Liza May wrote:
> << The New England Journal of Medicine (12/7/78, Page 1319) notes that
> Vitamin B-12 is manufactured by microorganisms, making it possible to
> obtain vitamin B-12 from certain seeds and nuts, and from soybean
> products.
For an up to date update;
First a personal note. Recently, In the last few years of my own
personal and professional practice I have seen many longterm vegans who
followed either all raw food diets or mostly raw food hygienic diets who
had extremely low serum B12 levels in the neighborhood of 65-90 (norm is
considered arounbd 200 and recent studies have indicated 250 may be
healthier). These were peoply who strictly followed thier diets in
addition to an extremely healthy lifestyle. Some had also already begun
to manifest clinical symptoms of the defeciency also. All were
documented cases that eventually had to be treated (successfully) with
B12 supplements. I also can attest that many other health prof's (both
traditional and alternative) have seen an increase in this over the last
few years.
Most of the following comes from the following source with some of my
own additions:
Messina V, Messina M. The Dietitian s Guide To Vegetarian Diets: Issues
and Applications. Gaithersburg, Maryland: Aspen Publishers, Inc.;
1996:161-173.
ON B12:
The natural source of this vitamin in nature is by synthesis of
microorganisms (2). Therefore it is not found in plants except when
they may be contaminated by microorganisms. Fruits, vegetables and
grains are usually devoid of vitamin B12. Small amounts of B12 have
been found in legumes (6), which contain microorganisms, and in some
foods that may have been contaminated. These foods may provide the only
B12 for vegans. Rich sources of B12 are organ meats. Moderately high
amounts are found in milk, seafood, and egg yolk. Moderate amounts are
found in milk products, cream cheese, cheddar cheese, and cottage
cheese. The enzymatically active forms of B12 foods, which are
generally attached to polypeptides, are the dominant forms found in
foods.
Deficiency
Approximately 95% of the known cases of B12 deficiency occur in
individuals who are not able to absorb the vitamin because of a lack of
IF or because of a reduction in gastric acid or in the gastric enzymes
required to cleave B12 from the proteins in food (6). Actual reported
cases of B12 deficiency due to inadequate intake are rare, although they
do exist (5).
Vitamin B12 deficiency causes red blood cells to increase in size
because cell division is inhibited but the cell itself continues to
grow. This is the same type of megaloblastic anemia that is seen in
folate deficiency. B12 deficiency is also associated with
demyelinization of peripheral nerves, the spinal cord, the cranial
nerves, and the brain, resulting in nerve damage and neuropsychiatric
abnormalities. The symptoms include decreased sensation, difficulty in
walking, loss of bladder and bowel control, optic atrophy, memory loss,
dementia, depression, weakness and psychosis. Nerve damage from B12
deficiency can be irreversible (2).
High levels of folate can mask B12 deficiency to some degree, since
normal red blood cells continue to be produced even in the presence of
B12 deficiency (4). In this case, the B12 deficiency may not be
detected until the more serious and irreversible nerve damage is
observed. This may be of some concern for vegans because their intake
of B12 may be low and their intake of folate is generally quite high.
Non-Animal Sources
Non-animal foods that have been reported to contain B12 include
fermented foods (such as tempeh), sea vegetables, algae, spirulina,
various greens, and legumes (8). Rainwater has also been reported as a
source B12 (9). One analysis of over 40 plant foods found that most did
not contain B12 (10). Tiny amounts (.02 to .50 ug/100g) were found in
barley malt syrup, sourdough bread, parsley and shitake mushrooms. Only
the algae and spirulina contained considerable amounts. Herbert, et
al., and Herbert and Drivas found that the B12 in spirulina is mostly
analogues (11).
Dagnelie et al reported that the consumption of nori, spirulina, kombu,
whole-meal sourdough bread, and barley malt syrup did not improve mean
corpuscular volume or mean corpuscular hemoglobin mass despite an
increase in B12 plasma volume (12). This suggests that the B12 in these
foods is mostly analogues. Some other studies have shown that the
consumption of these sea vegetables has resulted in higher serum plasma
B12 levels in individuals (33). This suggests that sea vegetables when
consumed in reasonable amounts may provide some active B12, though not
enough to meet vitamin B12 needs. The presence of analogues is an
important consideration because some studies have found that high levels
of cobalamin analogs are associated with neurological abnormalities in
cobalamin deficiency. High levels of analogs may actually increase the
risk of B12 deficiency as they may compete with true vitamin B12 in the
body (6).
