Nattokinase: The Fermented-Soy Enzyme Your Arteries Keep Asking About

The Oasis Health Journal · Submitted July 4, 2026 · 11:17 AM ET

Natto is a breakfast food that looks like it lost a fight. Fermented soybeans, sticky strings, a smell that can clear a room. Somewhere in that mess lives an enzyme called nattokinase, and the heart-health corner of the internet will not stop talking about it.

Here is the origin story. In 1987 a Japanese researcher named Hiroyuki Sumi tested more than 170 foods to see if any could dissolve a blood clot. He dropped natto onto a lab-made fibrin clot, went home, and came back to find the clot had melted away. That is a strange way to find a cardiovascular supplement. Then again, most good things get discovered by someone poking at their lunch.

Quick anatomy. Fibrin is the stringy mesh your body weaves to build a clot. Great when you are bleeding, less great when it piles up somewhere it should not. Nattokinase is a fibrinolytic enzyme, which is a five-syllable way of saying it cuts fibrin apart. In a test tube it does this about four times better than plasmin, the enzyme your own body keeps on staff for the same job. It also jams a molecule called PAI-1, which is basically the brake pedal on your natural clot-cleanup system. Nattokinase finds the brake and lifts its foot off.

That is the mechanism, and mechanisms sound amazing right up until you remember most of them happen in glassware. A dish is not a person. So here is what actually shows up in humans, good news first.

Blood pressure has the tidiest evidence. In a 2008 randomized controlled trial, 86 adults with creeping blood pressure took 2,000 FU of nattokinase daily for eight weeks. Systolic pressure fell about 5.5 points more than placebo, diastolic about 2.8. Not a fireworks show. Roughly what you get from losing a few pounds or easing off the salt. But it was placebo-controlled and it held up in a later North American trial, so the effect looks real if modest.

Then it gets messier, which is the honest part. A 2022 study followed 1,062 older adults taking a hefty 10,800 FU a day for a full year. Their LDL and triglycerides dropped, their HDL climbed about 16 percent, and the plaque in their carotid arteries measurably shrank. Great numbers. The asterisk: it was retrospective, meaning researchers looked backward at people who were already taking it, with no placebo group holding the other door. That design flatters a supplement the way good lighting flatters a dating profile.

For the counterweight, a 2021 randomized controlled trial (the kind with a real placebo group) gave nattokinase to healthy, low-risk adults for a median of three years and found basically nothing happened to their artery plaque. So the clean story of nattokinase scrubbing arteries spotless is not settled. The blood-pressure and blood-thinning effects are reasonably supported. The plaque-reversal claim is still arguing with itself in the journals.

Dose is its own rabbit hole. Nattokinase is measured in FU (fibrinolytic units), not milligrams, because it is sold by what it does rather than what it weighs. The big artery study used 10,800 FU and specifically noted that 3,600 FU did nothing. Plenty of shelf products sit at 2,000 FU, which lines up with the blood-pressure data but is a sliver of the artery-study dose. Read the FU on the label, not the pill count. A quality nattokinase prints it plainly, and some formulas pair it with serrapeptase, another enzyme people stack for circulation.

Now the part that is not optional. Nattokinase thins your blood. That is the entire point, and also the entire risk. Memorial Sloan Kettering says it plainly: do not take it if you are on anticoagulants, take daily aspirin, have a clotting disorder, or have a history of deep vein thrombosis. There are real case reports of serious bleeding, including a man who swapped nattokinase for his prescribed warfarin after a heart-valve replacement and landed back in surgery. And natto is naturally loaded with vitamin K, which works directly against warfarin. If you take any blood thinner, or you have surgery on the calendar, this is a talk with your doctor, not a thing you try because a fermented bean impressed a scientist in 1987.

A note on quality, because enzymes are divas. Heat, time, and a stockroom shelf are not their friends, and an enzyme that has degraded is just expensive powder. This is where being fussy earns its keep. We source professional-grade formulas fresh per order instead of letting bottles quietly age in a bin, so the FU on the label has a fighting chance of matching the FU in the capsule. It ships a little slower. Potency that has not been sitting around since last winter is worth the extra day or two. If you are building out a heart shelf, people often set nattokinase beside vitamin K2 and CoQ10 (though if you are on warfarin, vitamin K is another doctor conversation, not a solo decision).

The honest summary: nattokinase is a genuinely interesting enzyme with one well-supported trick, nudging blood pressure and gently thinning blood, and one oversold trick, reversing plaque. Respect the first, stay skeptical of the second, and respect the bleeding risk most of all.

This article is for education only and is not medical advice. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Talk with a qualified healthcare professional before starting nattokinase, particularly if you take blood thinners, have a bleeding disorder, or have surgery scheduled.

Sources

1. Sumi H, et al. A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto. Experientia, 1987.
2. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomarker Insights, 2018.
3. Kim JY, et al. Effects of nattokinase on blood pressure: a randomized, controlled trial. Hypertension Research, 2008.
4. Effective management of atherosclerosis progress and hyperlipidemia with nattokinase: a clinical study with 1,062 participants. Frontiers in Cardiovascular Medicine, 2022.
5. Hodis HN, et al. Nattokinase atherothrombotic prevention study: a randomized controlled trial. Clinical Hemorheology and Microcirculation, 2021.
6. Memorial Sloan Kettering Cancer Center. Nattokinase (About Herbs).