Talk:Vitamin B12

Moved from Talk:Cobalamin:
In accordance with Wikipedia:WikiProject_Drugs naming policy, I propose we move this page to the INN cyanocobalamin. If you have any concern with this proposal, please discuss it on this page. Matt 00:06, 22 Dec 2004 (UTC)

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The page should be renamed to B-12

The present name "cyanocobalamin" is misleading, as this substance is not equivalent with vitamin B12 and does not occur in nature. It is not well assimilated by the body. Moreover it is transformed to harmful cyanides when metabolized.

Cyanocobalamin has been the most used drug for supplementing B12, but this is only because it has been the most profitable substance to produce. By using the name Cyanocobalamin for B12 commercial interests are supported at the expense of public health, because Cyanocobalamin is not a good supplement for reasons as follows.

There exists increasing evidence indicating that the use of cyanocobalamine for neurological disorders including Alzheimers diseas is inadequate, because it is not well taken upp by the nervous system. Some researchers have even suggested that a factor in at least in some cases of Alzheimers, is a weak uptake of B12 into the brain circulation. Tragically, some studies using cyanocobalamin for Alzheimer have concluded that B12 is not very effective treatment for Alzheimer, while in reality the reason may have been that the preparation was not taken up by the brain. On the other hand, studies using methylcobalamin for Alzheimer have reported good results. Methylcobalamin is the natural form that is especially useful for the brain.

Actually, the medical use of cyanocobalamin has been questioned by some scientists. S.I. Terry pointed out in the Lancet that an incalculable number of people with neurological disorders due to B12-deficency are put at risk because of the inability of cyanocobalamin to correct the B12 deficiency in the nervous system. (Terry, S.I. et al. "Survival of Cyanocobalmin." The Lancet, October 14, 1978, pg. 848.)

Dr Linnel pointed out that cyanocobalamin has no known biochemical function and needs to be transformed in the body to physiologic cobalamins before it can be used. He concluded that there is no place for the therapeutic usage of cyanocobalamin (Linnell, J.C. et al. "Therapeutic Misuse of Cyanocobalamin". Lancet, November 11, 1978; pg 1053-1054.)

As deficiency in the nervous system is an especially serious complication of vitamin B12 deficiency, a name should not be used that makes people wrongly believe that cyanocobalamin is equivalent with vitamin B12 and therefore an adequate treatment for such serious disorders.

Methylcobalamin is actually the predominant form of B12 in the body as 90% of the active form of B12 in the blood is this molecule. But in the liver, kidney, brain and erythrocyters, adenosylcobalamin (also called dibencozide) is predominant.

So as there are different forms of B12 in the body, it would be sensible and most adequate to use the simple common denominator "vitamin B12".

Finally, the motivation for renaming from B12 to cyanocobalamin was that this was in accordance with Wikipedia:WikiProject_Drugs naming policy. However, B12 is not a drug (but cyanocobalamin is), it is a common denominator for a group of physiological molecules of vital importance for the normal functioning of the body.

CONCLUSION: There are strong reasons why the cyanocobalamin page should be renamed back to its original name "B12".

--Võitkutõde 06:10, 19 June 2007 (UTC) M.D.

I second this. I think that this page should either be about B12 in general or cyanocobalamin specifically. Cyanocobalamin is the most ineffective form of B12 so it should not be equated with the vitamin.24.83.178.11 07:29, 2 November 2007 (UTC)BeeCier

I agree. This page is primarily about the vitamin and not about the drug Cyanocobalamin, although of course it refers to it. As a result it is incorrect to use the wikipedia drug naming policy since this article is not about the drug. One middle option would be to have an article on the drug separately with suitable cross-referencing and translusion. The incorrect name of the article is very striking even after reading only a few paragraphs (without prejudice as to whether the drug cyanocobalamin is in fact any use or not). How did we get here? Francis Davey 00:18, 3 December 2007 (UTC)

== What other species need vitamin B-12 from outside sources (their diets)? This should be listed in this article. For example, it is a widely-known fact that human beings need vitamin C from their diets, and that guinea pigs need to eat it, too, but that most other animals produce their own vitamin C. It would be good to have at least a bare-bones level of this information here for vitamin B-12, instead of concentrating 98% on human beings. DAW

Some strange citations

Some of those external links are pretty bad. The Advice for vegans on B₁₂ article sounds like it was written by a high school student. Also the Vitamin B₁₂ information seems to be down. I'm not sure if the site is gone for good or what. I'll have to see if I can add a bit to this article. --Genericdave 22:50, 23 October 2005 (UTC)

I agree and thus removed the "Advice for vegans" link. Not only is the style of the article (transscript?) poor, it also contains grave factual errors, for instance: Vitamin B-12 is made by little microscopic plant cells called soil bacteria. The vegansociety.com does a much better job to explain the issues and seems sufficient anyway. Aragorn2 11:37, 5 April 2006 (UTC)

i have no i dea wut they r talking about..u? - [User:69.237.97.141|69.237.97.141]] 23:51, 7 May 2006 (UTC)

Which bacteria?

