Vegetarians with sub-optimal B12 levels who received daily supplements of the B vitamin displayed improvements in flow-mediated dilation (FMD), a measure of a blood vessel's healthy ability to relax, according to findings published in The Journal of Nutrition, Health & Aging.
Supplements at a dose of 500 micrograms per day were also associated with an improvement in the thickness of arterial walls, indicating that B12 supplementation may offer a “novel strategy for atherosclerosis prevention”.
It is commonly believed that vegetarians have a lower risk of cardiovascular disease, but some data has indicated that vegetarian diets are deficient in vitamin B12, and relatively high in salt, both of which may increase the risk of atherosclerosis, explained the researchers.
Indeed, the same group of researchers has previously reported impaired vascular functioning and thickening of the blood vessel walls in Chinese vegetarians.
“Vitamin B-12 deficiency is prevalent among older people and vegetarians and is mostly asymptomatic. For vegetarians, apart from direct vitamin B-12 supplementation, vitamin B-12 deficiency is also preventable by higher and adequate intake of dairy products, eggs and fortified cereals,” explained the researchers led by scientists at the Chinese University of Hong Kong.
Their new study aimed to test if 12 weeks of supplementation with 500 micrograms per day of vitamin B12 could affect vascular health in 43 healthy vegetarians with an average age of 45.
Participants were randomly assigned to receive placebo or the supplements. After completing the intervention, a ten week ‘washout’ period was observed before the participants were crossed over to the other intervention.
Results showed a significant increase in blood levels of vitamin B12 in the B12 groups, as well as a lowering of homocysteine, an amino acid that at high levels is linked to heart disease.
In addition, B12 supplementation increased FMD from 6.3% to 6.9%, but no such improvements were observed in the placebo group.
Twelve weeks of supplementation also significantly reduced the average thickness of the carotid artery walls from 0.69 to 0.67 mm, added the researchers.
“Vitamin B-12 supplementation in asymptomatic vegetarians with compromized vitamin B-12 status may lead to a significant improvement in arterial endothelial function and carotid intima-media thickness, with potential benefit on cardiovascular health.”
The authors urged caution, however, and added that the participants in the current trial had low levels of B12 at the start of the study. “It is uncertain that vitamin B-12 supplementation will have the same effects in vegetarians with better vitamin B-12 status,” they said.
Source: The Journal of Nutrition, Health & Aging
Published online ahead of print, doi: 10.1007/s12603-012-0036-x
“Vitamin B-12 supplementation improves arterial function in vegetarians with subnormal vitamin B-12 status”
Authors: T. Kwok, P. Chook, M. Qiao, L. Tam, Y. K. P. Poon, A. T. Ahuja, J. Woo, D. S. Celermajer and K. S. Woo