Newsgroups: sci.med.nutrition From: firstname.lastname@example.org (Ted Wayn Altar) Subject: Vitamin B12 and Vegans Message-ID: email@example.com Organization: Simon Fraser University, Burnaby, B.C., Canada Date: Thu, 14 Jan 1993 23:41:30 GMT Lines: 546
Michael Traub wrote:
B12 deficiency is more common in omnivores than in vegans.
Martin Hulsey replied:
Do you have a peer-reviewed reference from a bona fide nutrition
journal that says this? I have a couple that say quite the opposite.
I have to agree with Martin in that I've not heard of this before either, but I have seen claims to the opposite. In a trivial sense, of course more omnivores incur B12 deficiency problems simply because there are more of them. Of course, this is not what is at issue. What we need are accurate incidence rates (and ideally breakdowns of the various causes of B12 deficiency) and this would require very large samples of people.
FACTORS THAT AFFECT DIETARY B12 NEEDS
Of course, maybe we need to qualify which "vegans" are clearly at risk and which one's might "theoretically" be at risk. First, consider some of the factors that are known to increase one's need for B12:
(1). Meat or other animal products and refined carbohydrates (sugars) when used generously may more than double B12 needs.
(2). Persons who use drugs, chemical, or beverages which destroy B12 (e.g., tobacco, alcohol, caffeine, etc.)
(3). Megadoses of vitamin C may produce B12 deficiency by destroying the cobalamins during transport through the gastrointestinal tract (Hines, 1975). Quantities more than 1/2 of a gram can destroy 50% to 95% of B12 in the food.
(4). Oral contraceptives are used (affects the B12 binders of the blood).
(5). egg albumin and egg yolk decreases B12 absorption
(6) intestinal parasitism (e.g., tapeworms) and explosively growing bacterial floras can effectively compete with the host for the vitamin
Given these factors that do increase need, it is apparent that meat eaters do need more B12, but presumably this is adequately compensated for by the fact that they consume more dietary B12. It is of course possible that the compensation may not be great enough. Rather than only speculate, however, upon a "theoretical" deficiency, it would be best to have in hand some actual actuarial data documenting from large samples the relative rates of B12 deficiency disease among omnivores as compared to vegans. So far, I've not seen any such actuarial data compiled. But this is understandable when we keep in mind that B12 deficiency is actually rare and of the cases occurring 95% of those cases are not due to a simple dietary deficiency but rather to physiological absorption/utilization problems.
B12 DEFICIENCY AMONG VEGAN INFANTS AND CHILDREN
There are, however, amply studies (see Chanarin et al., 1985; Dagnelie et al, 1989a; Dagnelie, 1989b) upon some groups of vegans whose young children and infants are documented to show an higher than expected incidence of the signs and symptoms of B12 deficiency (see references below). This concern for the children of some fad vegetarians that should be seriously noted. There is enough evidence (see references below) to here warrant concern that some vegan groups do incur a risk of B12 deficiency among their young children. In particular, vegetarian groups prone to certain "fad" vegetarianism like that of macrobiotic or crudivore diets, seem to sometimes (again, not consistently) have a higher incidence of B12 deficiencies among their young children.
Why certain vegetarian diets or practices seem to incur this problem is not yet understood. The heavy use of nori, for instance, could be one explanation. The problem with algae sources like spirulina or nori is not only that they are low in what is being NOW measured as B12 by newer methods (see Herbert, 1988) but that it may not be a true B12 but possibly contains what has been referred to as noncobalamin analogues of B12 that might actually interfere with the absorption of true B12. In any case, "B12" from spirulina or nori, if it is true B12, is simply NOT bioavailable (see Dagnelie, 1991). Another possible explanation would be the "explosive" growing of bacterial floras that can be stimulated by certain very high fiber diets (which would characterized the extreme macrobiotic diets of eating only cereals, particularly rice, which are high in the slowly fermentable fibers that most readily promote microbe proliferation)
In any case, to err on the side of caution, certainly lactating vegetarian women and young vegan children should certainly take some supplements. The Nutrition Standing Committee of the British Paediatric Assoc recommended in its special report on vegetarian weaning (ARCHIVES OF DIS. IN CHILDHOOD, 1988, 63:1286), for instance, recommended B12 supplements at weaning and for breast feeding vegan mothers.
RECOMMENDED AMOUNTS OF B12
Now, before we consider the more controversial question about whether or not adult vegans have an higher incidence of B12 deficiency disease than omnivores, it might be helpful to keep in mind some of what is known about about B12 needs.