Which bacteria produces B12? Anybody know the species?

Looking around, I haven't found any specific species mentioned but many places saying that "many" bacteria produce it. I think that it's a fairly common process for bacteria if there's enough cobalt around. However, the bacteria living in the intestine that produce it are too far down for enough to be absorbed by the host animal, so you have to get it the second time around (so to speak). See [1] for information about B12 and horses. Matt 00:49, 2 Jun 2005 (UTC)

no copyrighted materials

Please, don't submit compyrighted material. There was just now a lot of material added to the article, and some of it (in the Structure section) was taken more or less verbatim from ISBN 0471496405. I removed the whole edit because at least a part of it was copyrighted. --Andkaha^(talk) 23:49, 16 October 2005 (UTC)

Dude, what the . . . ? All the information I have used comes from several free on-line resources (magazines) and namely the introduction part of several articles. What do you mean "part of it was copyrighted" what part of it? The whole work wasn't just a simple "copy-paste", why do you ignore the fact that I have spent some time doing that. I used parts from several different sources, I had to delete a lot of junk info written by the original authors , such as history references, then I had to organize the parts so the result looks compact and without any un necessary information or redundancy, and is easy to understand, and all this process takes time not some 5 min or even half an hour but much more than that. If you think some parts of it were somehow "copyrighted" why did you take out everything incluiding the info for the enzymes, which can be found in any Biochemistry textbook, and finaly why did you take the pictures out? Are they copyrighted too? I made the pictures using ISIS Draw, then i converted the files into *.bpm and eventually *.png. I am pretty sure those who have studied B12 would be happy to share their knowledge with the world for FREE. And then i have never seen before the book you have given a reference to - ISBN 0471496405. BorisTM 13:17, 31 October 2005 (UTC)

Good day to you too. I'm sorry I upset you (or so it seems anyway). I based my fact on a simple google search on some of the phrases used in the Structure section of your edit. They all pointed to here. The book text might be available for free, but it is copyrighted. I reverted the edit because of this and also because I simply couldn't tell the source of the rest of the material. If you feel strongly about including this text in the article, then please cite the sources. See e.g. WP:V and WP:CITE, and also Wikipedia:Copyrights#Using_copyrighted_work_from_others. Kind regards, Andkaha^(talk) 16:24, 17 October 2005 (UTC)

Alright. BorisTM 13:17, 31 October 2005 (UTC)

Someone should take a look at this and relate it with the b12 article:

http://www.rawbc.org/articles/B12.html

It could be explored the nutritional side of it and the vegetarian, etc., diets and relation to B-12

Why is there no information about miso - a paste that is well known to contain B12 and fits the vegan dietry? And if B12 is present only is non-vegan food, how comes that meat eaters also have a lack of B12? Some statements simply seem to be either contradicting each other, or to be based on still not enough researched ground. 84.145.231.254 02:43, 15 January 2006 (UTC) renu

Huh? Isn't the article clear that meat & milk consumers can get Vitamin B-12 deficiencies when the processes for absorbing B-12 in their digestive systems don't work correctly? In other words, food/liquids containing vitamin B-12 is consumed, but it "goes straight through" without being absorbed.

The same problem occurs in some people when they have diseases that cause them not to absorb important vitamins, minerals (incl. iron), amino acids, etc. These diseases can make the victim suffer sicknesses, go blind, and even die.

An interesting question is, how comes that cows have a lot of B-12? Do they eat other cows, or all their life drink cow-milk?? I don't know about such ones, I must admit. Ra

Their gut microflora, the very same one that enables them to digest the plant material, provides them with enough B₁₂. -- Boris 18:02, 29 January 2006 (UTC)

As the article states, bovines, horses, etc., do eat grass, etc., that has had solid wastes excreted onto it by the animals themselves, or by other species.

heard that E.coli do produce it (by rumor of course)

From page

This was posted as a HTML comment in the article. I thought it would get more attention here.

Later on in this article, nori and barley grass are given as (inadequate) sources of B12, and another plant - Angelica Sinensis - as being a good source of B12. This contradicts the statement that B12 cannot be made by plants - so there is a problem here (from User:195.10.41.13)

Matt 00:12, 24 February 2006 (UTC)

I think the part refering to the Steven Segal drink should be striken. Remember 18:45, 1 March 2006 (UTC)

mcg?

Why is this article using mcg instead of µg? Should it be changed? 218.103.142.233 03:35, 19 March 2006 (UTC)

I would be inclined to agree. --Gak 20:57, 6 November 2006 (UTC)

Yes, use the modern symbol for microgram μg - or it is not really too much trouble to type "microgram". Other modern units for mass include the nanogram (ng) (rather than the milli-microgram) and the picogram (pg) (rather than the micro-microgram.

