Soy nuts have a lot to offer postmenopausal women, suggest two studies conducted by Francine Welty and her team from the Beth Israel Deaconess Medical Center, Boston.
Enjoying a half-cup of soy nuts as one source of protein in a healthy diet can reduce blood pressure and LDL cholesterol levels in postmenopausal women by as much as 10% in just 8 weeks, discovered Welty's team in research they published in the Archives of Internal Medicine (Welty FK, Lee KS, et al.)
High blood pressure (hypertension) is defined as having blood pressure higher than 140/90 mmHg, and is a major risk factor for cardiovascular disease, a leading cause of death in postmenopausal women.
In this 16-week study, 60 postmenopausal women (average age 56), 12 of whom had high blood pressure, followed two different diets, each for 8 weeks: a Therapeutic Lifestyle Changes (TLC) diet or a TLC diet in which soy nuts (roasted, unsalted soybeans) were used as one source of protein. Blood samples and blood pressure measurements were taken at the beginning and end of each 8-week diet.
The TLC diet derived 30% of its calories from fat (with 7% or less from saturated fat), 15% from protein and 55% from carbohydrates. The diet delivered 1,200 mg of calcium and less than 200 mg of cholesterol daily. Two meals of fatty fish, such as salmon or tuna, were included weekly.
The TLC with soy diet contained the same calorie, fat and protein, calcium and cholesterol content, but 25 grams of its protein were delivered in the form of one-half cup of unsalted soy nuts.
When eating the soy nuts as part of their TLC diet, the women with high blood pressure experienced systolic and diastolic blood pressure reductions of 9.9% and 6.8%, respectively, and even those with normal blood pressure experienced reductions and 5.2% and 2.9%, respectively.
Not only was blood pressure lowered in all the women, but in those who began the study with high blood pressure, LDL cholesterol and apoB levels also dropped, 11% and 8% respectively, compared with the TLC diet without soy. (LDL, sometimes called "bad" cholesterol is a major risk factor for cardiovascular disease, and apoB is a carrier for LDL, so lower levels mean that less LDL is being carried in the bloodstream.)
"A 12-millimeter of mercury decrease in systolic blood pressure for 10 years has been estimated to prevent one death for every 11 patients with stage one hypertension treated; therefore, the average reduction of 9.9 milligrams of mercury in systolic blood pressure in hypertensive women in the present study could have significant implications for reducing cardiovascular risk and death on a population basis," wrote Welty.
Triglyceride levels also dropped in all the women when eating soy nuts, 7% in those with normal and 11% in those with high blood pressure. (High triglycerides, a form in which fat is carried in the bloodstream, are another cardiovascular disease risk factor.)
"Although these reductions were not statistically significant, their magnitude is similar to reductions in triglyceride levels observed in other soy studies and may have clinical relevance, especially since triglyceride levels are stronger predictors of cardiovascular risk in women than in men," noted Welty.
The researchers speculate that soy isoflavones work synergistically with other compounds in soy nuts, which are roasted whole soy beans, to produce the blood pressure lowering effects. In other studies, in which isoflavones were given in isolation in the form of supplements, no such benefits were observed.
"This study was performed in the free-living state; therefore, dietary soy may be a practical, safe and inexpensive modality to reduce 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," concluded the researchers.
In a similar 16-week diet crossover study, this one looking at menopausal symptoms, Welty's team again gave 60 healthy postmenopausal women two 8-week diets, the TLC diet and a TLC diet with similar calorie, fat, and protein content in which one-half cup soy nuts divided into three or four portions spaced throughout the day (containing 25 g soy protein and 101 mg isoflavones) replaced 25 grms of non-soy protein.(Welty FK, Lee KS, et al, J Women's Health).
Once again, compared with the TLC diet alone, women did much better on the TLC diet with soy nuts. While eating soy nuts, hot flashes dropped 45% in women beginning the study with at an average of at least 4.5 hot flashes a day, and 41% in those who began the study with an average of less than 4.5 hot flashes daily.
Eating soy nuts also resulted in significant improvements in the women's scores on the menopausal symptom quality of life questionnaire: a 19% average decrease in vasomotor symptoms score, 12.9% reduction in psychosocial symptoms score, 9.7% decrease in physical symptoms score, and a 17.7% reduction in sexual symptoms score.