Soy products contain isoflavone
A chemical found in soybeans and chickpeas could benefit people who have suffered a stroke, say researchers.
The University of Hong Kong team say the treatment effect of the chemical, isoflavone, is comparable to that of cholesterol-busting statin drugs.
The European Heart Journal study showed isoflavone helped improve blood flow through the arteries.
Previous research has suggested that eating soy may help prevent breast and prostate cancer and lower cholesterol.
Soya isoflavones in particular have been shown to reduce cardiovascular disease risk as they inhibit the growth of cells that form artery-clogging plaque.
All of the 102 patients in the latest trial had suffered a first or recurrent ischaemic stroke -caused by a blood clot - in the previous six months and had established heart disease.
The patients were split into two groups, with one receiving a 12-week course of isoflavone as an 80mg daily dietary supplement, and the other given a dummy pill or placebo.
The scientists measured the way the brachial artery - the main artery of the arm - dilated in response to an increase in blood flow.
This measurement, the flow-mediated dilatation (FMD), is an indicator of the functioning of the cells that line the inner surfaces of blood vessels - the endothelium - which are implicated in cardiovascular disease.
At the start of the study the prevalence of impaired FMD was similar between the two groups.
But after 12 weeks, the FMD improved significantly in the patients given the isoflavone supplement.
Lead researcher Professor Hung-Fat Tse said: "These findings suggest that isoflavone reverses endothelial dysfunction."
He said there were important clinical implications, as the benefit of the treatment was conferred to the group of patients with the highest risks for cardiovascular events, and the effect persisted, even at a rather late stage of disease.
Professor Tse said it was too early to recommend the use of isoflavone supplements.
But he said: "Diets with higher isoflavone contents might be beneficial in reducing cardiovascular risk in ischaemic stroke patients."
He said the mechanism by which isoflavone produces these changes in FMD were still not completely understood.
Isoflavone is a major class of phytoestrogens, naturally occurring chemicals that mimic the effect of the human hormone oestrogen. Oestrogen is known to protect against heart disease.
Dr Peter Coleman from The Stroke Association said: "This is an important and interesting study showing that dietary supplementation with isoflavones in people who have had a stroke may reduce their risk of further stroke or cardiovascular disease.
"Whilst this is a positive finding, it was a small study and further research is needed to discover how plant isoflavones could reduce stroke risk."