Nattokinase seems to have some anti-inflammatory and antioxidant effects that can contribute to cardioprotection,[1] but its claim to fame is its ability to reduce blood clotting. Nattokinase seems to reduce blood clotting by breaking down fibrin (a molecule that entangles platelets and creates blood clots) by degrading plasminogen activator inhibitor-1 (PAI-1, a protein that makes clotting more efficient). PAI-1 disables plasminogen activators (PAs), including tissue-type plasminogen activator (tPA), a serine protease which is administered therapeutically to break up blood clots in conditions such as ischemic stroke and heart attack.[1][2] Studies in humans have shown that ingesting a single dose of nattokinase increases blood levels of tPA for about 3 hours,[3] while regular administration (taking 1,300 mg of nattokinase 3 times daily for 8 days) seems to gradually increase tPA in the blood over time.[4] Small studies conducted in generally healthy people, as well as people on dialysis and with cardiovascular disease, showed that taking 800 mg (4,000 fibrinolytic units) of enteric-coated nattokinase 30 minutes after dinner every day for 2 months reduced serum fibrinogen by 7–10%, factor VII by 7–14%, and factor VIII by 17–19% compared to baseline. The reduction in fibrinogen in people with cardiovascular disease and the reduction in factor VII in people on dialysis did not reach statistical significance, possibly due to insufficient power in the study.[5]