ST. LOUIS, Aug. 16, 2011 /PRNewswire/ -- A new study found that both soy and low-fat milk protein intake may reduce blood pressure compared with carbohydrate among people with hypertension (high blood pressure). The findings are published in the Aug. 2 edition of Circulation: Journal of the American Heart Association.
"Protein-rich soyfoods have long been seen as heart-healthy additions to the diet and these findings further support this," said Mark Messina, Ph.D., a nutrition expert, adjunct associate professor in the Department of Nutrition, School of Public Health, Loma Linda University, and the executive director of the Soy Nutrition Institute. "This is good news for the 75 million Americans with elevated blood pressure because even a small decrease in blood pressure, as seen in this study, may have important health benefits."
Jiang He, M.D., a professor of epidemiology at the Tulane University School of Public Health and Tropical Medicine in New Orleans, led the randomized, double-blind crossover study. The trial involved three phases among 352 adults with pre-hypertension or stage 1 hypertension from September 2003 to April 2008. Participants were divided into three groups and received 40g daily of either soy protein, low-fat milk protein or carbohydrate supplementation for eight weeks each, with a three-week washout period in between each phase.
The primary goal of the study was to test whether a soy protein or low-fat milk protein supplementation would reduce systolic (the top number in a blood pressure reading) blood pressure compared with a complex carbohydrate. Research indicates that even a small decrease, as seen in this study, could lead to a 6 percent reduction in death from stroke, 4 percent reduction in death from heart disease and 3 percent reduction in deaths from all causes.
Soy and Health
The findings from this study support the idea that replacing carbohydrate with soy protein may reduce blood pressure and the notion that vegetable protein intake can be an important part of the diet for the control of high blood pressure. Additionally, Dr. He and colleagues found that soy protein raised good (HDL) cholesterol in comparison to low-fat milk protein and carbohydrate while also lowering bad (LDL) cholesterol more, although the latter finding was not statistically significant.
A number of other recent analyses have examined the effects of soy on blood pressure. Earlier this year, Chinese and American researchers analyzed the results of 27 different clinical trials dating back to 1997, which included a total of 1,608 subjects, and found that soy lowered systolic blood pressure as well as diastolic (the bottom number in a blood pressure reading) blood pressure. Three other analyses published since 2008 also confirmed the blood pressure-lowering effects of soy protein.
Adding Soy to Your Diet
"Soyfoods can be an important component of a healthy diet and studies like this provide further evidence of the impact what you eat has on your overall health," said nutrition expert Joy Blakeslee, RD. "It's simple to add soy into your diet with foods like tofu, soymilk, edamame and soynuts."
The amount of soy protein shown to potentially lower cholesterol is about 25g daily, while the amount needed to lower blood pressure has not been firmly established. In this study, subjects consumed 40g daily, but other studies have suggested lower amounts of soy protein may also be effective in lowering blood pressure.
According to Blakeslee, you can get 25g of soy by adding one ounce of soynuts to trail mix, enjoying a soymilk latte in the afternoon and adding a half of a cup of edamame to your dinner salad. You could also try stir-frying one serving of tofu with vegetables, making a breakfast smoothie with berries and one cup of soymilk and having a half of a cup of edamame as a snack.
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