The Effect of Food Sources of Soy Protein on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

RATIONALE: Hypertension is one of the leading risk factors for death and significantly increases the risk for cardiovascular disease (CVD), brain and kidney diseases. It is also one of the leading modifiable risk factors for CVD. Dietary guidelines for blood pressure management and hypertension emphasize fruits and vegetables, plant-based proteins and foods low in saturated fat. With the growing interest in plant-based alternatives and plant-based diets, there is a need to clarify their benefits on blood pressure. Soy protein is a complete protein and is the only plant-based beverage alternative that is comparable to dairy milk. There are mixed findings on the effects of soy on blood pressure due to differences in study design and subjects. To better address this question and inform public health guidelines the investigators will conduct a systematic review and meta-analysis of randomized controlled trials of the effect of soy protein on reducing blood pressure in individuals with and without hypertension.

OBJECTIVES: To conduct a systematic review of the effect of soy protein by food source on systolic (SBP) and diastolic (DBP) blood pressure in individuals with and without hypertension and assess the certainty of the evidence using the Grading of Recommendations Assessment Development and Evaluation (GRADE) system.

DESIGN: The systematic review and meta-analyses will be conducted according to the Cochrane Handbook for Systematic Reviews of Interventions and reported according to the Preferred Reporting items for Systematic Reviews and Meta-Analyses (PRISMA).

DATA SOURCES: Medline, Embase, and The Cochrane Central Register of Controlled Trials (Clinical Trials; CENTRAL) will be searched using appropriate search terms supplemented by manual searches of references of included studies.

STUDY SELECTION: Randomized controlled trials of ≥3-weeks assessing the effect of soy protein food sources compared with a suitable non-soy-containing control group on blood pressure will be included.