Now, the amount of B12 actually needed by the body is incredibly small and the RDA level is of course more than you need, due to considerations for a safety margin but also because of the measurement problem for small amounts of B12 and the consequent assessment of now much B12 is really necessary for human beings. The National Research Council recommends 3 micrograms (3 millionths of a gram) per day to meet the body's needs. Victor Herbert, who is probably the leading authority on B12, suggests that 1 microgram would be a better RDA, and he puts the actual requirements of *absorbed* B12 to be round .1 microgram/day (hence, the NRC recommendation may in practice be some to 6 to 30 times greater than our actual requirement).
Absorption of the vitamin also decreases with increased intake. At low levels of intake the mean absorption is 70% (even higher for people with low serum levels of B12), but at high intake levels the absorption rate drops to about 16%.
The fact of the matter is that you need very little and your body can store the stuff for 3 to 5 years. Hence, you simply don't need to consume B12 every day. Another point maybe to keep in mind is that researchers really don't know how much low levels of B12 is in our foodstuffs since their is not yet a sensitive enough assay for trace amounts of B12.
The main rout of loss of bodily B12 in the bile, while most of the bile is effectively reabsorbed (more than 90%), some is not thereby making for a loss of B12 (about .1 microgram/day). Because vegans generally eat less fat and no cholesterol, their production of bile is less and it is therefore likely that their need for B12 replacement would also be less.
VEGAN SOURCES OF B12
It is true that cultured sources may have little or no B12, but this depends on the culturing process. Nutritional yeast, for instance, if cultured under controlled conditions so stringently that no bacteria is allowed to grow along with the yeast, then indeed there will be no B12, since the only source in nature is from bacteria (incidentally, I have been told that the gene for B12 from bacteria could theoretically be cloned onto nutritional yeast so that we could then not only a tasty yeast but one with more than enough B12). Some nutritional yeasts, may use a B12 rich feed for the yeast, in which case the yeast would then be a good source of B12.
It has been reported that B12 is to be found on the roots and stems of tomatoes, cabbage, celery, kale, broccoli, and leeks. Victor Herbert, however, found that "well washed" plant foods contain no B12 except for trace amounts in some rhibozium- bacteria-containing root nodules.
Some recent dietary intake studies of vegans showed them to be consuming, (including B12 from fortified foods like certain soya milks and margarines) an average intake of 1.2 -1.8 micrograms (Carlson et al., 1985; Sanders et al., 1987; Rana et. al.). In a Swedish study where fortified foods were not used, the average intake of .35 micrograms was recorded (Abdulla et al., 1981). Gill Langely (1988), in his fine survey of the research on vegan nutrition, reports a study indicating British vegan pre-school children had a mean intake of 280% of the British RDA (but 5 did have intakes less than the recommended intake (Sanders, 1981). An U.S. vegan community that used supplemented soya milk and yeast, had mean intakes of 15 micrograms or about 660% of US RDA for children. In none of the above groups were any clinical signs of deficiency found.
Maybe a more important consideration than what is to be found in our foods is that much vitamin B12 is actually produced by the body itself. Bacterial flora in the gut, but also bacterial growth in the mouth, around the teeth and gums, in the nasopharynx, around the tonsils and tonsillar cypts (another reason not to remove tonsils if possible), in the folds at the base of the tongue and even in the upper bronchial tree can produce B12.
It is known that the B12 is produced in huge amounts in the colon (5.0 micrograms/day), though it doesn't seem that it can be absorbed through the walls of the colon. The small intestine, however, can absorb B12 and indeed some B12 producing bacteria is to be found there. It is possible that enough intrinsic factor enters the small intestine still sufficiently active to bond with B12 for absorption. It is also possible that vegan physiology enables a more ready absorption (or lower need?), than theoretically expected. Who knows? What we do know that people's ability to absorb many nutrients increases as one's need for those nutrients increases. For example:
". . . vegetarians appear to "undergo physiological adaptation enabling them to make somewhat better utilization of iron than would be expected from iron bioavailability studies involving the feeding of vegetarian diets to omnivores or involving the testing of particular components characteristic of vegetarian diets with omnivore subjects." (from Kies & McEndree "Vegetarianism and the bioavailability of iron" in Kies (ed.) NUTRITIONAL BIOAVAILABILITY OF IRON, 1982).
Hence, we must exert some caution in extrapolating the nutritional needs and adaptive capacities of omnivores to that of vegans. Better, therefore, to look at the DIRECT evidence of vegan health or deficiency.
