February 27, 2012

Homocysteine and Coronary Heart Disease

(Ivanhoe Newswire) -- Previous studies have suggested that levels of the amino acid, homocysteine, might be an adjustable risk factor for coronary heart disease. However, a recent comprehensive study has found that high blood levels of homocysteine have no meaningful effect on coronary heart disease risks. This makes the previous suggestion of lowering homocysteine with folate acid unbeneficial.

The comprehensive study is made up of 19 unpublished and 86 published studies. The analysis shows that in approximately 50,000 people who have coronary heart disease and 68,000 controls, people who had the MTHFR gene (MTHFR gene is responsible for methylene tetrahydofolate reductase, that uses folate acid to break down and remove homocysteine) that is associated with 20 percent higher blood homocysteine did not have an increase in risk for coronary heart disease.

"The discrepancy between the overall results in the unpublished and the published datasets is too extreme to be plausibly dismissed as a chance finding. Some studies, particularly if small, might have been prioritized for publication by investigators, referees, or editors according to the positivity of their results and some may have been liable to other methodological problems that bias the average of all results. To avoid such biases, we chiefly emphasize the new results from the previously unpublished datasets. The magnitude of the effect of publication bias is substantial and in addition to distorting the association of MTHFR with CHD [coronary heart disease] in published studies, publication bias may also help explain the discrepant findings recently reported for MTHFR and stroke," lead author Robert Clarke from the Clinical Trial Service Unit and Epidemiological Studies Unit at the University Oxford was quoted as saying.

Source: PLoS Medicine, February 2012