Effect of Soy Protein on Blood Pressure in Prehypertensive/Stage 1 Hypertensive Adults

Abstract

Research is mixed on the BP lowering effect of soy protein. However, even if such effects are modest, reductions in hypertension‐related mortality and morbidity in the population could be significant. Thus, the aims were to determine if daily intake of soy milk made from whole soy beans (WSB) or soy protein isolate (SPI) for 8 weeks reduces BP compared to cow's milk (CM) and if the nature of soymilk, WSB (Silk) or SPI (8th Continent) has a bearing on the degree of effect in pre‐/Stage I hypertensives. Participants (n=68) consumed the randomly assigned beverage equal to 21 g of protein/d in this single‐blind study. BP was measured in‐house using the recommended office assessment and with a 24‐hr ambulatory BP monitor at baseline, 4 and 8 weeks. Data analysis shows that while baseline BP did not differ across groups, responses to treatment differed based on the method used to assess BP. In‐house data showed significant improvements in systolic BP (SBP) for all groups and in diastolic BP (DBP) for only the CM group. Ambulatory data showed a significant improvement in DBP for only the CM group. Ambulatory BP likely provides more insight about overall BP because 1) measures are taken every 15 min for 24 h and 2) it also overcomes “whitecoat syndrome” (inflation of BP due to testing environment). Overall, soy protein did not have a greater effect in lowering BP compared to milk protein, and no difference between WSB and SPI was noted.