Nattokinase is a fibrinolytic enzyme that comes from natto. Fibrinolytic supplements support the health of the heart and circulatory system by promoting healthy blood flow. A popular Japanese food, natto is made from soybeans fermented with Bacillus natto. The specific fermentation process to make natto is the only way to get nattokinase. Swanson Ultra features a line of nattokinase supplements that deliver different strength amounts of fibrinolytic units.