It's unclear how soybean products might reduce blood pressure. One theory, according to the researchers, is that soy proteins widen blood vessels while helping the body do a better job of processing blood sugar.

"They should wait and see. They shouldn't change their diet based on the current state of the science," said Dr. Jeffrey Cutler, a scientific adviser with the National Heart, Lung, and Blood Institute.

Soybean products, a staple of Asian diets, have long been a favorite of health advocates. Researchers have shown that food items like tofu and soy milk can reduce cholesterol levels and lower risks for cancer, heart disease and osteoporosis, said Jeannie Moloo, a spokeswoman for the American Dietetic Association.

Average Blood Pressure Levels Dropped

In this latest study, a team of American and Chinese researchers tracked the health of 302 Chinese patients with early signs of high blood pressure or full-blown hypertension.

The research team randomly assigned the participants to one of two special diets: members of one group ate 40 grams of soybean protein supplements per day while the others ate the same amount of wheat-based carbohydrates. Both the soy and wheat came readymade in cookie form.

The findings of the study appear in the July 5 issue of the Annals of Internal Medicine.

Among those in the soy group who finished the study, average blood pressure levels dropped from 135/85 mm Hg to 131/82 mm Hg, the researchers report. According to a commentary accompanying the study, however, the blood pressure drop observed among the "pre-hypertensive" group -- individuals deemed likely to develop serious blood pressure -- wasn't significant.

The researchers -- led by Dr. Jiang He, of Tulane University -- said it's unclear how soybean products might reduce blood pressure. One theory, according to the researchers, is that soy proteins widen blood vessels while helping the body do a better job of processing blood sugar.

Tried-and-True Strategy

So, should Americans start stocking up on soy products at the health-food store? Not necessarily, said Cutler, who also co-wrote a commentary on the findings.

He pointed out that other research has linked high soy consumption to bladder cancer. And he noted that amount eaten by subjects in various studies -- equivalent to one or two soy burgers and one to four cups of soy milk a day -- is definitely large.

For now, Cutler believes that people who have high blood pressure or are in danger of developing it should stick to the tried-and-true strategy of consuming a low-fat, low-salt diet along with exercise, and medication if necessary.

Soy products do appear to be healthy in small amounts, however. Moloo suggested that products like tofu, despite its bland reputation, can actually taste delicious, replacing meats like beef and chicken.

More information: Learn more about high blood pressure at the American Heart Association.