VANCOUVER, B.C. — Increased intake of soybean protein may provide an important means of preventing and treating hypertension, Jiang He, M.D., declared at a meeting sponsored by the International Academy of Cardiology.
He presented results from a multicenter, double-blind, randomized, controlled trial of soybean protein in 302 Chinese adults with prehypertension or stage 1 hypertension. Participants in the 12-week trial ate cookies containing either 40 g/day of isolated soybean protein or 40 g of complex carbohydrates from wheat. The cookies were identical in taste and appearance. Most subjects ate them in lieu of their usual breakfast. Adherence was excellent, with 93% of all cookies in both groups being eaten.
Baseline mean blood pressure was 135.0/84.7 mm Hg.
The main study finding was a highly significant net blood pressure reduction of 4.3 mm Hg for systolic and 2.8 mm Hg for diastolic in the soy arm, compared with the control group.
This effect was larger than was found in studies of currently recommended lifestyle modifications, with the single notable exception of the National Heart, Lung, and Blood Institute-sponsored Dietary Approaches to Stop Hypertension (DASH) diet, noted Dr. He of Tulane University, New Orleans.
The blood pressure reduction was greater in subjects with stage 1 hypertension than in those who were prehypertensive. Indeed, stage 1 hypertensives experienced a net reduction of 7.9/5.3 mm Hg in response to soybean protein supplementation. The 2.4/1.3-mm Hg reduction in prehypertensive subjects didn't achieve statistical significance; however, the study wasn't powered for subgroup analysis, according to the physician.
It's worth noting that soybean protein has ancillary health benefits, Dr. He added. It has been shown in randomized controlled trials to significantly reduce serum LDL, total cholesterol, and triglycerides.
Session cochair Martha L. Daviglus, M.D., of Northwestern University, Chicago, noted that the observational International Study on Macronutrients and Blood Pressure, in which she was an investigator, found an association between greater consumption of vegetable protein—but not animal protein—and lower blood pressure. This raises the question of whether the blood pressure-lowering effect documented in Dr. He's study is unique to soy protein or might be achievable with a diet enriched with mixed vegetable protein.
The daily portion of soy cookies contained 76 mg of total isoflavones, including 45 mg of genistein and 27 mg of daidzein.
The study was funded by Tulane University; the National Heart, Lung, and Blood Institute; and the Ministry of Science and Technology of the People's Republic of China.