ARE ADULT VEGANS AT A GREATER RISK OF B12 DEFICIENCY?
Vegetarians who are not vegans but still consume milk products and eggs, probably not need to worry about B12 deficiencies.
Indeed, it is not evident that sensible adult vegans actually suffer from a greater incidence of B12 deficiency than do omnivores. If one eats a variety of food products, consumes fresh vegetables and is not on antibiotics, then the B12 being produced by bacteria in the gut and the trace amounts from foods may well be sufficient. The direct evidence for this comes from those studies that have actually tested vegans to see if B12 deficiencies turn up. In general, the results uniformly indicate that even in the case of those vegans who for decades have not taken any supplements they still appear to have adequate B12 levels. While the serum levels of B12 tend to be lower than that of an omnivorous control group, hematologic evidence of vitamin B12 deficiency is not present.
As Gill Langely reports:
Accepted normal serum levels fall within a wide range -- from 100-900 pg/ml. Values below 80pg/ml suggest a possible deficiency of B12 while between 80 and 140pg/ml there may or may not be symptoms of deficiency. LOWER THAN NORMAL SERUM LEVELS OF THE VITAMIN ARE NOT, OF THEMSELVES, INDICATIVE OF A DEFICIENCY. As already mentioned, vegans of up to 20 years standing with no obvious source of the vitamin in their diets only very rarely have clinical symptoms of deficiency. Although their serum level of B12 does fall over a number of years it often stabilizes at about 100pg/ml. Vegans who take supplements or fortified foods generally have higher serum levels of the vitamin, while VEGAN MACROBIOTICS OR SMOKERS MAY BE PREDISPOSED TO B12 DEFICIENCY.
Consequently, surveys of vegans document a wide variation of serum levels of B12. On report (Ellis, 1967) mentions values between 30 and 650 pg/ml with a mean value (of 20 subjects) of 236pg/ml, compared with a range of 120-740pg/ml and a mean serum value of 441 pg/ml in matched omniovre control subjects. There was NO CLINICAL EVIDENCE OF B12 DEFICIENCY EVEN IN THOSE VEGANS WITH THE LOWEST SERUM LEVELS, although one 80-year-old subject who had been a vegan for only 2 years had pernicious anemia. Three vegans who had been on the diet for 17 years without taking supplements were healthy, with serum B12 levels of 150, 375 and 450pg/ml, and normal amounts of haemoglobin in the blood.
Haematological measurements (Sanders it al, 1978) of 34 vegans who had been on the diet for between one and 30 years revealed a range of serum B12 levels from 94-675pg/ml -- all ABOVE the value of 80pg/ml at which deficiency symptoms can be expected. The majority of subjects took B12 tablets or food fortified with the vitamin, and those who did had higher amounts in their blood. THE SERUM LEVELS OF THREE SUBJECTS WHO HAD BEEN VEGAN FOR 6-13 YEARS (LONG ENOUGH THEORETICALLY TO EXHAUST LIVER STORES OF B12) WITH NO OBVIOUS DIETARY SOURCE OF B12 WERE ALSO ADEQUATE, at 120-230pg/ml. All the vegans were healthy, none showed symptoms of B12 deficiency and all had normal haemoglobin values. The same report lists other surveys of vegans which have failed to show symptoms of dietary deficiency of B12. [emphasis his]
Given what conservative authorities have to say in theory about B12 (especially those that would undertake an analysis of the composition of a vegetarian diet), we should expect to see a greater incidence of B12 deficiency in vegans than in non-vegans, yet there is no such difference as far as I know.
Of course, people will cite some case studies of some unfortunate vegans but such case studies are limited in that we don't have a proper comparison with non-vegans and by now it should be apparent that many other causes besides dietary deficiency can be at fault. If one looks at these case studies closely, the individuals are often reported as having other deficiencies thereby undermining the very point that such cases might thought to have illustrated in the first place.
What is interesting is that B12 is so extremely rare that even single case studies get published, but the generalizability of such case-studies to the general population of vegans is not to automatically be undertaken. More evidence than this is needed, especially when the confound of physiological aborption/utilization problems are often not properly ruled out in these case studies.
CAUSE FOR VEGAN PANIC?