Angelica sinensis

Quote: The only known vegan sources of substantial B12 ... are the Chinese herb Dang Gui (Angelica sinensis), used for centuries for treating anemia

Every so often, a new claim about vegetable sources of vitamin B12 pops up. The problem is that some plants do contain molecules structurally related to the known variants which might be new forms of vitamin B12 (AFAIK the only substances known to be fully active vitamin B12 are cyanocobalamin and methylcobalamin), but they are not known to provide full vitamin B12 activity in humans, or even known not to provide it. For example, the substances contained in "Dang Gui" may show vitamin B12-like activity when it comes to blood formation, but might lack vital vitamin B12 activity in one or several other areas (e.g. removal of homocysteine, myelin formation etc.). The article should make it clear that this source of (what might be) vitamin B12 cannot be considered safe until at least one of the following have been demonstrated:

• Angelica sinensis contains cyanocobalamin or methylcobalamin.
• Angelica sinensis contains a chemically related substance that exhibits full vitamin B12 activity in humans. Aragorn2 11:52, 5 April 2006 (UTC)

Granny Smith apples

Research by Krug, et al. at the U of Munich (Journal von nutrional Medizin Januar 2004 v.17 ausgabe #1, seiten 169-178) showed that Granny Smith apples contain an adequate amount of b-12. They concluded that eating 3 medium sized apples per week provides a "minimum functioning requirement." It was interesting to note that the other apples that Krug tested were "significantly lower than granny smith." They theorize that the granny smith is the least hybridized of these apples and that might account for its high nutritional content. ---Guthrie March 12 2006

Where does the chicken get it?

Where does the chicken get it's B₁₂, to put it into the egg?

Oh, yes and where do the animals take their B₁₂ to put it in their meat? It sounds a bit inconsistent to me. -- anonymouse

Animals don't make B12 either, they get it by eating dirt which contains the bacteria which makes it. It's more abundant in natural, healthy soils. B12 for supliments and fortification is cultured from those same bacteria - grown in large vats.

This argument is very weak, plants get all they need from soil, sunlight, and water, planting a person would be pretty ineffective even though they would have all the elements that a plant requires to grow. The fact is that human beings cannot synthesize B₁₂, period. I assume the chicken gets the B₁₂ where we do, microscopic organisms. These are found naturaly in our guts, and in the soild. Unfortunately in our guts they are too far down the digestive tract for proper B12 absorbsion. I am not sure if any animals are capable of B12 synthesis. (P.S. I am vegaterian so I worry about B₁₂ --Mig77 09:52, 18 May 2006 (UTC)

Please read section two (2) of this link EZNC. That should explain where cows, and possibly other animals get their B12 from. Thanks. C3045051 05:03, 19 August 2006 (UTC)

>>Hi In the "sources" part I took out the bit about bacterial contamination. I think this is very confusing; it sounds like the meat itself is covered with bacteria containing B12! The best source of B12 is from animal products, and as for where the animals get it from....this should go somewhere else, maybe under synthesis, or create a new paragraph. I also think the paragraph "B12 deficiency is very common" should go under the deficiency paragraph. Juliakbird 19:07, 6 August 2007 (UTC)

Plant Cobalamin

Coca leaf contains B12. So does American Ginseng. Look for "Vit-B12" in the Ginseng and Coca listings on "Dr. Duke's Phytochemical and Ethnobotanical Databases. [Online Database] 31 October 2006."

Cobalamin and cyanocobalamin are NOT the same thing. The article should be called "Cobalamin" with "cyanocobalamin" as a subheading, under which it actually states what cyanocobalamin is. The "purification process" involves poisoning vats of fermenting bacteria with cyanide so that they will secrete cyanocobalamin (cobalamin bound to cyanide). (See the Wikipedia article on Cyanide under the heading Treatment of poisoning and antidotes.) Cobalamin is the human body's natural defense against cyanide poisoning.

Depending on cyanocobalamin supplements for your B12 means that your body is unable to protect itself against cyanide, and if you get no other source of B12, you are likely to be diagnosed with bi-polar disorder ("At doses insufficient to cause loss of consciousness, the symptoms can also include faintness, drowsiness, anxiety and excitement." Wikipedia article on Cyanide, under Subacute poisoning).

--4.245.95.7 04:25, 4 July 2006 (UTC)Dyjak

That's an interesting argument. Can you please provide some links to references so that people can expand this article? Thankyou. C3045051 05:06, 19 August 2006 (UTC)

I would agree with the part that says cobalamin is vitamin B12. Cyanocobalamin, hydroxocobalamin, methylcobalamin, etc. are all variations on a theme, because cobalamin cannot exist independently (the empty site must be filled). The article title should be cobalamin and not cyanocobalamin, which is merely one form of the compound. --Gak 21:01, 6 November 2006 (UTC)

I agree. Equating B12 with its cyano complex is misleading. 67.117.145.193 08:15, 17 December 2006 (UTC)

Use of Drugbox vs Chembox templates

Vitamin B12

Clinical data
Routes of administration	oral, iv
ATC code	B03BB01 (WHO)
Legal status
Legal status	UK: POM (Prescription only)
Pharmacokinetic data
Bioavailability	readily absorbed in lower half of ileum
Protein binding	Very high to specific transcobalamins plasma proteins binding of hydroxocobalamin is slightly higher than cyanocobalamin.
Metabolism	hepatic
Elimination half-life	Approximately 6 days (400 days in the liver)
Identifiers
CAS Number	68-19-9
PubChem CID	5479203
DrugBank	APRD00326
Chemical and physical data
Formula	C63H88CoN14O14P
Molar mass	1355.37 g/mol g·mol−1

