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…
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