Are the vast majority of vegans Vitamin B12 deficient?

Question

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?

Answer 1

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.