Given, as the article states that "cyanocobalamin, which is the principal B12 form used for foods and in nutritional supplements" and the article mostly discusses deficiency conditions, "Side effects, contraindications, and warnings" and "Interactions with drugs", would the template:drugbox be a more useful source of information? It also allows 2 sets of images which the current article awkwardly shows. I provide here what I propose with the template partly/largely already filled-in. However, I recognise that B12 is a natural compound and relates therefore not exclusively to medical discussion, so I can foresee others disagreeing - hence my hesitation at being BOLD. So please let me know what you think :-) David Ruben ^Talk 23:59, 6 September 2006 (UTC)

I like it. Put it in! B12 is excreted in the urine as are all B vitamins (being water soluble). B12 excretion in the urine is also the basis of the Schilling test.--Gak 16:01, 11 September 2006 (UTC)

Termites

Termites contain B12 because B12 is contained in all animal food sources. How is this relevant or interesting? I move to delete this.--Gak 15:59, 11 September 2006 (UTC)

I disagree. The section is Sources of B12. Following this line of thought one should delete the references to eggs, dairy etc. too. Just leave a reference that says B12 is contained in all animal food sources (I bet you will have trouble finding a reference for that blanket statement). As to the relevance: Do insects contain B12? yes. Has it been scientificaly measured? yes. It this quantity of B12 significant? (see reference). Granted you may nof find this interesting (so rephrase), but it is relevant, because they contain B12 and this is a section on Sources of B12. --Mig77^(t) 10:42, 12 September 2006 (UTC)

allergy

Is it really necessary to have the annoying and irrelevant comment on allergies. There is about one case report of B12 allergy per decade in the medical literature; and it is obvious that people who are allergic to it should not take it. Of course this doesn't stop fish from a supermarket having a sticker which says, "may contain fish," but we do not have to play their silly games. In any case, it is suggested in those rare case reports that it is IV preservative, or something other additive which has caused the allergy. It is too rare for anyone to have bothered to find out what. —The preceding unsigned comment was added by Waster (talk • contribs) 17:47, 22 March 2007 (UTC).

Dear Editors:

I believe the ATC code for cyanocobalamin is listed wrong in Wilkipedia. The web page has: B03BB01, but the ATC code should be B03BA01.

Sincerely yours, D. d.papsun@prosoftsoftware.com

Simple Explanation?

OK, I can see there's plenty of chemistry on these vitamin articles but can anyone make a nice clear explanation of exactly what vitamin B-12 is used for in the body and what benefits it has? I mean explained in simple terms, I've read this article three times and still don't know exactly how taking vitamin B-12 will benefit anyone. —The preceding unsigned comment was added by 82.7.60.108 (talk) 18:39, 27 April 2007 (UTC).

The two main uses of vitamin B-12 by human beings are these:

A. It is needed to manufacture the parts of the blood that contain iron. You get anemia without adequate vitamin B-12

B. It is needed for various purposes for your nervous system to work right.

Vitamin B-12 also performs other functions in many places, but in many of those, folic acid will do just as well.

Hydroxycobalamin should be a separate entry

Since the title of this page is specific to Cyanocobalamin, Hydroxycobalamin (vit B12a) should be under a separate listing. I believe it has its own history, research, chemical structure, etc...
Szalzala 15:16, 7 May 2007 (UTC)

Vitamin B12 in vegans.

Vegetarian diet does not have Vitamin B12, as it is exclusive to animal sources(as far as dietary intake is concerned.) Vitamin B12 is absorbed in the terminal ileum, which is (obviously) proximal to colon. The ileo-caecal valve, physiologically, prevents any reguritation of tubal-contents from caecum back into ileum. Vitamin B12 defeciency is a rare condition in vegans (I've known hundreds of vegans who have never taken vitamin supplements and yet have never had Vit B12 defeciency) because it has been documented that colonic bacteria do the favor of providing a vegetarian with Vit B12 by producing it. Then how does a 'thing' produced later in the gut be absorbed proximal to it?

59.180.44.61 11:21, 11 June 2007 (UTC)Steve

True single direction of flow. Two thoughts:

1. Is "colonic" used here in the more general sense of "bowel", which would include both the large (colion) and small intestines ? If so then the intestinal bacteria would be making B12 before the terminal ileum.
2. The terminal ileum absorbs a lot of things, but not generally exclusively so compared to anywhere else in the intestines. Hence other areas will also absorb nutrients, but just not as efficiently as the terminal ileum. (likewise alcohol aborption can be significant through the mucus membranes in the mouth - hence why shots of vodka are gulped down in one go rather than slowly sipping away, yet the mouth is clearly not the main area for the majority of alcohol absorption). David Ruben ^Talk 13:53, 11 June 2007 (UTC)

