Doctor's Best Nattokinase helps support cardiovascular and circulatory health. Nattokinase is an enzyme derived from natto, a traditional Japanese food made from soybeans fermented with a type of bacteria. Nutritionists and researchers have found that Nattokinase can make a significant impact in supporting our circulation and cardiovascular health at any age.* Natto is produced by a fermentation adding the bacteria Bacillus subtilis to boiled soybeans. The resulting Nattokinase enzyme is produced when Bacillus subtilis acts on the soybeans. While other soy foods contain enzymes, it is only the natto preparation that contains the specific Nattokinase enzyme.