Nattokinase 50 mg, 60 Softgels, Source NaturalsNattokinase Systemic Enzyme For Healthy Circulation. Nattokinase is a systemic enzyme isolated from the traditional Japanese soy food natto. It has been shown to support healthy blood flow by assisting in the circulatory clearing system of the body. Supplement Facts for 50 mg Softgels Serving Size: 2 Softgels Amount %DV Nattokinase (NSK SD) 100 mg providing 2,000 fibrin units (FU) of activity Other Ingredients: rice bran oil, gelatin, purified water,