Legumes, such as soybeans, posses root nodules that can be inhabited by
bacteria (8). These bacteria may produce small amounts of active
vitamin B12 and analogue. The USDA, however, indicates that legumes
contain no vitamin B12. Therefore, these foods should not be considered
as a reliable source of vitamin B12.
Bacteria in the digestive tract of humans produce considerable
amounts of active vitamin B12 (14), however, it is not exactly clear at
the present time on the extent that this vitamin B12 is available for
absorption. Most of this vitamin B12 is produced to far down the colon
to be absorbed, and most of it ends up in the feces (15). Smaller
amounts of vitamin B12 are produced in the intestines and there is
evidence that this can be absorbed (14). This intestinal synthesis is
considered to be one of the reasons why vitamin B12 deficiency is
uncommon among the vegetarian population. Vegetarian diets may also
modify the environment of the intestines, favorably modifying the types
of microorganisms in the gut. Vegetarians have a larger growth of
microflora then nonvegetarians. Intestinal synthesis of vitamin B12 has
been proposed as one of the reasons for why vitamin B12 deficiency is
uncommon among the largely vegetarian population of India (16).
Additionally, the oral cavity does produce vitamin B12 in small amounts
(6). Whether this is true vitamin b12 or analogues has not been
distinguished yet. Either way, the quantity produced is not sufficient
to meet the daily needs, though, it may contribute to the daily
intake.
B12 Status and Vegetarians
Approximately 95% of the known cases of vitamin b12 deficiency
occur in individuals who are not able to absorb this vitamin because of
the lack of IF or because of a reduction in gastric acid or the gastric
enzyme required to cleave the vitamin from the proteins in food (5).
Actual reported cases of symptomatic vitamin B12 deficiency due to
inadequate intake are rare, thought they do exist. This is an important
issue amongst the vegan population. They are considered at high-risk for
vitamin B12 deficiency since they consume no animal products in their
daily diet.
There are several possible explanations for why there is a scarcity
of published vitamin B12 deficiency among vegans (6): (a) there are
relatively few studies of long-term vegans who do not use supplements or
fortified foods; (b) drinking water contaminated with vitamin B12
producing bacteria may be a significant source, particularly in
developing countries.
Although overt symptoms of deficiency are rarely observed, plasma
levels of vitamin B12 tends to be lower in vegans and
lacto-ovo-vegetarians then in the general population. Ellis and
Montegriffo studied 26 vegans, including 7 of whom did not take any
supplements and found no blood abnormalities related to a deficiency
state, although their serum levels were low (12). Four of the subjects
had been on the diet for over 13 years without any supplements and had
normal vitamin B12 serum levels.
In an Israeli study, 4 vegans with low blood levels of vitamin B12
had no hematological abnormalities but complained of weakness, fatigue, and
poor mental concentration (6). Upon administration of B12, their blood
levels increased and their symptoms improved. Another study of Thai
vegetarians found their blood levels to be one tenth those of the
omnivores, though, all the vegans appeared healthy, and none displayed
any symptoms of vitamin b12 deficiency or megaloblastic anemia (6).
This was also the case in an Indian study, where it was found that, low
blood levels was found amongst the vegetarians, none of them displayed
any signs or symptoms of vitamin B12 deficiency (18).
In another study of vegans, among those who did not use supplements,
vitamin B12 levels decreased the longer the subject followed the vegan
diet. Crane et al. studied 78 subjects who had been vegan for 12 - 340
months and who reported consuming no vitamin B12 supplements or
fortified foods for at least one year prior to the study (19). Sixty
percent had blood levels below the normal level and four subjects had
indications of abnormal red blood cell synthesis. In comparison, the
subjects who used fortified foods had serum levels above normal.
