The chemical called Isoflavone is also found in chickpeas, legumes and clovers. The current study had 50 patients taking 80 milligrams of the isoflavone supplement, and 52 patients on placebos.
After 12 weeks, the researchers found improved blood flow in brachial artery, which is the main artery in the arm.
"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 researchers wrote.
The details of the study appear in the European Heart Journal.