hello misha,
The following is my translation of an article written for the german
natural hygiene society by dipl. oec. troph. petra luehrmann and
prof. dr. rer. nat. claus leitzmann from the institute for
nutritional science at the justus liebig university in giessen,
germany (any translation errors found are my own "copywrongs",
but you may keep them anyway - hoping there are not too much).
This article, published in December 1993 and written by one of
germany's leading nutrition scientists (i think, it's correct to
say that leitzmann in germany is accepted as THE nutrition
expert), should help to clear up some of the "myths" being
bandied around on this vitamin:
--- VITAMIN B12 - THE CURRENT STATE-OF-THE-ART OF RESEARCHWhat is vitamin B12?
Vitamin B12 is a group name for a number of closely related chemical compounds which have a molecular structure known as a corrin. Of all the vitamins, B12 has by far the most complicated structure. It is the only known nutrient which contains the trace element cobalt. When exposed to light, oxygen or acidic or alkaline conditions, it slowly looses its vitamin properties. On the other hand, it is relatively heat-resistent. The average loss as a result of cooking, for example, is said to be about 12%.
The molecular structure of vitamin B12
Whilst I can supply anyone interested with a molecular diagram showing the structure, it is only really important in this connection to note that there are a number of substances with a similar structure to B12 but which lack certain atoms or carry additional side-chains. Such molecules, known as B12-Analoga, are totally ineffective as substitutes for the real thing.
How is vitamin B12 taken up in the body?
The resorption of vitamin B12 is a fairly complicated process and takes place in the lower part of the small intestine. Resorption is only possible with the aid of a specific protein known as intrinsic factor which is produced by the gastric glands in the stomach lining.
How much vitamin B12 do we need?
Vitamin B12 is an "essential", in other words it is vital to our health and wellbeing and can only be obtained from outside food sources. It is involved as a co-factor in numerous enzymatic reactions in the body. The recommended doses vary depending on your scientific source of information. A number of research projects have revealed, however, that 1 ug (meaning a millionth of a gram..as I can't reproduce the little tail on the bottom left-hand corner of the "u" in "ug" in here) of resorbed B12 is sufficient to top up and maintain the body reserves and prevent any signs of a deficiency. However the B12 contained in foodstuffs is by no means fully resorbed: Strange but true, the less B12 a meal contains the higher the percentage actually resorbed by the body. An intake of 0.1 ug results in a resorption of around 77%, 1 ug 56% and 50 ug only 3%. In other words, the body only resorbs about half of the B12 in a meal.
The German Society for Nutrition (Deutsche Gesellschaft fuer Ernaehrung - DGE) recommends an intake of 3 ug vitamin B12 per day. The U.S. Food and Nutrition Board, on the other hand, says that a daily intake of 2 ug is sufficient. The Word Health Organisation is convinced that 1 ug per day is enough. To top it all, the well-known North American nutritionist Victor Herbert claims that 0.2 - 0.25 ug are all we need to cover our daily requirement. Whilst these differing recommendations may well be a result of the common practice of adding a "safety bonus" to "cover all eventualities", they certainly seem to reflect the general uncertainty as to how much B12 we really do need to take up each day.
Which foodstuffs contain vitamin B12?
Vitamin B12 can only be produced by microorganisms and is practically only found in animal-based foods. Liver generally provides the highest quantity of B12, although meat and meat products, as well as fish, eggs and dairy products, are also rich in B12. Vegetables, on the other hand, can only contain B12 if they have come into contact with microorganisms. A look through the scientific literature shows the following plant-based foods as containing B12:
- Vegetables containing lactic acid, e.g. sauerkraut (fermented white cabbage)
- Fermented soya products, e.g. Tempeh, Natto, Miso etc.
