Researchers reported that news today at the American College of Cardiology's annual meeting.
The researchers studied data from more than 5,000 Americans who were followed for 20 years, starting when they were 18-30 years old.
They filled out dietary surveys, which showed a blood pressure benefit for people who ate the most isoflavones. Their systolic blood pressure (the first number in a blood pressure reading) was, on average, 5.5 points lower than people who ate the least amount of isoflavones.
It's fairly easy to add isoflavones to your diet, says researcher Safiya Richardson, a graduating medical student at Columbia University. An 8-ounce glass of soy milk has about 22 milligrams of isoflavones, and 100 grams of roasted soybeans have as much as 130 milligrams.
Here's how it might work. Isoflavones boost production of enzymes that make nitric oxide, which helps relax blood vessels and lower blood pressure, Richardson says.
Her study does not prove that isoflavones made all the difference. People who eat a diet rich in isoflavones might have other advantages that weren't measured, or a healthier lifestyle overall, says John Harold, MD, a UCLA heart specialist and American College of Cardiology vice president.
Larger studies are needed to see if the results hold up.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.