Understanding the Mechanism of Nattokinase
Nattokinase is a serine protease enzyme derived from Bacillus subtilis, the bacterium used to ferment soybeans into the traditional Japanese food, natto. Its primary action is fibrinolytic, meaning it helps to dissolve fibrin, a protein that is crucial for forming blood clots. This property is why nattokinase is sometimes promoted for cardiovascular health, with some studies suggesting it may help prevent blood clots and lower blood pressure. However, this powerful blood-thinning effect is also the source of its most serious contraindications and risks. The lack of FDA regulation for dietary supplements means that safety data is often limited, and users must exercise extreme caution.
Absolute Contraindications: When Not to Take Nattokinase Under Any Circumstances
Taking Anticoagulant or Antiplatelet Medications
This is the most critical contraindication for nattokinase. Taking nattokinase with prescribed blood thinners significantly increases the risk of excessive bleeding and bruising. The combination can have an additive effect, intensifying the blood-thinning process beyond safe levels. Case reports have documented serious complications, such as internal bleeding and even death, in patients who took nattokinase, sometimes in place of prescribed medication like warfarin.
Common medications that interact dangerously with nattokinase include:
- Warfarin (Coumadin): Nattokinase's effects can compound warfarin's action. The fermented soybeans in traditional natto also contain vitamin K, which can interfere with warfarin's efficacy, though many supplements are now vitamin K-free.
- Aspirin: Combined use can increase the risk of bleeding, including potentially severe intracerebral hemorrhage.
- Clopidogrel (Plavix): This antiplatelet drug and nattokinase can increase bleeding risk when taken together.
- Nonsteroidal Anti-inflammatory Drugs (NSAIDs): Medications like ibuprofen and naproxen also have antiplatelet effects, which can be amplified by nattokinase.
Before and After Any Surgical Procedure
Because of its ability to impair blood clotting, nattokinase must be discontinued before and after surgery to prevent excessive bleeding. This includes major and minor procedures, as well as dental surgery. Experts recommend stopping nattokinase at least two weeks prior to a scheduled operation. It is crucial to inform all healthcare providers, including dentists, about all supplements being taken.
History of or Risk for Ischemic Stroke
While some research explores nattokinase as a protective agent, its clot-dissolving properties also carry a theoretical risk. It could cause an existing, stable blood clot to dislodge and travel to the brain or lungs, potentially triggering a life-threatening stroke or embolism. For this reason, those with a history of ischemic stroke, deep vein thrombosis, or cerebral microbleeds should avoid nattokinase.
Medical Conditions and Health Statuses
Individuals with Bleeding Disorders
People with inherited bleeding disorders, such as hemophilia, should never take nattokinase. Their compromised clotting ability would be further worsened by the enzyme's fibrinolytic activity, leading to a high risk of spontaneous and uncontrollable bleeding.
Pregnant or Breastfeeding Individuals
There is a significant lack of reliable research and safety data regarding nattokinase use during pregnancy and lactation. To avoid potential harm to the mother or baby, it is strongly advised to avoid nattokinase supplements during these periods. Sticking to food amounts is generally considered safer, though supplementation should be discussed with a doctor.
Allergies to Soy or Natto
Nattokinase is derived from fermented soybeans, and can trigger allergic reactions in individuals with a soy or natto allergy. Some cases of severe, late-onset anaphylaxis have been reported, often due to an allergy to poly-gamma-glutamic acid (PGA), a component in the viscous mucilage of natto.
Chronically Low Blood Pressure (Hypotension)
Nattokinase may lower blood pressure. For individuals already dealing with hypotension, taking this supplement could cause blood pressure to drop to dangerously low levels, leading to dizziness, fainting, or headaches. People with high blood pressure who are taking antihypertensive medications should also be cautious, as nattokinase could have additive effects.
When Not to Take Nattokinase: Key Scenarios Comparison
| Scenario | Risk Level | Reason | Key Action |
|---|---|---|---|
| Taking Blood Thinners | High | Increases risk of severe bleeding and bruising due to amplified anticoagulant effects. | Absolutely avoid combination. Consult doctor for alternatives. |
| Before Surgery (Medical/Dental) | High | Increases risk of excessive bleeding during and after the procedure. | Stop taking at least 1-2 weeks prior. |
| History of Ischemic Stroke | High | Theoretical risk of dislodging existing clots, causing embolism or another stroke. | Avoid completely unless under strict medical supervision. |
| Bleeding Disorders (e.g., Hemophilia) | High | Worsens already compromised blood clotting, leading to dangerous bleeding. | Never take nattokinase. |
| Pregnancy or Breastfeeding | High | Insufficient safety data, potential unknown risks to mother and baby. | Avoid use; consult with healthcare provider. |
| Soy or Natto Allergy | Moderate-High | Risk of allergic reactions, including potentially severe anaphylaxis. | Avoid if known allergy to natto or soy. |
| Taking Antihypertensives | Moderate | Potential for blood pressure to drop too low, especially in those with hypotension. | Monitor blood pressure closely with medical advice. |
The Critical Importance of Medical Guidance
Because nattokinase acts on the cardiovascular system, it should never be treated as a harmless dietary supplement without medical consideration. The potential for dangerous interactions with prescription drugs and the risks for individuals with pre-existing conditions are significant. Self-substituting a supplement for a prescribed medication is extremely dangerous and has been linked to life-threatening outcomes.
Always consult with a qualified healthcare provider before starting or stopping nattokinase. They can help assess your individual risk factors and determine if it is appropriate for you. For more information on general supplement safety, the Memorial Sloan Kettering Cancer Center offers helpful guidance.
Conclusion
While nattokinase shows promise as a supportive enzyme for cardiovascular health, its potent fibrinolytic and anti-clotting effects mean it is not suitable for everyone. Individuals on blood-thinning or blood pressure-lowering medications, those with bleeding disorders or recent strokes, people undergoing surgery, and women who are pregnant or breastfeeding must avoid nattokinase. Furthermore, those with a soy or natto allergy are at risk of allergic reactions. The unsupervised use of nattokinase is dangerous and should be avoided in favor of professional medical advice to ensure patient safety and proper management of health conditions.