- Marine plants, e.g. algae
- Yeasts and products manufactured from yeasts such as bread and beer
- Fermented cereal products
- The leaves of alfalfa shoots
- Root vegetables
The info in publications before about 1990 on the B12 content of various foodstuffs is both contradictory and should be taken with a piece of salt in view of the rather unreliable methods in general use before this date (microbiological tests and non-specific radiochemical methods). They also included the B12-Analoga, i.e. those molecules mentioned above which look like but do not produce the same effects as the real thing in the human system. In recent years a new method has been developed which only identifies the real B12 and thus gives a much more accurate picture of the B12 content of various foodstuffs (it is a radiochemical method which uses intrinsic factor to bind the genuine, active B12). Using this method it was discovered that fermented soya products, yeasts and blue algae of the genus spirulina contain practically no real B12 whatosever. The only plants found to contain active B12 were legumes (largely because a number of species of soil bacteria live in their roots) and several species of marine plants. The considerable differences between animal and plant foods can be seen in the table following:
Active vitamin B12 Content per 100 g Foodstuff
Very high (over 10 ug) Innards (livers, kidneys, hearts), mussels, oysters
High (3 - 10 ug) Shrimps, sardines, mackerel, herings
Medium (1 - 3 ug) Cheeses (Camembert, Emmental, Edam, Tilsiter), eggs
Low (less than 1 ug) Milk, curd, cottage cheese, yoghurt, root vegetables, legumes, marine plants
Undetectable Yeasts, fermented soya products (e.g. Tempeh, Natto, Miso), blue algae (genus spirulina)
How do the symptoms of a B12 deficiency look like?
A B12 deficiency effects virtually every body cell. A continuous deficiency leads to megaloblastic anaemia (abnormally large blood cells in the bone marrow). The symptoms are a loss of appetite, weight-loss, a global feeling of weakness, pale skin and a smooth tongue with a burning sensation. In addition, a B12 deficiency can also lead to the degeneration of various parts of the spinal cord and therefore cause permanent damage to the nervous system (the symptoms can range from increased reflexes, or the loss of reflexes, and can later lead to uncoordinated movements and even paralysis). A B12 deficiency in children can seriously retard their development.
A nutrition-based deficiency is extremely uncommon. The average intake in Germany, for example, is well over the recommended requirement (females 4.1 microgr per day and males 5.8 microg per day). The most common cause of a deficiency is impaired resorption. This is the result of an illness in the small intestine (e.g. Coeliac disease or sprue, which in turn are caused by the excessive consumption of cereal-based products containing gluten) or an impaired synthesis of the intrinsic factor necessary for the resorption of B12. The production of intrinsic factor can be impaired by the surgical removal of part of the stomach or through an inflammation of the stomach lining (gastritis).
The B12 level in the blood serum is generally used to assess the level in the body as a whole. You are said to have a problem if the concentration is found to be smaller than 150 pg/ml. However a low serum concentration does not necesarily point to a clinical deficiency.
Research has shown that the serum concentration is generally lower when less animal-based foods are consumed. Vegetarians and vegans almost always have lower readings than lacto or ovo-lacto vegetarians (ovo = eggs, lacto = dairy produce). The later, on the other hand, generally have lower readings than the those with a mixed diet of both animal and vegetable foodstuffs. Lacto and ovo-lacto vegetarians generally take in around 2 microg of B12 per day (resulting from the consumption of milk and milk products and also eggs, as the case may be). The serum concentrations in these people are generally found to be normal and cases of a deficiency are thus relatively rare. In the case of the pure vegetarians and vegans, cases of a deficiency are equally rare, i.e. even though their levels are sometimes below the normal level.
Why is a vitamin B12 deficiency rare in vegetarians?
The lack of a B12 deficiency amongst vegetarians is largely attributed to the following:
- Vegetable and plant-based foods can contain small amounts of B12 which are sufficient to cover requirements.
- The body's B12 reserves last longer than those of all other known vitamins. The body, and in particular the liver, keeps a reserve of around 2 - 5 mg of B12. This quantity is sufficient to cover the body's demand for a period of 3 - 5 years. B12 is largely secreted into the small intestine together with the bile juices. Most of it is then re-resorbed and restored again for future needs (enterohepatic cycle). This in effect means that, with a low or even no intake of B12, it can take up to 20 years before the reserves are depleted and clinical symptoms of a deficiency start to show.
- The bacteria in the large intestine are capable of manufacturing B12, although these are mainly the inactive B12- types (Analoga) which the body cannot use. In addition, any genuine B12 produced here can not be utilised due to the lack of intrinsic factor needed to aid resorption. On the other hand, the greater quantities of fiber consumed by vegetarians tend to promote the settlement of bacteria in the lower areas of the small intestine and hence also the production of B12 in this region. As there is normally also a sufficient concentration of intrinsic factor in this area, the body is able to utilise any B12 that the bacteria may produce here.
- The bacterial flora in the mouth and throat can also contribute towards covering the demand.
- Another area of discussion is the apparent lack of any B12 deficiencies in countries with a less stricter sense of hygiene. Microorganisms, insect pests and sometimes faecal remains (from the use of animal manures) can all be found on food plants. If such plants are not thoroughly washed, such microorganisms can be consumed and also contribute towards providing B12. There are recorded cases of Asians who emigrated to western countries suffering from a B12 deficiency even though they never changed their diets. Such cases have been attributed to the generally higher standard of food hygiene in the modern western countries.