Summary
Although vitamin B12 is an important tissue in vegan nutrition, it
is an easily resolved one. Regular use of fortified foods provide adequate
B12 for most vegans. Vitamin B12 supplementation is another option for
vegans. Some supplements of vitamin B12 provide as much as 500
ug/dose. At these high levels absorption efficiency decreases
remarkably. Therefore, recommendations for proper supplement use would
include the use of smaller doses several times a week. Recent studies
indicate that B12 supplements need to be chewed before swallowing in
order to be absorbed, allowing the B12 to combine with the R factor.
Overall, there are very few actual cases of true vitamin B12
deficiency among vegans. There are several explanations for this
including: (a) few studies of long-term vegans have been conducted, (b)
vitamin B12 requirements are small, and storage capacity for this is
considerable so that deficiency may take years to manifest, (c) the body
conserves vitamin B12 through an efficient enterohepatic circulation so
little vitamin B12, (d) plant foods may be contaminated with vitamin B12
producing bacteria, and, (e) vitamin B12 production in the human
digestive tract in both the oral cavity and intestines may contribute to
B12 intake. While all these factors may contribute to the B12 status of
vegans, it is possible that none are sufficiently adequate or reliable
enough to promote satisfactory vitamin B12 status. It is possible that
most or all Western vegans whose diets are unsupplemented may eventually
develop vitamin B12 status.
References
1. Shorb MS. Notes on the history of vitamin B12. Science.
1988,107:397-399
2. Herbert V, Das KC. Folic acid and vitamin B12. In: Shils ME, Olson
JA, Shike M., eds. Modern Nutrition in Health and Disease. 8th ed.
Philadelphia: Lea and Febiger, 1994:402-425.
3. Dolphin D. (ed.). B12. Vols 1 and 2. New York, John Wiley & Sons,
1982.
4. Bender DA. Nutritional Biochemistry of the Vitamins. New York:
Cambridge University Press, 1992:269-317.
5. Herbert V. Vitamin B12. In: Brown ML, ed. Present Knowledge in
Nutrition. 5th ed. Washington, DC: Nutrition Foundation; 1984:347-364.
6. Messina V, Messina M. The Dietitian s Guide To Vegetarian Diets:
Issues and Applications. Gaithersburg, Maryland: Aspen Publishers,
Inc.; 1996:161-173.
7. Herbert V. Recommended dietary intakes (RDA) of vitamin B12 in
humans. Am J Clin Nut. 1987;45:671-678.
8. Long A. Vitamin B12 for vegans. Br Med J. 1977;2:191. Letter
9. Parker PC. Rains as a source of vitamin B12. Nature.
1968;219:617-618.
10. Van der Berg H, Dagneli PC, Van Staveren WA. Vitamin B12 and
seaweed. Lancet. 1988;1: 242-243.
11. Herbert V, Drivas G. Spirulina and Vitamin B12. JAMA.
1982;248:3096-3097.
12. Dagnelie PC, van staveren WA, van der Berg H. Vitamin b12 from
algae appears not to be bioavailable. Am J Clin Nutr. 1991;53:
695-697.
13. Rauma A-L, Vitamin B12 status of long-term adherents of a strict
vegan diet is compromised. J Nutr. 1995;125:2511-2515.
14. Alberts MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human
small intestinal bacteria. Nature. 1980;283:781-782.
15. Armstrong BK. Absorption of vitamin B12 from the human colon. Am
J Clin Nutr. 1968;21:298-299.
16. Bhat P, et al. Bacterial flora of the GI tract in southern Indian
control subjects and patients with tropical sprue. Gastroenterology.
1972;62:11-12.
17. Ellis FR, Montegriffo VME. Veganism, clinical findings and
investigations. Am J Clin Nutr. 1970;23:249-255.
18. Mehta BM, Rege DV, Satoskar RS, Serum vitamin B12, and folic acid
activity in lactovegetarians and nonvegetarian healthy adult Indians.
Am J Clin Nutr. 1964;15:77-84.
19. Crane MG, Sample C, Patchett S, Register UD. Vitamin B12 status in
total vegetarians (vegans). J of Nutr Med . 1994;4:419-430.
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