I just updated Mild B12 Deficiency – Cardiovascular Disease & Homocysteine with the following from a study that just came out:
A 2012 randomized, placebo-controlled, crossover clinical trial tested B12 supplementation’s effects on flow-mediated dilation (FMD) of the brachial artery and intima-media thickness (IMT) of the carotid artery, both of which are markers of cardiovascular disease (1). The study was done in Hong Kong and there were 50 vegetarians, two of whom were vegan. Twelve subjects (24%) had serum vitamin B-12 between 203-406 pg/ml and 35 subjects (70%) < 203 pg/ml. After 12-week periods of 500 µg of B12 per day, average homocysteine levels went from 16.7 to 11.3 µmol/l. Brachial artery FMD significantly increased and carotid IMT significantly decreased, both of which improves cardiovascular function, after vitamin B12 but not after placebo treatment. These positive effects appeared to be better correlated with the correction of vitamin B12 deficiency than with the lowering of homocysteine. The authors noted that the effects “on carotid intima-media thickness was quite subtle and of uncertain biological significance.”
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I was surprised that with 500 µg B12 per day, homocysteine levels did not decrease even further, especially since these participants were shown to have good folate status. The study contained no control group of non-vegetarians, so it’s not clear if the same results would be found for non-vegetarians, though rarely do non-vegetarians have an average homocysteine level as high as 16.7 µmol/l.
In any case, this appears to be the first direct evidence on cardiovascular function to show that mild vitamin B12 deficiency could have a negative effect.
None of the participants experienced side effects, including skin reactions, while on the B12 supplementation regimen.
1. Kwok T, Chook P, Qiao M, Tam L, Poon YK, Ahuja AT, Woo J, Celermajer DS, Woo KS. Vitamin B-12 supplementation improves arterial function in vegetarians with subnormal vitamin B-12 status. J Nutr Health Aging. 2012;16(6):569-73. | link