Gut bacteria do produce B12, but it has never been documented that colonic bacteria can compensate for a person's lack of intake of B12, if it does, its probably extremely minute. It can be very dangerous to tell individuals that the bacteria can. Although its true that some people who dont eat animal products do not exhibit B12 deficiency, its important to also know that B12 deficiency takes years to occur. Its very possible that some people just havent been vegans long enough to feel the effects. In addition, humans have some capacity to adjust to a lower B12 reserve. Depending on your B12 reserve it could be between 4-6 years before you begin to notice anything. And if you actually do start noticing anything, your first thought probably isnt going to be B12 defiency, because the associated symptoms are not immediately specific. Its also been observed that any increased folic acid diet (such as most diets in the United States, due to fortified foods) can mask the symptoms of B12 deficiency. This is especially true when you look at their effects on the blood, in particular megaloblastic anemia.

On another note, animals use different mechnisms from humans to obtain Vitamin b12. Bovine and other herbivores actually do rely on their gut bacteria for B12. This is because their gut is structured different than ours and allows B12 producing bacteria to be present in much more locations. The act of regurgitating their food and repeatedly chewing it is one factor that contributes to the release of B12.

Chickens get their B12 from ingesting their own droppings.

Symptoms are missing from article

Someone needs to include a symptoms section. Readers coming to this page to check if they have the deficiency have no way to compare their symptoms to the standard symptoms. Skopp (Talk) 22:43, 15 June 2007 (UTC)

Symptoms included

I made a major update of the page including, symptoms diagnosis and causes of deficiency. I will add more references to these sections when time allows.

--Võitkutõde 06:55, 19 June 2007 (UTC) Physician

B12

I couldn't find any info on what the recommended daily allowance is for the average adult. It would be helpful if someone would provide that information. Dcot 03:21, 25 June 2007 (UTC)
--- REPLY: Because of the clearly wrong normal values, the daily allowance values are also most probably wrong as it takes significantly more B12 to uphold more than twice as high a blood level as formerly believed to be sufficient. Therefore there are no acceptable RDA values presently. But it is very clear that B12 is non-toxic and people have been treated with doses over ten thousand times higher than the present RDA without any other effect than becoming cured from their neurological disorder. --Võitkutõde 13:29, 7 July 2007 (UTC)

Symptoms and damage from deficiency

I question that Alzhiemers dementia is the *most* serious consequence of B-12 deficiency. Secondly, I am curious as to where the claim that 'most physicians are unaware' of this came from. I suspect 'most physicians' would be 'most offended'. I shall remove it. Drowner1979 13:19, 26 June 2007 (UTC)

____

REPLY: I cannot think of any more serious consequence of B12 because of the devastating effects of this disorder.

I am a physician and have been working in the US, Sweden and Germany. I am a specialist in internal medicine and have dealt with B12 cases since over 30 years. It is my experience from all these countreis that very few cases of Alzheimer have been treated effectively with B12 because of a general unawareness of this connection until lately. And even presently, because of the wrong reference values, many cases of Alzheimer with "normal" blood values according to the outdated standards, have been untreated. This is highly tragic as a connection was strongly indciated already over 20 years ago and hundreds of thousands of people all over the world would have been saved from this serious disease if the scientific findings had been applied. --Võitkutõde 13:20, 7 July 2007 (UTC)

I think what's highly tragic is your complete misunderstanding of the pathophysiology of vitamin B-12 deficiency. I fail to see how anyone practicing medicine for thirty years could equate B-12 deficiency with Alzheimer's disease. You have no scientific basis for this association, other than your personal experience, if that. You should review the policies of Wikipedia: it is not a venue for publishing original research. I think we should stick to the scientific method as a way of knowing, and part of the scientific method is that experiments should be externally verifiable. If you cite your own experience as the sole support of your claims, that makes your claims unverifiable by definition, and therefore suspect as false.--Dr.michael.benjamin 04:40, 8 July 2007 (UTC)

I agree that the scientific method MUST be used, and that the Wikipedia is no place for speculative notions at all. Also, even it it was verified that vitamin B-12 deficiency had something to do with Alzheimer's Disease, it wouldn't be the "most serious consequence". Pernacious Anemia in children & young adults is a far more serious consequence that Alzheimer's among the elderly. Sorry, but serious diseases among young people are just more important than diseases of old people who don't have many years to live anyway. It is a matter of the lost years and longer suffering.

'Contradictory' Tag

I added this tag to the 'causes of deficiency' because the statistics don't seem to match up.