Let it again be said, however, that B12 deficiency is "rare" among vegans and that over 95% of deficiency problems are not due to a simple intake inadequacy but are due to an malabsorption problem. the development of a serious B12 deficiency is not a simple or well understood matter but it is known that absorption and conservation of B12 in the body is more important than how much is to be found in the diet.
known causes of malabsorption are a lack of intrinsic factor (e.g., due to pernicious anemia, destruction of gastric mucosa, etc.), removal or disease of the second portion of the ileum, competition for B12 by microorganisms or intestinal parasites, toxic substances, etc.
beside malabsorption, there are also possible problems (see herbert, 1973) in utilization (e.g., enzyme deficiencies, liver or kidney disease, etc), increase loss (e.g., renal disease) or for an increase requirement (e.g., hyperthyroidism, lactose intolerance).
still, if one has an absorption, loss, or increase need problem, then presumably when little B12 is available in the diet then still less is going to be assimilated. now, what can vegans do to prevent a B12 deficiency?
HOW VEGANS MIGHT INCREASE THEIR B12 INTAKES
Fresh garden pricked vegetables, particularly root vegetables, that are not overly scrubbed cleaned or pealed will have some b- 12 on their surface. Boiling such vegetables and then throwing out the water would make for a loss of this B12.
Since B12 is predominantly produced by bacteria (no animal produces its own), then foods grown in soils where the bacteria flora is rich would presumable have more B12 on their surface. Hence, organically grown foods will probably be richer in B12.
There is now some recent evidence (Combs, 1991) that some peas and bean actually produce their own B12. It was previously thought that the only source in nature was bacteria. This would suggest that such peas and beans would have their B12 throughout rather than just on the surface. Still, this probably will not suffice as a single plant source to provide sufficient B12.
A simply but useful recommendation is to chew one's food properly and leave plenty of time between meals helps absorption. The r- binders in saliva help to hold onto the B12 in the food until it reaches the small intestine where it absorbed (Fleming, 1978).
Multivitamin preparations containing B12 is probably not a good idea. Besides consuming so-called vitamin "d" which most people do not need and which has been implicated in helping to cause arteriosclerosis and osteoporosis, these preparations contain breakdown products of B12 that can actually have an anti-B12 effect. Hence, multivitamins may contribute to the very deficiency that they were supposed to correct. Victor herbert (1962), the leading authority on B12, reported that all of the 10 multivitamin-mineral products that he tested showed anti-B12 breakdown products. Tests for B12 in the blood unfortunately cannot discriminate between the true vitamin B12 and its breakdown products.
For healthy adult vegans I do think we should be careful about recommending routine B12 supplements. Even though complete absorption is not likely, the dosages are probably still too high (1200 mcg). There is some case studies and experimental evidence that an excessive B12 consumption encourages cell division in general and certain tumor cells in particular (bergevin et al., 1976; chauvergne, 1970).
In general, use of B12 supplements should be certainly be considered by pregnant and lactating women, young infants and children, the elderly and vegans not in good health or who still smoke. Serum levels of B12 are lower for smokers than non- smokers (this may be an effect of the cyanide content of tobacco smoke, which the body attempts to detoxify by a means that unfortunately uses up the stores of B12).
Non-smoking, healthy adult vegans who eat sensibly, are not on medications (e.g., antibiotics) and who do not daily drink alcohol probably do not need to take supplements. If such vegans are going to take supplements, then they should probably not take them on regular basis since the doses are too high.
Individuals even on conventional diets (diets high in fat and animal protein which increase the need for B12) still only need about 1 mcg per day according to Victor Herbert (recent revision of RDA recommendations has lowered the amount from 3 mcg/day to 2 mcg/day). Maybe half of a typical 1000 mcg pill about once month would be more than sufficient. Finally, vegans and non-vegans should make sure that their B12 supplements are derived from bacteria cultures and do not contain spirulina or nori.
If one has been a vegan for a many years, it might be a good idea to have one's serum B12 levels checked. The normal range is about 150-750 pg/ml according to the merck manual. Others put it at 100-900 pg/ml. There is no exact cutoff. Vegans, of course, will have levels at the low end but this by itself is not a cause for alarm. After all, the "normal" range is based upon research from an omnivorous population and vegans do have a lower need for B12 and are more efficient at preservation of extant stores. indeed, it could be argued that the "true normal" range might well closer to that of vegans. The "ideal" physiological functioning has yet to be determined, but we do know that almost all investigators reporting on vegans report them as being above average in health and more active.
Look, I don't wish to deter any adult vegans from taking B12 supplements. They certainly can't do any harm and one doesn't have to take them that often. Better to err, even if it is needless error, on the side of caution. Also, there are now plenty of B-12 fortified foods.
