A perplexing medical paradox now has an explanation according to research undertaken at Barts and The London School of Medicine and Dentistry and 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.
Research led by Dr David Wald at the Wolfson Institute of Preventive Medicine at Barts and The London School of Medicine and Dentistry showed that there was a difference in the reduction in heart disease events between the five trials with the lowest aspirin use (60 per cent of the participants took aspirin) and the five trials with the highest use (91 per cent took aspirin). The observed risk reduction was six per cent but it would have been 15 per cent if no one had been taking aspirin. Research was based on 75 epidemiological studies involving about 50,000 participants and clinical trials involving about 40,000 participants.
"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".
'Reconciling the evidence on serum homocysteine and ischaemic heart disease: a meta-analysis' is published in the Public Library of Science (PLOS One), 2 February 2011.
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Barts and The London School of Medicine and Dentistry
Barts and The London School of Medicine and Dentistry offers international levels of excellence in research and teaching while serving a population of unrivalled diversity amongst which cases of diabetes, hypertension, heart disease, TB, oral disease and cancers are prevalent, within east London and the wider Thames Gateway. Through partnership with our linked trusts, notably Barts and The London NHS Trust, and our associated University Hospital trusts - Homerton, Newham, Whipps Cross and Queen's - the School's research and teaching is informed by an exceptionally wide ranging and stimulating clinical environment.
At the heart of the School's mission lies world class research, the result of a focused programme of recruitment of leading research groups from the UK and abroad and a £100 million investment in state-of-the-art facilities. Research is focused on translational research, cancer, cardiology, clinical pharmacology, inflammation, infectious diseases, stem cells, dermatology, gastroenterology, haematology, diabetes, neuroscience, surgery and dentistry.
The School is nationally and internationally recognised for research in these areas, reflected in the £40 million it attracts annually in research income. Its fundamental mission, with its partner NHS Trusts, and other partner organisations such as CRUK, is to ensure that that the best possible clinical service is underpinned by the very latest developments in scientific and clinical teaching, training and research.