Research undertaken at Barts and The London School of Medicine and Dentistry may have found an answer to a perplexing medical paradox. This research is published in the current issue of the Public Library of Science.
The paradox is that taking folic acid, a B vitamin, lowers homocysteine in the blood which, epidemiological evidence indicates, should lower the risk of heart attack, but clinical trials of folic acid have not shown the expected benefit.
The explanation is surprisingly simple; lowering homocysteine prevents platelets sticking, which stops blood clots...something aspirin also does, so if people in the trials were already taking aspirin there would be no extra benefit in lowering homocysteine with folic acid. Aspirin was in fact widely used by participants in the trials because they were mainly conducted in patients who had already had a heart attack or other cardiovascular diseases.
"The explanation has important implications," said Dr David Wald, the lead author of the paper. "The negative clinical trial evidence should not close the door on folic acid - folic acid may still be of benefit in people who have not had a heart attack because they will generally not be taking aspirin".