B12 overdose / megadose?

[Korn]

If you have read a little about vegan food and nutrition, you know that vegans often have lower B12 levels than others. It's important to make sure your B12 levels don't get too low. Too little B12 is definitely not a good thing.

Normally, it is considered safe to take a lot of B12, but this is being discussed, and several seriously bad health conditions are associated with high B12 levels.

Here are some examples of what others have written about taking too much B12:

"What is the risk of overdose? Patients of Dr. H.L Newbold in New York City injected themselves three times daily with triple-strength doses of B12 (9,000 ug per day) indefinitely. Their serum B12 levels reached 200,000 pg/ml and more, but none had any significant side effects. Dr. Dommisse prefers hydroxycobalamin to cyanocobalamin. A person taking the latter might over a period of years accumulate a toxic amount of cyanide and possibly damage vision. Methylcobalamin, according to one source, might be risky for schizophrenic patients." http://www.newmediaexplorer.org/chris/Vitamin%20B12%20vs.%20Alzheimer%20final.rtf

Another one: "Brewer's yeast fortified with B12 is a good source of this nutrient. However, be aware that prolonged and excessive use of brewer's yeast can impair kidney function." http://www.innvista.com/health/nutrition/vitamins/b12.htm

More later...

[Korn]

More about B12/cobalt overload from http://www.acu-cell.com/nico.html :

"Even without having had any Vitamin B12 injections, individuals who run naturally high Vitamin B12 and cobalt levels (which may include patients with mitral valve prolapse), tend to frequently suffer from tachycardia, panic-anxiety attacks, or angina-like chest pains, that may be accompanied by numbness and tingling in the face or extremities.


In contrast to cellular measurements, blood tests for cobalt or Vitamin B12 levels (including the Schilling test) are not only very unreliable, but at times alarmingly wrong, subjecting patients to improper therapy, or routinely misdiagnosing them as Psychiatric Cases, when in fact correcting their abnormal cobalt, Vitamin B12 and nickel status (or ratios) could resolve the problem."

[Korn]

From 'Nutrition for Vegetarians' by drs. Agatha and Calvin Trash (the updated version with updates and corrections, 1996):

"Generally the routine use of vitamin B12 supplements are not advised. In animals studies, there have been cases of increased cancer production in animals receiving high levels of B-12. It has been noted that the animals have an increased production of white blood cells such as occurs in chronic myelogenous leukemia. A case has been reported of acute myeloblastic leukemia resulting from B-12 overdose in the treatment of pernicious anemia.

A group of French investigators reported a series of cases suggesting that B-12 may stimulate multiplication of cancer cell division in general and certain tumor cells in particular.

Patients with rheumatoid arthritis present serum B-12 levels significantly higher than normal subjects.

It is also known to be higher in patients with ulcerative colitis, leukemia and other serious illnesses. A high serum B-12 level should be a signal for a thorough medical evaluation."

Drs. Trash use the word 'vegetarian' in the original meaning of the word, not as in 'lacto-vegetarian', and strongly advice against using eggs and milk.

[i_like_deer]

my roommate had some B12 supplements that had some outrageous RDA value (33,333% ) & so we had taken to biting off little crumbs of them so as not to overdose. However....i still had no idea how much i was taking. i had been having severe dizzy spells for a while but i was really stressed out at the time & i thought it was just that. & i finally realized that i got the dizzy spells after having taken the B12 supplements. i've stopped taking any B12 supplements & the dizzy spells are gone.

[veganmike]

33,333% of RDA is 1,000 mcg of B12 and there are bigger doses available on the US market. People who lack the intrinsic factor necessary for absorption of B12 can take 1,000 mcg of B12 orally and still absorb some of it.

I take 100 mcg daily and feel perfectly fine.

[veganmike]

my roommate had some B12 supplements that had some outrageous RDA value (33,333% ) & so we had taken to biting off little crumbs of them so as not to overdose.

Oh, i don't think you could overdose B12 using 1000 mcg.

I checked on PubMed and there is not a single article on B12 overdose.

[Korn]

I checked on PubMed and there is not a single article on B12 overdose.

Hi Mike, what comments do you have to the other quotes above, if you have any - or do you simply prefer to ignore them? :)

[Korn]

According to this (http://cancerweb.ncl.ac.uk/cgi-bin/omd?query=cobalt&action=Search+OMD) site, cobalt excess in humans can lead to erythrocytosis (an abnormal elevation in the number of red blood cells.) I don't know what threshold that would defined as excessive.