One problem which should not be underestimated is when babies are exclusively breast-fed by mothers who have practised vegetarianism for a protracted length of time. There have been reports of children with serious neurological and haemotological disorders due to the mothers not having sufficient B12 in their milk. Studies have shown that the vitamin B12 level in the blood serum of a mother roughly equals the concentration found in her milk, and that the level in the milk tends to slowly decline on a strict vegetarian diet. It is thus important that pregnant vegetarian women wishing to breast-feed their child have the level of B12 in their blood monitored during prenatal checkups. The vitamin B12 concentration in the serum of the child should also be established (also after having weaned off) as the liver reserves of small children can be very low or even non- existent.
Vitamin B12 preparations should only be taken if prescribed by a medical doctor, and preference should be given to those preparations which contain B12 as the only active ingredient. Vitamin B12 in multivitamin and mineral preparations is hardly resorbed at all. In addition, such preparations often contain mainly the inactive types of B12 (Analoga), which can also result through interaction with some of the other constituent substances.
-----
so far prof. leitzmann.
in our microbiologic lab we do the quality control for the largest producer of vitamins in germany since 1996. so we had to learn the analytics and the behinds the hard way and read a lot of literature, until we knew, that MOST of the vitamin b12 in food are useless analogons. this also means: most of the analyses on vitamin b done in food before 1990 are more wrong than right. the published old values are at least twice as high as in reality (it doesn't matter very much in practise, because the recommandations based on these data are ALSO at least twice as high as ASSUMED neccessary today - there's no KNOWN minimum for humans, additionally animal tests are done with the pure b-12, quite unrealistic). just reading the abstracts is almost useless, because you definitely have to know the METHOD, the data were derived by. and these were rarely mentioned in the abstracts.
questions: have you ever wondered where some of the strongest strictly plant-eating animals in the world get their B12 from? (non-ruminants like gorillas or horses etc. ruminants get their b-12 from the bacteria digested in the rumen. btw: are elephants ruminants ?? my guess: no. their diet consists of less than 1% "meat" like bugs as undesired contamination taken up with plants)
the half life cycle of b-12 is about 1400 days, which means, if i don't get ANY b12 by nutritition and intrinsic factor (a glycoproteid), i will still have 50% of my pool after a bit more than 4 years of not having ANY b12. it will be depleted after >20 years..
The critics PRO vitamin b12 are thus right in some respects, but also fail to explain how the bacteria manage to survive on the COOKED meat they eat. cobalamin is mostly destroyed by cooking !! you may guess yourself, how much RAW meat mr. average eats throughout a whole year. i largely doubt, that esp. americans even get a chance to eat RAW meat anywhere at all.
from medline:
TI: Vegetarian diets and children. AU: Sanders-TA; Reddy-S AD: Department of Nutrition and Dietetics, Kings College, University of London, England. SO: Am-J-Clin-Nutr. 1994 May; 59(5 Suppl): 1176S-1181S AB: The diets and growth of children reared on vegetarian diets are reviewed. Excessive bulk combined with low energy density can be a problem for children aged < or = 5 y and can lead to imparied growth. Diets that have a high content of phytate and other modifiers of mineral absorption are associated with an increased prevalence of rickets and iron-deficiency anemia. Vitamin B-12 deficiency is a real hazard in unsupplemented or unfortified vegan and vegetarian diets. It is suggested that vegans and vegetarians should use oils with a low ratio of linoleic to linolenic acid in view of the recently recognized role of docosahexaenoic acid in visual functioning. If known pitfalls are avoided, the growth and development of children reared on both vegan and vegetarian diets appears normal.
"Staging vitamin B-12 (cobalamin) status in vegetarians", _American_Journal_of_Clinical_Nutrition_, volume 59 (supplement), pages 1213S-1222S:
"About one-third of the 'vitamin B-12' in serum is in fact not cobalamins (which are all forms of vitamin B-12 that are active for humans), but other corrinoids that are metabolically dead for humans but active for bacteria. Thus, many microbiologic assays may find normal 'vitamin B-12' concentrations in vitamin B-12-deficient people because the assay is reading as vitamin B-12 what is in fact noncobalamin corrinoids."