 A large study in the US found that 39 percent had low values

Now, compare the above to the two following statements:

 Absorption decreases with age so older people are under significant risk to be deficient. In one study 40% of people above 65 were deficient in vitamin B12
 Recent research has found that B12 deficiency is common among vegetarians - as much as 30% may be deficient

If prevelency among the general population is 39%, a 1% greater prevelency among the elderly hardly seems noteworthy. Moreover, according to the above, vegetarians are 9% LESS likely to suffer a deficiency! --Xiaphias 15:54, 28 June 2007 (UTC)

---

REPLY There is no contradiction. I am referring to different studies using different methods of selection, and therefore the numbers may be different. This is common in medical materials. The vegetarians had deficiency, but the 39% of the general population had low levels or deficiency. However, considering that there are strong reasons to believe that the normal levels are too low, actually a much greater proportion in each category probably had deficiency. --Võitkutõde 13:03, 7 July 2007 (UTC)

I don't see any citations of this data, and I added annotations until we can come up with citations. Orthomolecular journal citations would have to be reviewed before deemed appropriate for inclusion here--my library don't subscribe to those journals. We should demand a large preponderance of evidence before turning away from established benchmarks of diagnosis.--Dr.michael.benjamin 23:17, 7 July 2007 (UTC)

There is a large question of definition here. MOST vegetarians are not vegans, and MOST vegetarians consume food & drink like cheese, butter, and milk that contains vitamin B-12.

I also agree that extraordinary claims require extraordinaty evidence in any field of discovery or knowledge. —Preceding unsigned comment added by 72.146.44.249 (talk) 00:11, 3 March 2008 (UTC)

Symptoms and damage from deficiency

Please, could whoever wrote that stuff about the 'inaccurate' reference ranges back it up with a quality reference? The site given appears to be an advertisement. The claims made appear to be unjustified. This is not a forum to claim a new and controversial theory as fact. If you wish to mention that one author seems to consider that the reference ranges are incorrect, thats fine, but surely stating that point as fact in bold text reeks of spam.

---

REPLY

The present reference values are from the olden times when most research was made on B12-deficiency anemia. Several studies in later years found that neurological disorders could appear without anemia. This resulted in research indicating that much B12 higher levels are needed to prevent neurological damage.

Japan has not changed its reference values on the basis of extensive research. Here are a few references concluding that the lower reference levels should be increased to more than double that of present values:

VanTiggelen CJM, Peperkamp JPC, TerToolen JFW. Vitamin-B12 levels of cerebrospinal fluid in patients with organic mental disorder. Journal of Orthomolecular Psychiatry 12: 305-11, 1983. [Concluded the minimum value should be 600 pg/ml]

Mitsuyama Y, Kogoh H. Serum and cerebrospinal fluid vitamin B12 levels in demented patients with CH3-B12 treatment - preliminary study. Japanese Journal of Psychiatry and Neurology 42, 1: 65-71, 1988. [Concluded the minimum value should be 550 pg/ml] --Võitkutõde 13:03, 7 July 2007 (UTC)

The above is garbage, I say. Your summaries and citations are not persuasive enough to warrant changing the standard thresholds. If you can explain why the B12 deficiency threshold should be changed in terms of the Receiver operating characteristic, then maybe I'll go along with your scheme to foist a new standard on us through Wikipedia. If you don't know what that is, or can't muster the data to support your claims, please desist in making POV edits to the article.--Dr.michael.benjamin 07:02, 10 July 2007 (UTC)

Vitamin B12 is a popular substance for use in diluting (or cutting) methamphetamine.

Vitamin B₁₂ costs about €70 per gram, substantially more than methamphetamine! It is also bright red in colour. Removed as vandalism. Physchim62 19:29, 29 May 2005 (UTC)

Absorption Paths

Sentence in article section Human digestion needs clarification / modification. It says:

Absorption of vitamin B12 therefore requires an intact and functioning stomach,
exocrine pancreas, intrinsic factor, and small bowel.

Article on intrinsic factor notes:

From  More recently, Swedish researchers discovered that sufficiently large doses
of B-12 can also be absorbed sublingually, so injections are necessary
only for those unable to take pills by sublingual administration.

The sentence may be correct for the absorption path for vitamin B12 from normal food sources. Perhaps it would be sufficient to say "Absorption of vitamin B12 therefore normally requires..." Samatva 02:07, 15 July 2007 (UTC)

There is nothing special about the sublingual route (no proof that B12 is absorbed better that way). But the fact that massive doses (500 mcg and up) by mouth every day can treat even lack of intrinsic factor, by mass action, has been known for 30 years. This needs to be added, and I'll do so when I find the references.

Also, I don't much like the title of this article. It should be "Vitamin B12" with "B12" and "cyanocobalamin" (and other vitamers) redirecting to vitamin B12. Cyanocobalamin is an unnatural molecule which arises when bacterial B12 from cultures are filtered through activated charcoal; the natural vitamers react with the cyanide in the charcoal, for which they have high affinity, and cyanocobalamin results. This molecule is very stable and easy to crystalize, which is why it's commercially produced and is the most common form the vitamin, particularly in multivitamins. But the body has a bit of difficulty getting the -CN off, particularly in "tobacco amblyopia" where there's cyanide to be dealt with all the time. So I hate to see "cyanocobalamin" put up as "THE" name for the vitamin. It's not! The vitamin, like all vitamins, is not the name of a particular chemical entity so much as the entire class of entities which have the necessary vitamin activity which defines the vitamin. Niacin and niainamide are both vitamin B3, for example. And so also with this vitamin. SBHarris 00:19, 24 October 2007 (UTC)

Following the dictum to BE BOLD

I have fixed up this whole mess, so that vitamin B12, which is a class of compounds, not "cyanocobalamin", now properly directs to the whole class of molecules with B12 activity, not just cyanocobalamin. Cyanocobalamin, in turn, now gets its own stub as being the most well-known of the B-12 vitamer class, but not a synonym for the either the vitamin or the vitamer class.

