Nattokinase: Enzyme Activity, FU Potency & Human Research

This page is part of the AMLApure Nattokinase Science & Education hub and the AMLApure Ingredient Science Library. It is intended for holistic, integrative, and nutrition-focused healthcare professionals and scientifically interested consumers. This content is educational in nature and does not constitute medical advice.

What Is Nattokinase?

Nattokinase is a serine protease enzyme associated with Bacillus subtilis var. natto — the bacterium responsible for fermenting soybeans into natto, the traditional Japanese food. The enzyme was first isolated and characterized in 1987 by Dr. Hiroyuki Sumi, who identified fibrinolytic activity in the natto preparation.

Nattokinase preparations are not the same as eating natto. Commercial nattokinase is an extracted, purified, and standardized enzyme preparation derived from the fermentation process. It is produced under controlled manufacturing conditions and tested for enzyme activity — not simply dried or powdered natto. Eating natto provides a complex whole-food profile including Vitamin K2, dietary fiber, and other fermented food compounds; a nattokinase supplement provides a concentrated, standardized fibrinolytic enzyme preparation, typically manufactured to be Vitamin K2-free.

For a detailed account of the distinction, see Nattokinase vs Natto: What’s the Difference?

How Nattokinase Is Produced

Commercial nattokinase is produced through controlled fermentation of Bacillus subtilis var. natto. The fermentation process generates the enzyme, which is subsequently extracted, purified, and concentrated from the fermented material.

After extraction, the enzyme preparation is processed, standardized to an activity specification, tested for identity and purity, and typically tested for Vitamin K2 removal — an important consideration for individuals who may be sensitive to Vitamin K2’s effects on coagulation.

For a more detailed explanation of the manufacturing process, see How Is Nattokinase Made? Fermentation Explained.

What Does FU Mean?

FU stands for Fibrinolytic Units — a measure of fibrinolytic enzyme activity determined under specified assay conditions. FU is the standard unit used to express nattokinase enzyme potency in nutritional formulations.

Understanding FU is important because:

  • FU measures what the enzyme does — its capacity to catalyze the breakdown of fibrin under the assay conditions
  • Milligrams measure weight only — they do not measure enzymatic activity
  • Two nattokinase preparations with identical milligram weights can have meaningfully different FU values depending on the enzyme’s activity concentration

The FU measurement is generated using a standardized fibrinolytic assay. Results are expressed per gram of ingredient or per serving, depending on context.

For a thorough explanation, see What Does FU Mean in Nattokinase? — part of the Nattokinase Science & Education hub.

Milligrams vs Enzyme Activity

This distinction matters practically when comparing products. Two nattokinase supplements may both list “200 mg nattokinase” on their labels but deliver substantially different enzyme activity depending on the FU concentration of their respective ingredients.

Milligrams = weight of the ingredient.
FU = measured enzyme activity under specified assay conditions.

These are not interchangeable. A higher milligram amount does not automatically mean higher enzyme activity. A lower milligram amount from a highly concentrated ingredient may deliver more FU than a larger milligram dose from a less concentrated preparation.

Important: Higher FU does not automatically predict a superior clinical outcome. FU measures analytical enzyme activity in a standardized assay — not a clinical result in a human body.

The Nattokinase Science & Education hub provides further resources, including What Does FU Mean in Nattokinase? and How Is Nattokinase Potency Tested?

Nattokinase, Circulation & Fibrin Research

Nattokinase has been the subject of scientific research primarily focused on its fibrinolytic properties — specifically its capacity to act on fibrin, a structural protein involved in the normal clotting process.

Fibrin in normal physiology: The body continuously produces and breaks down fibrin as part of normal hemostatic balance. Maintaining healthy fibrin metabolism is part of normal circulatory function. Research has examined whether nattokinase enzyme activity in laboratory settings corresponds to effects on fibrin-related markers in humans.

Types of evidence — clearly distinguished:

In vitro (laboratory): Nattokinase has demonstrated fibrinolytic activity in numerous laboratory assays. These findings establish that the enzyme can act on fibrin-related substrates under controlled conditions. Laboratory findings do not automatically translate to equivalent effects in humans.

