Context: Nattokinase is a serine protease and is derived from natto, a traditional Japanese, fermented, soybean food meal. Multiple authors have described the significant fibrinolytic, antithrombotic, and antihypertensive effects of natto. Nattokinase has been growing in popularity for use as a dietary supplement for the benefit of cardiovascular health. Little is known regarding the pharmacokinetic and pharmacodynamic properties of this enzyme, and the bioavailability of nattokinase is currently unknown.
Objective: This study intended to (1) detect nattokinase directly and immunologically, (2) show that nattokinase and/or its metabolites were detectable in human blood following ingestion of a commercial preparation, and (3) chart a pharmacokinetic dosing effect for nattokinase.
Design: The research team designed the pilot study as an in vivo, human clinical trial. Healthy human subjects responded to an advertisement and were screened. Subjects who satisfied both inclusion and exclusion criteria were enrolled into the study. Subjects were then instructed to orally ingest a single capsule containing a known concentration of nattokinase immediately following a baseline blood draw. Subsequent blood draws occurred over a 24-h period.
Setting: This study was conducted in Oakland, California, at a clinical reference laboratory and was performed with the approval of an institutional review board (IRB) to ensure that appropriate ethical standards were met.
Participants: Eleven healthy participants (five male, six female, ages 21-65), who met eligibility criteria, were enrolled.
Intervention(s): Administration of nattokinase occurred orally with the ingestion of a single daily dose (2000 FU) of nattokinase. Capsules, each containing approximately 100 mg of nattokinase, in softgel form (NSK-SD, Japan Bio Science Laboratory, Osaka, Japan), were used in the study.
Outcome measure(s): Baseline blood samples were collected, and participants were observed swallowing a single capsule of the nattokinase supplement before returning at 2, 4, 8, 12, 24, and 48 h post ingestion for subsequent blood draws. The presence of nattokinase in serum was measured by an enzyme-linked immunosorbent assay (ELISA), using a rabbit, polyclonal, antinattokinase-capture antibody. A pharmacokinetic pattern was observed for nattokinase between baseline and 48 h postdose.
Results: Peak serum levels of nattokinase were observed at approximately 13.3 h ± 2.5 h (mean ± standard error) postdose. Statistically significant increases in binding were detectable from baseline when comparing averaged data at time points t = 2 h-t = 24 h.
Conclusions: These results provided the first evidence that nattokinase can be measured directly in the blood of humans. The results further suggest that a larger, more extensive, pharmacokinetic study of nattokinase is warranted. Additionally, looking for intact enzyme and bioactive nattokinase peptides should be a consideration for future studies investigating the pharmacokinetic profile of nattokinase.