[Korn]

According to this (http://www.sciencedaily.com/releases/2001/10/011030225654.htm ) site, Yale School of Medicine researchers have found that a diet high in cholesterol, animal protein and vitamin B12 is linked to risk of a specific type of cancer of the stomach and esophagus that has been increasing rapidly.

[Korn]

According to this (http://www.ynhh.org/healthlink/cancer/cancer_12_01.html) site, diets high in dietary cholesterol, animal protein and vitamin B12 were associated with a higher risk of four types of cancers: esophageal squamous cell carcinoma, ESCC, noncardia gastric adenocarcinoma, (NGA), esophageal adenocarcinoma (EAC) and gastric cardia carcinoma (GCC).

[Gorilla]

i was looking at the B12 supplements in a health food shop yesterday, they were selling tablets containing 100,000 times the RDA, and the label recommended taking one every day. why would anyone need to take that much B12???!!!

[Korn]

Yes, too much B12 is not good - and of course, to little is bad as well.

I found this today at http://psa-rising.com/eatingwell/vb12_folate04.html

"Folate and B12 were expected to be protective against prostate cancer, because folate, vitamin B12 and homocysteine are essential for methyl group metabolism and thus also for DNA methylation. Abnormal methylation, primarily hypermethylation of certain genes including tumor suppressors, has been implicated in prostate cancer development.


But in fact, increasing plasma levels of folate and vitamin B12 were statistically significantly associated with increased prostate cancer risk, with an odds ratio of 1.60 for folate and 2.63 for vitamin B12 for highest vs. lowest quartile."

[LyricSarah]

a while back i was chewing this b12 gum stuff all the time....I would chew like 4 in a row...because I was treating it like normal gum, nt a supplement...i got SO sick! I was dizzy, my heart was racing like crazy..I felt like I wasnt thinking clearly...I quickly threw out all the rest of the gum that I had left...Im just gonna stick to my multi...which is really good

[1vegan]

a while back i was chewing this b12 gum stuff all the time....I would chew like 4 in a row...because I was treating it like normal gum, nt a supplement...i got SO sick! I was dizzy, my heart was racing like crazy..I felt like I wasnt thinking clearly...I quickly threw out all the rest of the gum that I had left...Im just gonna stick to my multi...which is really good

What kind of sweetener did that gum contain and how much of it ?

(could have been a sugar high ? )

[LyricSarah]

What kind of sweetener did that gum contain and how much of it ?

(could have been a sugar high ? )

It was sweetened with xylitol (sp.?)

[Korn]

From http://www.feinberg.northwestern.edu/nutrition/factsheets/vitamin-b12.html :

"Vitamin B12 is not toxic in oral doses up to 100 mcg daily because absorptive efficiency decreases with increased dose.

The upper limit of safety for vitamin B12 has not been determined due to lack of data substantiating adverse effects at high intakes. The Food and Nutrition Board of the Institute of Medicine recommends that vitamin B12 should be consumed only from food sources to prevent intake of potentially toxic levels."

[Korn]

From http://www.althealth.co.uk/services/info/supplements/vitamin_b12_1.php:

Large doses of vitamin B12 should be used with caution in those with low blood levels of potassium (due to diuretic drugs or other causes).

[Korn]

You may have seen that large doses ofvitamin C may destroy / prohibit B12 intake, and you may also have seen that this is not correct...

Here is a site that claims that 'When (B12 is) taken in conjunction with large doses of vitamin C, nosebleeds, ear bleeding, or dry mouth may occur.' http://www.dreddyclinic.com/vitamins/Vitamin-B12-Cyanocobalamin.htm

Does anyone know here know more about this?

[Korn]

According to http://www.isn.net/~deighanj/v&m-pag2.htm, 'there are reports that supplementation with vitamin B12 may induce an acne like eruption on the skin or worsening of acne if present.'

ETA: The above link seems dead, here's another one: http://www.livestrong.com/article/507637-why-does-vitamin-b12-cause-acne/

[1984]

Hey Korn, do you think it's wiser to take a large dose once a week, say like 2000 mcg's, or a small dose every day , like 100 mcg's?..Just wondering, you seem to be the man with the answers on B12

[Korn]

A small dose (or several even smaller doses) pr. day is better if you need B12 supplements and are not in a desperate need to increase your B12 levels rapidly. B12 is best absorbed in small amounts.

