Chinese Buddhist missionaries brought it to Japan where it was first enjoyed primarily by the upper classes. The first Western soy foods were actually invented by a champion of breakfast cereals. John Harvey Kellogg, inventor of foods like granola, wrote extensively about the health benefits of soy foods in 1919. He invented and championed the first Western soy milk in 1920. Nutrient content of soy milk varies widely by brand.
Some brands are low in protein.
Meta-analysis of effects of soy protein intake on serum lipids in humans. Relationship of animal protein-rich diet to kidney stone formation and calcium metabolism. Kontessis P, Jones SL, Dodds R, et al. Renal, metabolic and hormonal responses to ingestion of animal and vegetable proteins. McMicheal-Phillips EF, Harding C, Morton M, Roberts ST et al.