Also known as: Natto extract, Subtilisin NAT, NSK-SD, Fibrinolytic enzyme
FoundationalEmerging evidence
An enzyme isolated from natto, the Japanese fermented soybean food, studied for its fibrinolytic activity. Measured in fibrinolytic units rather than milligrams, and carries a meaningful interaction profile with blood-thinning medication.
Typical dose
2000.0–4000.0 FU per day
On an empty stomach, commonly before bed
What it is
Nattokinase is a protein-digesting enzyme produced by bacteria during fermentation of soybeans into natto, a traditional Japanese breakfast food with a distinctive smell and stringy texture. It was identified in the 1980s during research into the clot-dissolving properties of the food.
Potency is expressed in fibrinolytic units, abbreviated FU, rather than in milligrams of material. A common serving is 2,000 FU. Because enzyme activity rather than mass determines effect, a milligram figure on a label without an FU figure tells you very little.
Quality preparations are purified to remove vitamin K2, which natto contains in large amounts and which affects clotting in the opposite direction. That purification is worth checking on any product.
How it works
Nattokinase degrades fibrin, the protein mesh that gives blood clots their structure. It acts directly on fibrin and also appears to enhance the body's own fibrinolytic system by influencing plasminogen activator activity and reducing plasminogen activator inhibitor-1.
An unusual feature is that this enzyme appears to survive digestion sufficiently to have systemic effect, which is not typical for orally administered proteins. Enteric coating is used to protect it from stomach acid, and the extent of intact absorption remains debated.
Effects on blood pressure have also been reported, attributed to inhibition of angiotensin-converting enzyme activity, a mechanism distinct from the fibrinolytic action.
What the evidence shows
Human trials exist but are generally small and a substantial share originate from Japanese research groups with industry involvement. Several have reported reductions in fibrinogen, factor VII and factor VIII, and some have reported modest blood pressure reductions.
Work on arterial plaque and on markers of blood viscosity has produced some encouraging findings, though sample sizes are modest and independent replication is limited.
What has not been demonstrated is that any of this translates into reduced cardiovascular events. Biomarker change is not outcome change, and this ingredient is frequently marketed as though that gap did not exist. Anyone considering it for a cardiovascular reason should be making that decision with a doctor, not a supplement label.
Dosing
Standard serving is 2,000 FU daily, with some protocols using up to 4,000 FU. Trials have most often used 2,000 FU.
Dose by fibrinolytic units, not milligrams. A product listing only a milligram figure gives you no way to judge potency, and this is the single most common labelling shortcoming in the category.
Usually taken on an empty stomach, either before bed or between meals, and enteric-coated preparations are preferred to protect enzyme activity through the stomach. Effects on coagulation markers in trials appear over weeks of consistent use.
Fibrinolytic activity reported over several hours following a dose
Timing
On an empty stomach, commonly before bed
Competition status
Permitted — not on the WADA Prohibited List
Category
Foundational
Safety and side effects
Generally well tolerated in the trials conducted, with mild digestive upset the most commonly reported effect. Natto itself has been eaten in Japan for centuries, offering some reassurance about the source material.
Bleeding risk is the serious consideration and should not be understated. Because nattokinase acts on how clots are broken down, combining it with medication that thins the blood or reduces clotting could meaningfully increase the risk of bleeding, and there are documented reports of bleeding events associated with its use.
It should be stopped well in advance of any surgery or dental procedure. Anyone who bruises or bleeds unusually easily should avoid it.
Who should avoid it
Do not use alongside any medication that thins the blood or affects clotting without medical supervision. Avoid if you bruise or bleed unusually easily, or have recently had surgery. Stop at least two weeks before any surgical or dental procedure. Avoid in pregnancy and breastfeeding. Speak to your doctor before use if you take regular medication. Soy-derived: relevant for allergen declaration.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
