Meta-Analysis of Vegans & Homocysteine

Isn’t it great to be living in a time where there have been so many studies on homocysteine levels of vegans that someone can do a meta-analysis? We have officially arrived.

This past week, such a study was released by a team from the University of West London, School of Psychology, Social Work and Human Sciences. I have tracked most of this research, so their findings that vegans have higher homocysteine levels due to low B12 status came as no surprise. They included results from six cohort and eleven cross-sectional studies.

Ideally, you want your homocysteine levels below 10 µmol/l, with above 15 µmol/l being strongly associated with increased chronic disease (cardiovascular disease and early death).

The average homocysteine levels in the studies were (µmol/l):

omnivore – 11.0
lacto-ovo vegetarian – 13.9
vegan – 16.4

Average vitamin B12 levels were (pmol/l):

omnivore – 303
lacto-ovo vegetarian – 209
vegan – 172

This was no surprise as most of the vegans in these studies were not taking vitamin B12 supplements or eating fortified foods, B12 being an important part of keeping homocysteine levels in check (see Mild B12 Deficiency – Cardiovascular Disease & Homocysteine for more information).

However, there were a couple things that the authors concluded that did raise my eyebrows.

They expressed skepticism that fortified foods can prevent elevated homocysteine levels in vegans, due to the fact that fortified foods contain cyanocobalamin, rather than methylcobalamin. The authors said that it takes four to nine weeks for cyanocobalamin to be converted into methylcobalamin, the form needed to lower homocysteine.

Readers of my blog probably know that only in rare circumstances do I think it’s necessary to supplement with methylcobalamin rather than cyanocobalamin. I will address these author’s concerns in an upcoming post.

In discussing the one study that showed vegans to have healthy homocysteine levels, the authors say:

“The study by Haddad et al. concluded that, statistically, vegans had similar plasma tHcy to omnivores (i.e. 8·0 against 7·9 mmol/l, respectively) and serum vitamin B12 levels (i.e. 313 against 312 pmol/l, respectively). In this case, it was noted that 36 % of the participating vegans were users of vitamin B12 supplements, although the type, dosage and frequency of usage were not reported.”

However, Haddad et al. did give the average amount of vitamin B12 intake for the vegans and it was 6.0 µg for the vegan women and 5.0 µg for the vegan men (2). And the possibility that any of it wasn’t cyanocobalamin is low.

Stay tuned for more on the cyano wars…

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Vegan for Life: Everything You Need to Know to Be Healthy and Fit on a Plant-Based Diet from


1. Obersby D, Chappell DC, Dunnett A, Tsiami AA. Plasma total homocysteine status of vegetarians compared with omnivores: a systematic review and meta-analysis. Br J Nutr. 2013 Jan 8:1-10. [Epub ahead of print] | link

2. Haddad EH, Berk LS, Kettering JD, Hubbard RW, Peters WR. Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr. 1999;70(suppl):586S-93S. | link

4 Responses to “Meta-Analysis of Vegans & Homocysteine”

  1. Derek Says:


    Why is methylcobalamin always mentioned as the “better” form of B12, but rarely the other bioactive form, adenosylcobalamin? And why is the latter (referred to as dibencozide) the form pushed by bodybuilding supplement makers?

    And while we’re at it, why does adenosylcobalamin have two names?

    Just wondering.

  2. Jack Norris RD Says:


    Good questions that I don’t know the answers to. A quick Internet search didn’t give me an answer.

  3. John Says:

    Jack, I think a better question is why you are so concerned with saying that cyanocobalamin is the one we should take? Check this out:

    “Several biological effects may help to explain the harmful effect of B vitamins in patients with impaired renal function. High levels of folic acid not metabolized to tetrahydrofolate could increase levels of asymmetric
    dimethylarginine , an antagonist of nitric oxide. In addition,
    patients with renal failure who are given cyanocobalamin
    accumulate cyanide, and cyanide, excreted as thiocyanate,
    has a central role in the catabolism of hydrogen sulphide,
    an endothelium-derived relaxing factor analogous to nitric

    Among patients with renal failure who were given
    methylcobalamin rather than cyanocobalamin, levels of both plasma total homocysteine and asymmetric dimethylarginine
    were lowered.”

    So… methylcobalamin is the only form that consistently works and works effectively. Stop slagging it off. 😉

  4. Jack Norris RD Says:


    This is why:

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