Nattokinase is a fibrinolytic enzyme extracted from a Japanese food called Natto, often called "vegetarian cheese." Natto, which is made from fermented soybeans, is known to many Americans because it was once featured on an TV episode of Iron Chef and has been eaten in Japan for thousands of years. Nattokinase is known to the alternative medicine community because it functions as a clot-buster and blood thinner, something done by expensive tpa when injected into patients after a heart attack. Studies have shown that nattokinase tends to lower blood pressure and dissolve clots in the body, making people wonder whether it can be a substitute for aspirin therapy.

Natto is produced by fermentation. Manufacturers first add the bacterium "Bacillus natto" (Bacillus subtilis natto)to boiled soybeans. The bacterium acts on the soybeans, and the nattokinase enzyme is produced as a byproduct. The Japanese researcher, Doctor Hiroyuki Sumi, who discovered nattokinase tested 173 other substances for their fibrinolytic clot busting properties, but found nattokinase to be the best of all materials he tested. While various forms of soy contain other enzymes, it is only natto that contains the nattokinase enzyme.

Medical studies have confirmed that nattokinase acts much like human plasmin in dissolving existing blood clots by dissolving the fibrin that binds platelets together. It enhances the body's natural ability to fight blood clots in several different ways other than this fact that it resembles plasmin and dissolves fibrin directly. It also increases the body's production of both plasmin, urokinase and other blood clot-dissolving agents. Nattokinase has been shown to lower blood pressure levels, its traditional use in Japan, perhaps because arteries freed of obstructions end up having lower blood pressure. So studies show it aids blood circulation (flow) by assisting in the clearing of circulation. It has also been shown to help prevent the hardening and narrowing of arteries

There are many brands of nattokinase on the market: Jarrow, Doctors Best, NOW Foods. The best nattokinase brand most often preferred is the Allergy Research - Nutricology brand because it was the first nattokinase introduced into the US market, and has a tie with the original researcher. People prefer the oil capsules to hardened crystalline powder capsules. As a dietary supplement, nattokinase can be taken with or without food. Nattokinase supplements are known to have side-effects such that people suffering from severe bleeding and using blood thinning drugs shouldn't take these supplements, unless otherwise suggested by their doctor who might ask you to try it as an aid to lowering blood pressure.