In the future, somebody may actually want to tease out the "cyanocobalamin TALK" and put it in its own section, but meanwhile it's easlier just to move most of it here, and discuss the redirect THERE. SBHarris 06:21, 3 December 2007 (UTC)

Why is there not a standard set of vitamin boxes? They are a pretty fundamental set and many other families have boxes. Francis Davey 18:46, 3 December 2007 (UTC)

There is a navigation box at the bottom of the article David Ruben ^Talk 20:46, 3 December 2007 (UTC)

Function Misunderstanding

There is a huge misunderstanding of the 2 enzymes and there function throughout this article. Basically, MUT doesn’t produce methionine, MTR (also known as methionine synthase) does. Then methionine is converted to s-adenosyl-methionine(SAM-e) via the enzyme Methionine Adenosyl Transferase (MAT).

Also this statement in the heading is incorrect: “When sufficient folic acid is available, all known B-12 functions normalize, save those connected with the enzyme Methylmalonyl Coenzyme A mutase (MUT), and its products (S-adenosylmethionine, SAMe) and substrates (methylmalonic acid, MMA).” It couldn’t be much more wrong; Both of the enzymes that require B12 would still be inactive. “Sufficient” folic acid would only correct folic acid requirements. —Preceding unsigned comment added by 62.249.237.91 (talk) 16:05, 12 February 2008 (UTC)

Good pick up. Yes, of course MTR makes methionine (though it needs HomoC to do it, which isn't in the diet, which is why methionine is essential). If it doesn't work, HomoC builts up. And also a lot of folate ends up as 5-methyl-THF with nowhere to go and nothing to do (that step in using 5-methyl-THF to convert homocysteine back to methionine is the ONLY connection between folate and B12). Does the article really say that MUT produces methionine? I can't find it, but will fix if I do.

Yes, it's true that both MTR and MUT need B12, so the activity of both enzymes is interrupted if B12 is deficient (that does need a fix). So the bad things that happen from B-12 deficiency are BOTH due to MUT deficiency (methylmalonic acid buildup), and ALSO MTR deficiency (homocysteine builts up). So the article should say that when folate is available, all B-12 functions relative to DNA normalize, not those relative to MTR. Since of course if you have enough folate, you need no MTR to rescue 5-M-THF, but can continue to methylate thymidine with 5,10 MTHF which you can continue to make from dietary folate-->THF via STHM. The strictly DNA-synthesizing methyl transfer reactions which cause anemia don't depend at all on B12, and folate cycling doesn't either. Just EFFICIENT folate cycling. SBHarris 02:56, 13 February 2008 (UTC)

It implies that MUT produces methionine and then SAM-e, from the statement: "Methylmalonyl Coenzyme A mutase (MUT), and its products (S-adenosylmethionine, SAMe)", which is wrong. SAM-e isn't a product from MUT, Succinyl COA is, as it says elsewhere. This statement is also wrong, therefore: "In a vitamin B12-dependent MUT reaction, methionine is subsequently converted to S-adenosyl-methionine". It is MTR that is responsible for the eventual evolution of SAM-e, not MUT.

You say that B12 isn't needed for folate cycling, just "efficient" cycling. I understand that there are other pathways, but this is a major pathway. Without it, you would soon die. —Preceding unsigned comment added by 62.249.237.91 (talk) 15:27, 13 February 2008 (UTC)

Thanks again for the input. Again, you're right about the biochem, and this needs fixing. SAMe decreases in B12 deficiency, but nobody knows why. It even happens in some methionine supplemented models, so evidentally it's not all due (simply) to low methionines due to this essential AA getting caught in a "homocysteine" trap from which it is unable to escape via MS/MTR. But anyway, you're right that low SAMe certainly has nothing to do with MUT, and SAMe synthesis per se isn't B-12 dependent, except as you might need B12 to have enough methione around if intake is poor. SAMe/AdoMet synthesis requires needs ATP, methionine, and methionine adenosyl transferase (MAT), a non-B12 dependent enzyme (so far as I can tell, though prepare to be surprised, since we don't know all these is to know about it). However, yes, this needs revision, as MAT is presently NOT one of the two recognized classes of B-12 cofactor-needing enzymes. I will fix.

