One half cup of soy nuts each day may work as well as anti-hypertension medication to lower blood pressure, a new study in postmenopausal women demonstrates.
And women with moderately elevated blood pressure - a condition known as pre-hypertension - also showed reductions in their blood pressure after eight weeks of eating soy nuts, cardiologist Francine Welty and her colleagues at Beth Israel Deaconess Medical Centre in Boston found.
"We know that people in the pre-hypertension group are at increased risk of cardiovascular disease," Dr. Welty said. "This would provide a dietary treatment that could safely lower blood pressures in that pre-hypertensive range."
Studies are still under way to determine if people with pre-hypertension should take drugs to lower blood pressure.
Dr. Welty and her research team recruited 60 postmenopausal women, 12 of whom had hypertension, to begin a Therapeutic Lifestyle Changes diet that involved cutting fat, cholesterol, sodium and calories.
Each participant in the study spent eight weeks on the TLC diet alone and eight weeks on the TLC diet plus a half cup of dry-roasted, unsalted soy nuts daily.
While eating the soy nuts, the women subtracted the equivalent amount of protein from other sources so that their protein consumption remained constant.
The researchers chose soy nuts, Dr. Welty noted, because they are among the least-processed sources of soy available and are more convenient and portable than either soy milk or tofu.
The women eating the soy nuts had a drop in systolic blood pressure (the top number of the blood pressure reading) of 9.9 per cent, and a drop in diastolic blood pressure (the lower number) of 6.8 per cent.
Among those with pre-hypertension (systolic blood pressures between 120 millimetres of mercury and 139 mmHg), the soy nuts decreased systolic blood pressure by 5.5 per cent and diastolic blood pressure by 2.7 per cent.
For women with normal blood pressure, the nuts also lowered systolic blood pressure by 4.5 per cent and diastolic pressure by 3 per cent.
Women also showed an 11-per-cent reduction in their low-density lipoprotein (LDL) or "bad" cholesterol.
Two similar studies - one using soy milk, the other soy cookies - also found that soy reduces blood pressure, Dr. Welty noted. In the soy nut study, people ate three or four portions of the nuts throughout the day, rather than eating the entire allotment in a single sitting.
This probably kept a steady level of the beneficial component of soy in the body, Dr. Welty said.
The researcher said she would recommend people include soy nuts and soy milk in their diet to help lower their blood pressure.
"If the findings are repeated in a larger group, they may have important implications for reducing cardiovascular risk in postmenopausal women on a population basis," the study concluded.