According to a meta-analysis published in the September issue of Neurology, the most widely read and highly cited peer-reviewed neurology journal, supplementation with B vitamins lowered homocysteine levels and reduced the risk of stroke among certain populations.
Homocysteine is an amino acid that is not a protein; high levels of homocysteine have been linked to inflammation and cardiovascular disease. Scientists involved in the research broke down the results into different groups, noting that there was an overall 8% reduction of stroke risk for individuals with three or more years of follow-up and a 9% reduction in risk for individuals not consuming foods already fortified with folate (often called B9).
Although this meta-analysis and some previous research indicates no reduction in stroke risk attributable to B12 supplementation, it is useful to note that the B12 supplement generally employed in trials is cyanocobalamin, which is less bioavailable than methylcobalamin. In fact, several studies on the amelioration of neurological and other physical disorders report improved metabolic processes through methylcobalamin supplementation.
This is unsurprising, given that researchers discovered back in 1969 that grouping all cobalamins together under the heading of "serum B12" was misleading, and masked health differences between people with higher levels of methylcobalamin and people with higher levels of, for example, hydroxocobalamin.
In an article published in the March 1969 issue of the Journal of Clinical Pathology, the researchers noted, "a normal figure for total serum B12 might ... mask a deficiency of physiologically active cobalamins [such as methylcobalamin], owing to their conversion to cyanocobalamin, which is without enzyme function and is readily excreted -- a state of affairs which might lead to hematological and neurological disorders."
Back in 1969, researchers hypothesized that cigarette smoking and other behaviors might cause excessive cyanide consumption, which could "trap" a great deal of B12 as cyanocobalamin, which is lost to the body through excretion and has near-zero beneficial effects. It seems particularly unfortunate that cyanocobalamin is the form of B12 so often chosen to determine whether B12 supplementation has any health benefit, given how many years this particular form of B12 has been known to be without substantive metabolic value.
Although B12 is frequently delivered through subcutaneous injections, it is possible to consume methylcobalamin supplements in the form of vitamin lollipops such as revitaPOP, as well as in liquid formulations. The Allentown Health Examiner anticipates more clinical research on the health effects of supplementation with bioavailable B12: methylcobalamin.