Soy Study May Show Link To Lower Blood Pressure

Funded by the National Institutes of Health, the study is investigating the effect of chemicals in the soy plant, isoflavones, in reducing hypertension in menopausal women. Another two-year study is examining the effect of these same soy isoflavones on osteoporosis in menopausal women.

"There doesn't appear to be any downside to soy," said Dr. Addison Taylor, professor of medicine at BCM. "We should have some idea at the end of the study on how much soy isoflavones lower blood pressure and also on the ways in which this effect occurs."

BCM researchers are particularly interested in isoflavones that are part of a group of chemicals called phytoestrogens, which are abundant in soy plants, because they may lower blood pressure. Taylor and his colleagues are examining the effect of isoflavones on the production of nitric oxide, a substance made by blood vessels that reduces the tendency of blood to clot.

The six-week trial will administer enriched isoflavones to patients, who will undergo monitoring of blood pressure for an entire 24-hour period. Patients will be equipped with an automatic device that will measure blood flow using an elastic armband filled with mercury.

"It will give us a better idea as to whether this beneficial effect persists through the whole 24 hours or is confined to just certain parts of the day or night," said Taylor, a co-investigator of the study headed by Dr. William Wong, professor of pediatrics at BCM and researcher at the Children's Nutrition Research Center. "It will also allow us to determine what role nitric oxide production is playing."

Isoflavone has long been believed by some members of the scientific community to ward off health problems associated with aging, such as hot flashes in menopausal women; but limited empirical data have prevented physicians from recommending its use. However, concerns about conventional estrogen replacement therapy, based on its connection to an increased risk of breast cancer, have compelled many women to consider "natural" alternatives such as soy.

Taylor anticipates that isoflavone tablets will be commercially available some day either as a drug or as a food supplement. The soybean in its natural state does not yield nearly the same medicinal effect that extracted, enriched concentrations of isoflavone do.

"I would suspect that this will still be labeled as a food additive but hopefully with better quality control than some of the other botanical products currently being sold," Taylor said. "The more information we have, the more we can at least tell the medical community about what to expect when these agents are used."

Taylor is still actively recruiting study participants. Healthy menopausal women with blood pressures between 130/80 and 160/100 who are not taking hypertensive medication may call 713-798-6783 for enrollment information.