Why were soybean-flour soft drinks marketed in some tropical areas?

In tropical areas, soft drinks containing soybean flour have been marketed primarily to address nutritional deficiencies, as these regional diets frequently lack sufficient protein.1

Soybeans are a valuable food source because they provide protein of high biological value, with an amino acid profile that closely resembles that of animal protein. By incorporating soy flour into beverages, manufacturers sought to provide a more nutritious option in regions where protein intake was often inadequate.21