtle vitamin-B12 malabsorption. Ann Intern Med.
4) No authors. Vegetarian diet and vitamin B12 deficiency. Nutr
Rev. 1978 Aug;36(8):243-4.
5) Avci Z, Turul T, Aysun S, Unal I. Involuntary movements and
magnetic resonance imaging findings in infantile cobalamine (vitamin
B12) deficiency. Pediatrics. 2003 Sep;112(3 Pt 1):684-6.
6) February 2003 McDougall Newsletter: Vegan Diet Damages Baby’s
Brain – Sensationalism! http://www.nealhendrickson.com/mcdougall/030200puVeganDietDamages.htm
7) Immerman AM. Vitamin B12 status on a vegetarian diet. A clinical
review. World Rev Nutr Diet. 1981;37:38-54.
8) Albert MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human
small intestinal bacteria. Nature. 1980 Feb 21;283(5749):781-2.
9) Stabler SP, Allen RH. Vitamin B12 deficiency as a worldwide
problem. Annu Rev Nutr. 2004;24:299-326.
10) Koebnick C, Hoffmann I, Dagnelie PC, Heins UA, Wickramasinghe SN,
Ratnayaka ID, Gruendel S, Lindemans J, Long-term ovo-lacto vegetarian
diet impairs vitamin B-12 status in pregnant women. J Nutr. 2004
11) Ting RZ, Szeto CC, Chan MH, Ma KK, Chow KM. Risk factors of
vitamin B(12) deficiency in patients receiving metformin. Arch Intern
Med. 2006 Oct 9;166(18):1975-9.
12 Wierzbicki AS. Homocysteine and cardiovascular disease: a review
of the evidence. Diab Vasc Dis Res. 2007 Jun;4(2):143-50.
13. McDougall Newsletter. Folic Acid Supplements are a Health Hazard
October 2005 http://www.drmcdougall.com/misc/2005nl/oct/051000folic.htm
14) Chanarin I. Historical review: a history of pernicious anaemia.
Br J Haematol. 2000 Nov;111(2):407-15.
15) Okuda K. Discovery of vitamin B12 in the liver and its absorption
factor in the stomach: a historical review. J Gastroenterol Hepatol.
16) Butler CC, Vidal-Alaball J, Cannings-John R, McCaddon A, Hood K,
Papaioannou A, Mcdowell I, Goringe A.Oral vitamin B12 versus
intramuscular vitamin B12 for vitamin B12 deficiency: a systematic
review of randomized controlled trials. Fam Pract. 2006
17) Vidal-Alaball J, Butler CC, Cannings-John R, Goringe A, Hood K,
McCaddon A, McDowell I, Papaioannou A. Oral vitamin B12 versus
intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane
Database Syst Rev. 2005 Jul 20;(3):CD004655.
18) Freeman AG. Hydroxocobalamin versus cyanocobalamin. J R Soc
Med. 1996 Nov;89(11):659.
19) Watanabe F, Takenaka S, Kittaka-Katsura H, Ebara S, Miyamoto E.
Characterization and bioavailability of vitamin B12-compounds from
edible algae. J Nutr Sci Vitaminol (Tokyo). 2002 Oct;48(5):325-31.
20) Watanabe F. Vitamin B12 sources and bioavailability. Exp Biol
Med (Maywood). 2007 Nov;232(10):1266-74.
21) Watanabe F, Takenaka S, Katsura H, Masumder SA, Abe K, Tamura Y,
Nakano Y. Dried green and purple lavers (Nori) contain substantial
amounts of biologically active vitamin B(12) but less of dietary iodine
relative to other edible seaweeds. J Agric Food Chem. 1999
22) Croft MT, Lawrence AD, Raux-Deery E, Warren MJ, Smith AG. Algae
acquire vitamin B12 through a symbiotic relationship with bacteria.
Nature. 2005 Nov 3;438(7064):90-3.