A result of a study conducted on healthy men at Tokyo Medical University in 2019 showed that Nattokinase was confirmed to increase NK cells (natural killer cells) when 4,000 FU, twice the required intake, was ingested. This has been appeared to have the effect of boosting immunity, in addition to the previously confirmed functionalities such as reducing blood pressure and improving blood flow.
*Citation: Yuko Kurosawa et al. Japanese Pharmacology and Therapeutics Vol.47, no.9: 1463-1469 (2019)