The US Food and Drug Administration approved a health claim for soyfoods and coronary heart disease in 1999 based on the cholesterol lowering effects of soy protein. Since that time numerous meta-analysis have supported the FDA’s decision. The latest one to do so is the largest conducted thus far as it included 35 controlled clinical trials and involved over 3,000 participants. Treatment duration ranged from 4 weeks to 1 year. When all soy products and all subjects were included in the analysis, soy products statistically significantly lowered LDL-cholesterol by 4.83% and lowered triglycerides by 4.92%. There was also a significant increase in serum HDL-cholesterol concentration of 1.40%. Sub-analysis of the data revealed several interesting findings. For example, in people who were diabetic, hypertensive or hypercholesterolemic, soy lowered LDL-cholesterol by 7.47%, which was more than twice the 2.96% reduction in healthy subjects. The meta-analysis also addressed the erroneous claim that soy protein only reduces cholesterol in clinical trials because the control protein consists of casein, which raises cholesterol. However, the meta-analysis found that LDL-cholesterol was actually reduced more in trials in which the control protein was neither casein nor milk protein.
Tokede et al. Soya products and serum lipids: a meta-analysis of randomised controlled trials. Br J Nutr.1-13 (2015).