"Vitamin B-12: plant sources, requirements, and assay", _American_Journal_of_Clinical_Nutrition_, volume 48, pages 852-858:
"Vitamin B-12 is of singular interest in any discussion of vegetarian diets because this vitamin is not found in plant foods as are other vitamins. Confusion about what sources may yield vitamin B-12 to strict vegetarians has arisen because the standard US Pharmacopeia (USP) assay for vitamin B-12 does not assay only vitamin B-12. In the USP method the content of vitamin B-12 of any given food is determined by making a water extract of that food and feeding the extract to a bacterium (_Lactobacillus_ _leichmannii_). The quantity of vitamin B-12 is determined by the amount of bacterial growth. The problem is that what is active vitamin B-12 for bacteria is not necessarily active vitamin B-12 for humans. Many of the papers in the literature give values of vitamin B-12 in food that are false because as much as 80% of the activity by this method is due to inactive analogues of vitamin B-12."
---
adults do tolerate a lot of deficiencies, children don't!!. the first thing pediatricians are taught at university, is that children are NOT to be treated like SMALL adults, but VERY different (they are much more robust against pocks, but less robust f.e against a lack of vitamin b12.)
summary: b-12 recommandations and contents in food found in older literature are questionable, these in newer articles are contradictive. the same with the constant claim, that vegans do lack sufficient vitamin b (the whole group). seventh-day-adventists and mormones both live longer and healthier than the rest of you. both of them rarely smoke, both don't drink alcohol, but while the adventists don't eat meat, the mormones do so (see the framingham study). so health seems less to be a question, whether you eat meat or not, but whether you live an elsewhere healthy life.
everythink in moderation (see next mail ;-]) is also valid for meat! None of the big world religions forbids eating meat. the fact, that mohammed forbad pig's meat, might well be attributed to his egoism: his family members were known donkey breeders for at least 4 generations ;-) (more realistic, that it was wellknown, that pig meat spoils very fast under the climate, where moslims live and often has intestine worms).
there's another interesting finding: about 15 years ago most of the finnish population had a real lack of b-12. reason: their food mainly consisted of raw dried fish and in parallel it was found, that 70% of the fins suffered from tapeworms. it were the tapeworms, who consumed most of the b-12 in the gut. the finns were treated against the tapeworms, the b-12 deficiency "mystically" disappeared...
stomach cancer (where the whole stomach is surgically removed), is one of the rare other reasons, one NEEDS additional b-12 injections. except for weaning mothers and the mentioned reasons i know of no other reason, you need to care about b-12 supplementation.
Herbert V: Vitamin B12: Plant sources, requirements, and assay. Am J Clin Nutr 48: 852-858, 1988.
Albert MJ, Mathan VI, Baker SJ: Vitamin B12 synthesis by human small intestinal bacteria. Nature 283: 781-782, 1980.
Herbert VD and Colman N: Folic acid and vitamin B12. In Shils ME and Young VR (eds): Modern Nutrition in Health and Disease, 7th ed. Philadelphia: Lea and Febiger, 1988; 388-416.
Immerman AM: Vitamin B12 status on a vegetarian diet. A critical review. Wld Rev Nutr Diet 37: 38-54, 1981.
Specker BL, Miller D, Norman EJ et al: Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptambel dietary source of vitamin B12. AM J Clin Nutr 47: 89-92, 1987.
Kondo H, Binder MJ, Kohhouse JF et al: Presence and formation of cobalamin analogues in multivitamin-mineral pills. J Clin Invest 70: 889-898, 1982.
even the beri-beri and the lack of vitamin b-1 is a scientific hoax and the unability of today's science to draw new conclusions is a real shame !!! not even prof. eijman, who got the nobel-price for his work on b-12, did not believe in beri-beri due to b-1 deficiency. the story is a classic, but it is WRONG. just do a search on "eikjman", his scholar prof. "oomen", "thiamin" and esp. "citreoviridin" (a mycotoxin found in spoiled rice). not only was this the only case, where a nobel winner did not believe in the declared REASON for gaining the price, he even refused to go to stockholm to receive the price, but instead sent his scholar to appease the committee... the relation between beri- beri and b-1/thiamin was "distilled" much later from his research. he himself never believed it.. today it's known, that he was right. the only real beri-beri is the "dry beri-beri" from hard-core alcoholics.
what strict vegetarians are really lacking, is vitamin D, as most practical doctors can tell you. rachitis is a much more TYPICAL symptom of vegetarians (and again esp. in children) than vitamin b12 deficiency, even for those, who get lots of sun.
klaus
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