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WebMD reports:

In the July issue of the American Journal of Clinical Nutrition, German researchers tracked 174 apparently healthy people living in Germany and the Netherlands.

They found that 92% of the vegans they studied -- those who ate the strictest vegetarian diet, which shuns all animal products, including milk and eggs -- had vitamin B12 deficiency.

That article refers to this study that states:

Of the 3 groups, the vegans had the lowest vitamin B-12 status. In subjects who did not consume vitamins, low holotranscobalamin II (< 35 pmol/L) was found in 11% of the omnivores, 77% of the LV-LOV group, and 92% of the vegans.

This other study says:

Higher rates of deficiency were reported among vegans compared with vegetarians and among individuals who had adhered to a vegetarian diet since birth compared with those who had adopted such a diet later in life.

Are the vast majority of Vegans Vitamin B12 deficient?

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    I posted the links so that you can get some pointers from related research. B12 deficiency has to be defined in some way, it may be the case that levels for optimal health should be quite a bit higher than the levels were overt deficiency starts. This means that studies that look into homocysteine levels, and more generally mortality rates are also important. So, basically, you are tackling two problems at once, it's not just how many vegans are below some B12 level, but also how one should choose this level. – Count Iblis May 3 '16 at 2:03
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    @RPBCL: I think we might be at cross-purposes. When you ask a question, we ask nicely for some links to notable claims to show this is a real claim people make, and to make sure the OP hasn't merely misunderstood a joke or other claim. Those links don't have to be to studies. Newspaper articles, popular tweets, political speeches, etc, are all good fodder. (In answers, we expect much better quality sources.) – Oddthinking May 3 '16 at 3:30
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    Because you have done a good job at researching the info already, you have set a high standard for the answers. They have to provide better references than what you've already provided to support/refute the claim. – Oddthinking May 3 '16 at 3:36
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    @RPBCL: No, it isn't a bad thing at all, but I think the chance of you getting an answer is lower - you already found the two obvious papers that would normally be sufficient to provide an answer. – Oddthinking May 3 '16 at 5:56
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Summary

The evidence about the prevalence of vitamin B12 deficiency in vegans comes mainly from this review of studies in EJCN, 2015:

  • The results differed widely (2.4-78%) among studies, but 45% of vegans in average were B12 deficient, based on low blood B12 levels.
  • More than 85% of vegans who were not taking B12 supplements were B12 deficient, based on low blood B12 levels. (Why not 100%? Because, at the time of a study, some participants were on a vegan diet for only 1 or 2 years, which may be too short to develop deficiency).

Evidence

1) In various studies described in The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature (EJCN, 2015) (summarized in Table 1), the percent of vegans with B12 deficiency (by the criteria of low B12 (cobalamin) levels, which ranged widely from <95 to <250 pmol/l) were 2.4 to 78%.

2) In the study mentioned in the question: Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians (AJCN, 2003), which included only 29 vegans, 27 of them or 92% were B12 deficient on the basis of low holotranscobalamin II levels (<35 pmol/l), but only 52% on the basis of low cobalamin levels (<156 pmol/l).

Lab tests for vitamin B12 deficiency

According to Institute of Medicine (US), blood levels of vitamin B12 (cobalamin) that reflect deficiency are 120 to 180 pmol/L (170 to 250 pg/mL) for adults. But, as deficiency develops, blood levels may be maintained at the expense of B12 in the tissues. Thus, normal blood levels do not necessarily indicate adequate B12 status.

Methylmalonic acid (MMA) levels may more accurately reflect the B12 status, because they indicate a metabolic change that is highly specific to B12 deficiency (Office of Dietary Supplements). Blood levels <270 nmol/l are normal (The Vegan Society).

Time in which vitamin B12 deficiency can develop

According to Vegan Society:

In the absence of any apparent dietary supply, deficiency symptoms usually take five years or more to develop in adults, though some people experience problems within a year. A very small number of individuals with no obvious reliable source appear to avoid clinical deficiency symptoms for twenty years or more.

The recommended dietary allowance (RDA) for vitamin B12 for adults is 2.4 µg/day. It is not clear at which lower daily intakes deficiency could develop, but vegetarians, who consume milk with 1.1 µg B12/cup (237 mL) and eggs with 0.6 µg B12 also often develop deficiency (EJCN, 2015).

Prevention of vitamin B12 deficiency in vegans

It seems that for most vegans, the only option to prevent B12 deficiency is to consume B12 fortified foods or supplements. Some plant foods contain vitamin B12, but this is either inactive (in spirulina, chlorella, tempeh, miso, kombu) or not present in sufficient amounts (in white button mushrooms, Korean purple laver or nori or nutritional yeast); human intestinal bacteria may also produce some vitamin B12 but not in sufficient amounts (Vegan Health, Vegetarian Nutrition Dietetic Practice Group).

Vitamin B12 deficiency in vegans who do not take supplements

  1. AJCN, 2003, Table 1: 29% (5 from 17) of vegans who were taking B12 supplements and 83% (10 from 12) of those who were not, were B12 deficient.
  2. Annals of Nutrition and Metabolism, 1983: From 83 participants (vegetarians/vegans), 92% of vegans who were not taking supplements, 64% of the lactovegetarians, 47% of the lacto-ovovegetarians and 20% of the semivegetarians had low serum vitamin B12 levels (<200pg/ml or <150 pmol/L). However, their complete blood count values did not deviate greatly from those found for nonvegetarians (no anemia), even though some had been vegans or lactovegetarians for over 10 years.
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  • So, a large part of the evidence says "supplementing B12 ~effectivly prevents deficiency"? The way the claim is framed any analysis must look just for strict veganism without pills. Although the title seems to look a 'epidemiologically found' this cannot be used to draw any meaningful conclusions, as the veganism that should be under the loupe is a diet, not a pharmaceutical intervention. This looks at veganism as an upper-class capitalist lifestyle. Add to that internal stores: the most interesting point is B12-level in true vegans w/o pharmacy shopping after 20 years of observance. – LangLаngС Dec 6 '19 at 12:21
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    "As is" Q is exactly that: not very "interesting", since we look for actual 'unclean' practices. That is: seeing that B12 caring pillpoppers still have problems is indeed valuable. But I still suggest to really frame-challenge this into two clearly separated sections: 1 looking at self-reported vegans and their confounded status with pills 2 actual vegans (zero pills) and their status. (Knowing that the literature on this isn't that ample). Pure veganism is a major challenge in any case. – LangLаngС Dec 6 '19 at 17:00
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    I work with a group of boyscouts. There are a few parents on that group that went all-natural vegans (as in, no supplementation of any kind). The difference on their kids towards the non-vegan kids is rather remarkable - they are usually the least energetic, most pale, weak and mentally underdeveloped of the bunch. They are also sick quite often. This was also observed elsewhere – T. Sar Dec 10 '19 at 11:27
  • I do feel this answers my question as I've stated it. Thanks for this researched answer. – RPBCL Dec 15 '19 at 4:23

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