I've read in several health sites that state that high blood homocysteine, as well as low B12 intake, is not only correlated, but actually causes cardiovascular diseases. In order to verify those claims, I've looked for related studies and found controversial results. This one, for example, observed no positive effects from B12 supplementation:
In this randomized double-blind trial, high-dose vitamin therapy had no effect on the outcome measures of stroke, CHD events, or death.
The author speculates several possibilities for the negative results, including that high homocysteine levels could be merely correlated, but not actually causing the problem.
I wonder if there have been advancements on that matter. Is it known whether low B12 causes cardiovascular diseases, or is merely correlated? If it is just a correlation, then what is causing both low B12, high homocysteine and increased cardiovascular disease? In particular, have any study observed if a diet rich in red meat, for example, has the positive effects that pure supplementation failed to show?