I have a bit more problem with your flat statement about how important B12 recycling of folate is. Whether I "soon die" without B12 depends entirely on what I eat. Contrary to popular opinion, megaloblastic anemia in vegans is so rare as to be reportable (a few cases are reported), but even there, it's probably (and certainly in some cases [2]) due to vegans with a low folate diet (this is possible if the vegan exists on grains, flours, nuts). The typical vegan with B12 deficiency does not have anemia, but merely low B12 and perhaps some neurological problems. Vegan children with health problems don't present with megaloblastic anemia, but rather with malnutrition from protein, calories, and many minerals, and even low vitamin D if they don't get enough sun-- B12 is the least of their problems. For adults, a vegan diet with lots of greens will have several mg of folate a day, and with that intake (5 x RDI), you have no need of folate recycling to avoid all folate dependent problems, which includes all the DNA synthetic ones. Yes, your B-12 deficiency problems of other types related to high homocysteines and MMA's will continue. But the article says that, now. Whether they kill or not, and how fast, is a good question. Clinically, it can't be fast because it's rare. Pure B12 deficiency while eating a high folate diet? It's possible in theory, but in practice-- well you find me the cites (I've looked and missed them). SBHarris 05:09, 14 February 2008 (UTC)

Has Wikipedia got a discussion forum, instead of this discussion page? It would be a lot easier, and might encourage more people to give their input.

I was on about complete lose of this pathway. B12 deficient vegans don't come close to this pathway being lost completely. Even people with autoimmune pernicious anaemia, who are far worse than vegans, don't come close. The amount of folic acid you would need to supplement with to make up for this, couldn't be met by diet, practically. This is one of the reasons why B12 is classed as a vitamin.

The whole idea that folic acid is somehow a substitute for B12 flies in the face of B12 being classified as a vitamin. I think statements like this should be changed: "When sufficient folic acid is available, all known B-12 related deficiency syndromes normalize" and “Most ‘B-12 deficient symptoms’ are actually folate deficient symptoms”. Folate recycling is only one part of what B12 does. Sure, anaemia is a very obvious symptom, but B12 is integral to krebs cycle and SAM-e methylation. Chronic fatigue is related to B12 deficiency; folic acid wouldn't correct B12's involvement in that. Depression, liver disease, adrenal fatigue and joint disease are just a few of the ailments related to low SAM-e levels. SAM-e is the universal methylating agent for hundreds of biochemical reactions which folic acid wouldn't correct. Then there’s the build up of homocysteine and methylmalonic acid which causes atherosclerosis and demyelination respectively. From a symptoms list for pernicious anaemia, the actual anaemia is caused by low folate, but the others can be attributed to B12’s other functions, sometimes in concert with low folic acid levels. —Preceding unsigned comment added by 62.249.237.91 (talk) 16:13, 14 February 2008 (UTC)

<outdent> This IS the discussion forum for B12. English Wikipedia has 2 million+ articles, and the general forums are for general discussions of how the encyclopedia works, not minutiae of biochemistry. Again, I would suggest that you register under some name, to become a "nameuser" (it doesn't have to be your real name), and build up some credibility here. At present, there's no other way to do these things. "Subject experts" are not recognized on Wikipedia, a matter which professors who find their way here, find endlessly galling (I'm trying to change this, but that's a long story).

Now, as for the topic at hand: As you know, you need neither B-12 or folate to make SAMe. All you need is methionine, which you need to eat anyway, because it's essential (you can make it from homocysteine, but there's no good dietary source of that). Vegans eat less methionine (present in meats in high amount) and so may have less SAMe, but don't mistake cause and effect. Also, don't be a victim of the alternative medicine/autism/CFS crowd, who carry on about need for vitamins to make SAMe (except when they want to sell you actual SAMe). I know of one RAT paper in which B12 deficient rats had lower liver SAMe, but not lower brain SAMe. [3]. This is NOT very good evidence that B12 effects all those neuro SAMe functions you mention. Also, you say B-12 is integral to SAM-e methylation? Says who? And on what evidence?. In pigs, the levels of SAMe don't change at all in B12 deficiency. One group suggests that the neuro problems in B12 deficiency are thus partly due to elevated S-adenosyl-HOMO-cysteine, because of the unchanging SAMe levels [4]. But nobody really knows. And the fact that people are struggling to find some other mechanism than lowered SAMe for B'12's neuro effects, means something: it means what's going on, is not as obvious as you seem to think.

The article, as writen now, has qualifiers, and says that MOST of the symptoms of B12 deficiency normalize, except those narrowly connected to homocysteine and MMA buildup. I think that's a more or less consensus [corrected spelling] view. The GI effects of pernicious anemia (PA) are in part primary autoimmune (they CAUSE the PA in the first place), and also certainly partly due to DNA synthesis loss, as your gut lining turns over fast like bone marrow, and folate deficiency is like chemotherapy. In any case, you can't just write down a list of SAMe functions and theorize. You have to show B-12 supplementation raising SAMe, and that's just the beginning. Don't quote from quacks-- primary literature, please. "Chonic fatigue is related to B-12 deficiency?" Who says? Where's the evidence, let alone proof?

As for the question of what's a vitamin, it's not a clear one. Vitamins K and D are vitamins, and you really often don't need to eat either one. Depends on circumstances. I'll look around to see if I can find a measure of how much folate is needed to restore DNA synthesis in absense of B-12. But in the meanwhile, recognize that it's an open question. SBHarris 23:34, 14 February 2008 (UTC)