We Brought Nattokinase to America in 2001 — and Most of What Sells as “Nattokinase” Today Isn’t Even Real

I’m going to tell you what happened to nattokinase between then and now — because what happened is not a story about a good ingredient finally getting the attention it deserves. It’s a story about a good ingredient getting counterfeited at scale. By the mid-2010s, the shelves were full of products labeled “Nattokinase” that, when independently tested, contained no nattokinase at all. Many weren’t even derived from natto. Almost none had ever been near a clinical trial. And the vast majority were not produced by the Japanese fermentation process that gave the enzyme its name and its forty years of research.

I’m not going to name the brands — I’ll let the testing data do that work. But I am going to tell you exactly how to separate the real thing from the fakes, and I’m going to put the two strains I actually trust — including the one Dr. Hiroyuki Sumi, the enzyme’s discoverer, endorses exclusively — at the front of this conversation.

The story starts with Dr. Hiroyuki Sumi, a Japanese biochemist who was studying fibrinolytic enzymes — compounds capable of dissolving fibrin, the protein that forms the mesh of a blood clot. In 1980, working at the University of Chicago, he dropped a small piece of natto, the traditional Japanese fermented soybean food, onto a fibrin plate in a petri dish. Within eighteen hours the fibrin had dissolved in a perfect circle around the natto. He’d found an enzyme with remarkable clot-dissolving activity. He named it nattokinase.1

Nattokinase is produced by Bacillus subtilis var. natto — the specific subspecies used to ferment traditional natto for centuries in Japan. It is a serine protease that cleaves fibrin directly, activates the body’s own tissue plasminogen activator (tPA), and inhibits PAI-1, the compound that blocks fibrinolysis. It also appears to inhibit ACE, the same enzyme targeted by a major class of blood pressure medications2. Four decades of research — more than seventeen human clinical trials — sit behind it3. That is the enzyme. That is what the word “nattokinase” is supposed to mean.

For two decades before 2001, if you wanted nattokinase in this country, you mostly needed a doctor willing to stock it. As a practitioner, I’d seen it in physicians’ offices and alternative pharmacies — but mainly at trade shows and conferences, where professional-grade nutrition products surfaced long before they reached the consumer. Pure Prescriptions changed that. We were the first company in the United States to bring a professional-grade nattokinase direct to consumers — because I believed professional-grade nutrition shouldn’t require a referral.

By 2002 we’d put it under our own label and named it Cardiokinase®, formulated with a patented strain developed by Dr. Sumi himself, manufactured in Japan and imported directly. In 2008, Dr. Sumi developed an even more potent strain — HTNK-J® — and brought it to us exclusively. The following year, the Nutrition Business Journal recognized Cardiokinase® with a Product Merit Award. That’s the origin. Now here’s what happened to the category we opened up.

Through the 2010s, nattokinase started getting real attention outside Japan — first in Taiwan, then across the US supplement market. Demand outran supply almost overnight. And the supply that rushed in to meet that demand was, in many cases, not the supply that had built the research.

Here is the problem in plain terms. Real nattokinase comes from a specific fermentation: soybeans cultured with Bacillus subtilis var. natto — the strain used to make traditional Japanese natto for centuries. It is not a generic enzyme you can crank out of any bacterium. But as the category grew, manufacturers began producing “nattokinase” from other Bacillus subtilis strains and from entirely different fermentation substrates, then selling the resulting enzyme under the same name. The molecule is different. The activity is different. The safety profile is different. And the clinical research — all of which was conducted on authentic nattokinase from Bacillus subtilis var. natto — does not apply to it.

“When they tested the raw material coming out of the US, it didn’t just have less nattokinase. It had none. Different enzyme, same label.”

This is the part the marketing copy never mentions. The human trials — the blood pressure reductions, the fibrinogen lowering, the carotid plaque regression data that made nattokinase famous — were all conducted on authentic nattokinase standardized to a verified FU value. If your “nattokinase” was fermented from a different bacterium on a different substrate and shows a different degradation pattern under HPLC, those studies do not describe what is in your bottle. You are taking an untested enzyme and borrowing the credibility of a tested one.

That’s not a reformulation. That’s a bait and switch. And it’s the reason a category I helped build now has a trust problem it didn’t have to have.

After twenty-five years, there are exactly two nattokinase raw materials I will put my name behind. Both are legitimate. Both are real nattokinase from authentic Bacillus subtilis var. natto fermentation. They are not the same, and the difference matters.

“There are two real nattokinases on the market. One built the research. The other was built by the man who discovered the enzyme. Everything else is a label.”

You don’t need a chemistry lab to protect yourself. You need to know what to look for on a label — and what to walk away from.

Look for the strain name. “Nattokinase” alone on a label, with no strain specified, is a red flag. Legitimate products name the strain — NSK-SD® or HTNK-J®. If a manufacturer has a real strain, they want you to know which one.

Look for the FU value, not just milligrams. The JNKA standard daily dose is 2,000 FU4. A bottle that lists only milligrams with no FU specification tells you nothing about potency. Two products can both claim 100mg and have a tenfold difference in actual fibrinolytic activity.

Look for proof of origin — a disclosed Japanese manufacturer, JNKA membership, or the JNKA mark. Look for third-party testing and a Certificate of Analysis you can actually request. And if the price looks too good to be true, it is. Authentic nattokinase cannot be fermented, shipped from Japan, third-party tested, and sold at the bottom of the price range. The cheap bottles are cheap because the enzyme inside them isn’t the enzyme on the label.

Nattokinase’s popularity spiked hard in 2022 and 2023 — driven by cardiovascular interest and a broader conversation about circulatory health. When demand spikes that fast, counterfeits rush in to fill the gap. The exact same thing happened in Taiwan in 2010, when the JNKA held a public press conference to promote the eradication of counterfeit nattokinase products. The pattern is repeating now in the US, and most consumers have no idea it’s happening.

If you’re taking nattokinase for your cardiovascular health, you deserve to know whether you’re actually taking nattokinase. The category we opened in 2001 has become one of the most counterfeited in the supplement aisle. The way to not get fooled is to buy from the people who were there at the beginning — or, at minimum, from a strain that has been tested and named. Cardiokinase® with HTNK-J® is the one I trust with my name on it. NSK-SD® is the one I trust with Dr. Sumi’s research behind it. Almost everything else on the shelf is a guess.

We were there at the beginning of this category. Twenty-five years later, we’re still one of the only companies that can tell you — down to the strain, the facility, and the discoverer’s endorsement — exactly what’s in the bottle. That’s the standard nattokinase should be held to. Hold the bottle in your hand to that standard, and most of the aisle disappears.