Does nattokinase work against blood clots and for your heart?

Nattokinase is an enzyme derived from natto, a Japanese fermented soy product, and has been shown to be active on the coagulation system in laboratory and early clinical research. In a small double-blind, placebo-controlled study of 12 healthy men, several coagulation and fibrinolysis parameters changed measurably within 2 to 8 hours after a single dose. All values remained within normal limits, however, so there was no clinical danger for these healthy participants.

An open-label study in 45 people without a placebo group showed a decrease in three coagulation factors in the blood after two months of daily use: fibrinogen fell by 7 to 10 percent, and other coagulation factors declined by 7 to 14 percent and 17 to 19 percent respectively. Because there was no control group, the role of other factors cannot be ruled out. In a test-tube study, nattokinase reduced the clumping of red blood cells and the viscosity of blood in a dose-dependent manner, but whether this also occurs in the human body has not been demonstrated.

On the question of whether nattokinase also counters arterial calcification, the largest available study gives a clearly negative answer. A double-blind, placebo-controlled study in 265 participants over an average of three years found no measurable effect whatsoever on arterial calcification, blood pressure, or blood markers in healthy people with low cardiovascular risk. This is the best evidence available to date, and it contradicts the more optimistic results of smaller studies.

A randomised study in 76 participants compared nattokinase with a cholesterol-lowering drug (statin) and found that arterial plaque in the carotid artery decreased by 36.6 percent in the nattokinase group, compared with 11.5 percent in the statin group. Caution is warranted: the study was small, conducted exclusively in China, and the mechanism is unclear. LDL cholesterol fell less strongly than with statins. This finding has not yet been confirmed by larger studies.

Nattokinase is not a registered medicine. Large clinical safety studies of the kind that exist for modern blood thinners do not exist for it. Anyone who uses blood thinners or other heart medications would be wise to discuss this with their doctor before adding nattokinase to their daily routine, due to possible interactions.