Washington, Sept 24 : Researchers in Hong Kong have found that a dietary supplement containing isoflavone - chemical found in soybeans, chickpeas, legumes and clovers - can boost artery function in stroke patients.
Hong Kong researchers' study is said to be the first randomised controlled trial to find out the effects of isoflavone supplement on the way the brachial artery (the main artery in the arm) dilates in response to an increase in blood flow, a phenomenon known as flow-mediated dilation (FMD), in patients with established cardiovascular disease.
Brachial FMD is an indicator of the functioning of the cells that line the inner surfaces of blood vessels (vascular endothelium), and endothelial dysfunction is implicated in cardiovascular disease.
Professor Hung-Fat Tse, William MW Mong Professor in Cardiology and Academic Chief of the Cardiology Division in the Department of Medicine, Queen Mary Hospital, The University of Hong Kong and his team found that 12 weeks of isoflavone supplement, at a dose of 80 mg a day, significantly improved brachial FMD and, therefore, vascular endothelial dysfunction in patients who had suffered an ischaemic stroke (a stroke caused by blood clots or other obstructions).
"These findings may have important implications for the use of isoflavone for secondary prevention in patients with cardiovascular disease, on top of conventional treatments," the authors said.
The trial was a double blind, placebo-controlled trial, involving 50 patients taking the isoflavone supplement, and 52 taking a placebo pill.
The researchers found that 80 per cent of the patients had an impaired FMD of less than 3.7 percent at the beginning of the study, but after 12 weeks of isoflavone or placebo, there was an improvement of one per cent in the isoflavone-treated patients compared with the controls.
"Although the absolute increase in brachial diameter - one per cent - is small, the relative increase actually amounted to about 50 percent because the mean average FMD in these stroke patients was about two per cent. In fact, in patients with severe endothelial dysfunction, there might not be dilatation of brachial diameter at all," Tse said.
Also, the prevalence of impaired FMD after 12 weeks became significantly lower in isoflavone-treated patients than in the controls. There was also a greater effect in patients with more severe endothelial dysfunction.
"The patients who had a lower initial FMD were found, in general, to respond with a larger absolute increase in FMD after receiving 12 weeks of isoflavone intervention, compared to patients who had a better baseline FMD in the first place," Tse said.
"These findings suggest that isoflavone reverses endothelial dysfunction in this group of patients with cardiovascular disease. This has important clinical implications, as the benefit of the treatment is conferred to the group of patients with the highest risks for cardiovascular events, and this effect persists, even at this rather late stage of the cardiovascular continuum," Tse added.
The study is published online in Europe's leading cardiology journal, the European Heart Journal.