Doctor's Best Nattokinase with an orange cap and a blue-and-white label. The label indicates it contains 2,000 FUs (fibrinolytic units) and 90 veggie capsules.General InformationNattokinase is an enzyme extracted from natto, a traditional Japanese food made from fermented soybeans. It is generally used as a dietary supplement that appears to support circulatory and cardiovascular health.People commonly explore nattokinase when looking into wellness goals such as:Supporting healthy blood flow and circulationMaintaining normal cardiovascular functionAdding a complementary enzyme to a daily heart-health