Eating raisins and soy appears to help ward off high blood pressure, a key risk factor in heart disease, according to two studies presented at a major US cardiology conference on Sunday.
Munching on a handful of raisins three times a day helped people with slightly elevated blood pressure lower their numbers after several weeks, said one of the studies presented at the American College of Cardiology conference.
The randomized clinical trial -- believed to be the first formal measurement of raisins' benefits on blood pressure -- involved 46 people with a condition known as pre-hypertension.
That means their blood pressure ranged from 120 over 80 millimeters of mercury (mm Hg) to 139 millimeters of mercury over 89 mm Hg, or just higher than normal.
Compared to people who snacked on cookies or crackers, the raisin-eating group saw significant drops in blood pressure, in some cases lowering the top number, or systolic pressure, by 10.2, or seven percent over the 12-week study.
Researchers are not sure exactly why the raisins work so well, but they think it may have to do with the high level of potassium in the shriveled, dried grapes.
"Raisins are packed with potassium, which is known to lower blood pressure," said lead investigator Harold Bays, medical director of Louisville Metabolic and Atherosclerosis Research Center.
"They are also a good source of antioxidant dietary fiber that may favorably alter the biochemistry of blood vessels, causing them to be less stiff, which in turn, may reduce blood pressure."
A handful of about 60 raisins contains a gram of fiber and 212 milligrams of potassium. Raisins are often recommended as part of a high-fiber, low-fat diet to reduce blood pressure.
A second study on soy showed that daily intake of foods like tofu, peanuts and green tea helped lower blood pressure in more than 5,100 white and African American people aged 18-30.
The study began in 1985 and was based on self-reported data about the food the participants ate.
Those who consumed about 2.5 or more milligrams of isoflavones, a key component in soy, per day had significantly lower systolic blood pressure -- an average of 5.5 mmHg lower -- than those who ate less than 0.33 mg per day.
That daily level should not be hard for most people to reach -- a glass of soy milk contains about 22 mg of isoflavones, or nearly 10 times the amount needed to see an effect, according to the research.
"Our results strongly suggest a blood pressure benefit for moderate amounts of dietary isoflavone intake in young black and white adults," said Safiya Richardson, a graduating medical student at Columbia University's College of Physicians and Surgeons and the study's lead investigator.
"Our study is the first to show a benefit in African Americans, who have a higher incidence of high blood pressure, with an earlier onset and more severe end-organ damage."
Eating soy could be a way for people with slightly elevated blood pressure to avoid progressing to high blood pressure, and potentially ward off the need to take medications, she added.
"Any dietary or lifestyle modification people can easily make that doesn't require a daily medication is exciting, especially considering recent figures estimating that only about one third of American hypertensives have their blood pressure under control."
Soy and the isoflavones it contains work by boosting enzymes that create nitric oxide, which in turns helps to widen blood vessels and reduce blood pressure.
"Based on our results and those of previous studies, we would encourage the average adult to consider including moderate amounts of soy products in a healthy, well-balanced diet to reduce the chances of developing high blood pressure," Richardson said.