REFERENCES 1: General
Abdulla et al. (1981). Nutrient intake and health status of
vegans Chemical analyses of diets using the duplicate portion sampling technique. AM. J. CLIN. NUTR., 34:2464-77.
Akers, Keith (1989). A VEGETARIAN SOURCEBOOK: THE NUTRITION,
ECOLOGY, AND ETHICS OF A NATURAL FOODS DIET.
Bergevin et al, (1976). Pernicious anemia terminating in acute
myeloblastic leukemia. SOUTHERN MEDICAL JOURNAL, 69:110.
Carlson et al. (1985). A comparative evaluation of vegan,
vegetarian and omniovre diets. J. PLANT FOODS, 6:89-100.
Chauvergne, J. (1970). The risk of administering vitamin B12 to
cancer patients. SEMAINE DES HOSPITEAUX PARIS 46:2170
Combs, Gerald (1991). VITAMINS: THEIR ROLE IN NUTRITION &
Dagnelie et al. (1991). Vitamin B12 from algae appears not to be
bioavailable. AMER. J. OF CLINICAL NUTRITION, 53:695.
Fleming, A. (1978). Serum vitamin B12 levels and vitamin B12
binding proteins of serum and saliva of healthry Nigerians and Europeans. AMERICAN J. OF CLIN. NUTRITION, 31:1732.
Hector & Burton (1988). What are the psychiatric manifestations
of vitamin B12 deficiency? JOURNAL OF THE AMERICAN GERIATRICS SOCIETY. 36(12):1105-12,
Herbert, V. (1962). Harmful B12 breakdown products in
multivitamins? MEDICAL WORLD NEWS, (Sept. 28):12-13.
Herbert, V. (1973). The five possible causes of all nutrient
deficiency: Illustrated by deficiencies of vitamin B12 and folic acid. AMER. J. OF CLIN. NUTRITION, 26:77.
Herbert, V. (1988). Vitamin B12: plant sources, requirements,
and assay. AMER. J. OF CLINICAL NUTRITION, 48(3):852.
Hines, J. (1975). Ascorbic acid and vitamin B12 deficiency. J.
OF AMER. MED. ASSOC., 234(1):24.
Thrash & Thrash (1982). NUTRITION FOR VEGETARIANS, 1982.
REFERENCES 2: Group comparison studies involving adult vegetarians.
Bar-Sella et al. (1990). Vitamin B12 and folate levels in long-
term vegans. ISRAEL JOURNAL OF MEDICAL SCIENCES. 26(6):309
Ellis & Montegriffo (1970). "Veganism, clinical findings and
investigations. THE AMER. J. OF CLIN. NUTR., 23(3):249.
Ellis & Mumford (1967). The nutritional status of vegans and
vegetarians. PRC. NUT. SOC., 26:205-12.
Ernst et al. (1986). Blood rheology in vegetarians. BRIT. J. OF
Rana et al. (1986). Taurine concentratins in the diet, plasm,
urine and breast milk of vegans compared with omnivores. BR. J. NUTR., 56:17-27.
Sanders et al. (1977). Haematological studies on vegans. BRIT.
J. OF NUTR., 40:9
Sanders, T. (1978). The health and nutritional status of vegans.
PLANT. FDS. MAN, 2:181-93.
Sanders & Purves (1981). An anthropometric and dietary
assessment of nutritional status of vegan preschoold children. J. HUM. NUTR., 35:349-57.
Sanders et al. (1987). Blood pressure, plasma renin activity and
aldosterone concentration in vegans and omnivore controls. Hum. Nutr.: Appl. Nutr., 41A:204-11
Smith (1962). Veganism, a clincal survey with observations of
vitamin B12 metabolism. THE BRIT. MED. J, 1(June 16):1655.
Wokes et al. (1955). "Human dietary deficiency of vitamin B12.
THE AMER. J. OF CLIN. NUTR., 3(5):375
REFERENCES 3: Studies involving some vegetarian children indicating the presence of B12 deficiency.
Chanarin et al. (1985). Megaloblastic anaemia in a vegetarian
Hindu community. LANCET, 2:1168
Dagnelie et al. (1989a). Nutritional status of infants on
macrobiotic diets aged 4 to 18 months and matched omnivorous control infants: a population-based mixed-longitudinal study. Weaning pattern, energy and nutrient intake. EUR. J. CLIN. NUTR., 43:311.
Dagnelie it al. (1989b). Increased risk of vitamin B12 and iron
deficiency in infants on macrobiotic diets. AM. J. CLIN. NUTR., 50:818.