Animal research: Animal model studies have examined nattokinase in contexts involving blood viscosity and circulation-related markers. Animal findings are not directly applicable to human physiology without supportive human clinical evidence.

Human research: A body of human research exists, including pilot studies and some randomized controlled trials examining nattokinase in the context of circulation-related biomarkers, blood viscosity, and cardiovascular wellness indicators. See the section below for a balanced summary.

Nothing on this page constitutes a claim that nattokinase treats, prevents, cures, or dissolves blood clots, thrombosis, stroke, heart attack, hypertension, or any cardiovascular disease.

What Human Research on Nattokinase Shows

The human research base for nattokinase is more developed than for many dietary enzyme ingredients, though important limitations apply.

Areas with published human research:

  • Blood viscosity and hemorheology: Several small human studies have examined nattokinase in the context of blood viscosity markers. Results have generally been preliminary, with modest sample sizes.
  • Fibrin-related biomarkers: Human pilot studies have measured changes in fibrinogen and related markers following nattokinase supplementation. Findings are mixed and study designs vary substantially.
  • Cardiovascular wellness indicators: Some randomized controlled trials have examined nattokinase alongside lipid and blood pressure markers. One published RCT (Kim et al., 2008, Hypertension Research) examined nattokinase supplementation in a human cohort and reported changes in blood pressure markers over 8 weeks. This study used a specific nattokinase preparation and dose that may not be equivalent to all commercial products.
  • Combination studies: Some human research involves nattokinase in multi-ingredient formulations, making it difficult to isolate the contribution of nattokinase alone.

Limitations of the evidence base:

  • Most human studies have small sample sizes and limited follow-up durations
  • Study preparations and FU doses vary considerably, limiting cross-study comparisons
  • Many findings are preliminary and require replication in larger, well-controlled trials
  • Research on specific commercial preparations does not automatically apply to all nattokinase ingredients

No statements on this page should be interpreted as claims that nattokinase or AMLApure products diagnose, treat, cure, or prevent any disease.

For broader research context, see the Research & Testing Library and Nattokinase Science & Education.
External resource: PubMed — nattokinase human clinical research

Understanding FU Potencies in Formulations

AMLApure offers nattokinase formulations across a range of FU levels to support different wellness contexts and personal preferences:

Browse all formulations: Nattokinase — AMLApure Science Hub collection

Higher FU does not automatically mean clinically better outcomes. The appropriate FU level for an individual’s wellness routine is a personal decision best made in consultation with a qualified healthcare professional, particularly for those with health conditions or taking medications.

Multi-Ingredient Formulations

Nattokinase is frequently formulated alongside other botanical ingredients. AMLApure’s approach combines nattokinase with complementary plant-derived compounds that contribute distinct nutritional profiles.

AMLA (Indian Gooseberry): Several AMLApure formulations combine nattokinase with Organic AMLA — a whole-food botanical that provides naturally occurring Vitamin C and a range of polyphenols including emblicanins, gallic acid, and ellagic acid. For the phytochemistry behind this ingredient, see amla fruit and polyphenol science — Amla Ingredient Science Library.

Bergamot: AMLApure’s Nattokinase 4K + Bergamot formula adds Citrus bergamia polyphenols — a botanical studied in the context of lipid and metabolic wellness.

Quercetin, Bromelain, and Vitamin C: The Enterinex™ range combines nattokinase with multiple enzyme and antioxidant botanicals for a broader multi-ingredient approach. For the science behind quercetin, see Sophora japonica and quercetin science — Ingredient Science Library.

Omega-3 (DHA & EPA): AMLApure’s Omega-3 tincture pairs algae-derived DHA and EPA with amla extract. For botanical and fatty acid formulation science, see AMLA and omega-3 DHA and EPA formulation science.

This page is part of the AMLApure Ingredient Science Library. Content is educational and does not constitute medical advice. These statements have not been evaluated by the FDA. AMLApure products are not intended to diagnose, treat, cure, or prevent any disease.