100 mcg pr. day is actually a pretty high dose, unless you have a deficiency. But of course, it all depends on to which degree you are exposed to the many well-known B12 killers....

Normally, the only general advice I think is wise to give, is not to take any general advice, but to take a MMA, homocysteine and B12 serum (blood) test. You never know if you have very low or very high levels of B12 until you have tested this. Some people switch to a vegan diet because they feel they lack energy, and are maybe severely B12 deficient even before the eat the first vegan meal....

[spo]

You may have seen that large doses of vitamin C may destroy / prohibit B12 intake, and you may also have seen that this is not correct...

Here is a site that claims that 'When (B12 is) taken in conjunction with large doses of vitamin C, nosebleeds, ear bleeding, or dry mouth may occur.' http://www.dreddyclinic.com/vitamins/Vitamin-B12-Cyanocobalamin.htm

Does anyone know here know more about this?
Hi, Korn
I just read a study in one of my husband's journals that conducted research in supplementing B12 in deficient adults. In the course of the article, it mentioned that non-deficient adults could safely take large doses of B12 without any side effects. The amounts mentioned were 500 mcg. a day. They were not necessarily recommending taking that large a dose, but were just pointing out that B12 has not been shown to be toxic at high doses.

I did a search to see if anything turned up regarding the Vit C issue, and I found nothing. I, myself, have been taking very large doses of both water soluble and oil soluble Vit C for over 20 years, along with about 50-100 mcg of B12 a day. I have never had a bleeding problem, and all my blood tests are normal.

I spoke briefly to my husband about this, and he said he will look it up, but, he, too, had never heard anything about this being a problem.
spo

[spo]

According to http://www.isn.net/~deighanj/v&m-pag2.htm, 'there are reports that supplementation with vitamin B12 may induce an acne like eruption on the skin or worsening of acne if present.'
Regarding this issue, I will have to do a search, but again, it is something that I never have run into in the course of my studies. I did not ask my husband if he heard about this, but I will. If I find out anything, I will post about it.

There is something that is in the back of my mind about rashes seen in babies and children who were deficient in B12 and were supplemented. I will talk to one of my friends who is a Pediatrics nurse to see if there is info on this.
spo

[1984]

A small dose (or several even smaller doses) pr. day is better if you need B12 supplements and are not in a desperate need to increase your B12 levels rapidly. B12 is best absorbed in small amounts.

100 mcg pr. day is actually a pretty high dose, unless you have a deficiency. But of course, it all depends on to which degree you are exposed to the many well-known B12 killers....

Normally, the only general advice I think is wise to give, is not to take any general advice, but to take a MMA, homocysteine and B12 serum (blood) test. You never know if you have very low or very high levels of B12 until you have tested this. Some people switch to a vegan diet because they feel they lack energy, and are maybe severely B12 deficient even before the eat the first vegan meal....

Interestingly enough, I went to my doctor about 5 months ago and asked him about getting an MMA test done. He said he had never heard of the test before and wasn't even sure if the test was done in Canada. I found that pretty hard to believe, but maybe it goes by another name..? I had just had a blood test done on B12 when I went to see him, and while I didnt neccessarily know the specifics, I knew that it wasnt a reliable test for B12. He had the results from that test in his hand and told me that I had no need to worry about my B12 levels, and there was no need to try another test.

Long story short, I dont trust my doctor, and I'm terrified of the man. He always approaches my diet with hostility. I wish he would just accept what I'm doing and try to help me out with it.

Well I've been taking about 1000mcg's of B12 once a week, and I also get some from rice milk and fortified products. Maybe I should look around and see if I can get a supplement with a smaller dosage, but more importantly, maybe I should try and figure out what my actualy B12 levels are. I'm from a very small town though, and I think it will be hard to find somewhere that will be able to perform a reliable B12 test, or maybe even harder to find a place that has even heard of such a procedure.

[Korn]

I'm from a very small town though, and I think it will be hard to find somewhere that will be able to perform a reliable B12 test, or maybe even harder to find a place that has even heard of such a procedure. There's only one way to change that, you know... ;)