Nattokinase—a serine protease enzyme derived from the traditional Japanese fermented food natto—has become one of the most discussed natural compounds in the spike protein detoxification conversation. The 2022 Tanikawa study in Molecules provided the first direct evidence that nattokinase can degrade SARS-CoV-2 spike protein in laboratory conditions. But what does the full body of research actually show, and how does this translate to human use?
The Tanikawa Study: Direct Spike Protein Degradation (2022)
The landmark study from Tanikawa et al. at the University of Tokushima demonstrated nattokinase's degradative effect on spike protein through two experimental approaches:
In Vitro (Cell Lysate) Experiments
When cell lysates expressing SARS-CoV-2 spike protein were incubated with nattokinase:
- Dose-dependent degradation: Spike protein (both full-length S and S2 subunit) was progressively degraded at concentrations from 500 ng/mL to 32 μg/mL
- Time-dependent degradation: At 1 μg/mL, spike protein degradation was observed after 60–180 minutes of incubation, but not at 10 or 30 minutes
- Enzymatic mechanism confirmed: Heat inactivation (100°C, 5 min) eliminated the effect; protease inhibitors (particularly serine protease inhibitors like AEBSF and aprotinin) blocked degradation
- RBD and ACE2 also degraded: Both the receptor binding domain (RBD) of spike and human ACE2 were degraded by nattokinase at 7.5 μg/mL
Cell Surface Experiments
When nattokinase was added to the culture medium of cells expressing spike protein on their surface:
- At 25 μg/mL: spike protein-positive surface area decreased to ~0.3 of control
- At 2.5 μg/mL: decreased to ~0.7 of control
- No cytotoxicity was observed at these concentrations (confirmed by MTT assay)
- Importantly, total cellular spike protein (measured by Western blot of whole cell lysates) did not change, suggesting nattokinase acts specifically on extracellular/surface-exposed protein
Key limitation noted by the authors: Nattokinase has relatively low protease specificity. GAPDH (a housekeeping protein) was also degraded in the cell lysate experiments, indicating it cleaves proteins broadly, not just spike protein.
Fibrinolytic and Cardiovascular Effects
Beyond spike protein degradation, nattokinase has well-documented fibrinolytic (clot-dissolving) properties that are directly relevant to long COVID pathology:
Human Clinical Evidence
- Acute fibrinolysis: A single oral dose of 2,000 FU (100 mg) significantly elevated D-dimer levels at 6 and 8 hours, and blood fibrin/fibrinogen breakdown products at 4 hours post-ingestion (p < 0.05)
- Blood pressure reduction: A meta-analysis of 6 RCTs (546 participants) found nattokinase supplementation significantly reduced systolic BP (MD = –3.45 mmHg, p < 0.00001) and diastolic BP (MD = –2.32 mmHg, p < 0.00001) vs. placebo
- von Willebrand factor: Average levels reduced by 15% after 8 weeks of supplementation in hypertensive patients
- Safety at high doses: Tested up to 80,000 FU daily without serious adverse events in clinical settings
What Nattokinase Does NOT Do (Based on Current Evidence)
- No proven carotid artery benefit: A 3-year RCT (265 participants, 2,000 FU/day) found no significant difference in carotid intima-media thickness progression vs. placebo
- No consistent lipid effects: Meta-analysis showed no reliable cholesterol-lowering at standard doses
- No human spike protein clearance data: No published study has directly measured spike protein levels in humans before and after nattokinase supplementation
How Nattokinase Fits the McCullough Protocol
The McCullough Base Spike Detoxification Protocol (published in Journal of American Physicians and Surgeons, Fall 2023) positions nattokinase as the primary proteolytic agent:
| Component | Dose | Primary Mechanism |
|---|---|---|
| Nattokinase | 2,000 FU twice daily | Proteolytic spike degradation + fibrinolysis |
| Bromelain | 500 mg once daily | Spike cleavage via cysteine protease activity |
| Curcumin | 500 mg twice daily | Anti-inflammatory + ACE2 binding inhibition |
Duration: 3–12 months. Take nattokinase on an empty stomach. Caution with anticoagulants.
Understanding Fibrinolytic Units (FU)
Nattokinase potency is measured in fibrinolytic units (FU), not milligrams. This is critical because enzyme activity varies independently of mass. A claim of "100 mg nattokinase" without FU specification is essentially meaningless.
- Standard clinical dose: 2,000 FU per serving (typically 100 mg)
- Measurement standard: Japan Bio Science Labs (JBSL) 1998 method or equivalent fibrin plate assay
- Industry body: Japan Nattokinase Association (JNKA) maintains standardization
- Key: always look for FU on the label, not just mg
The Bottom Line
Nattokinase demonstrates clear spike protein degradation in laboratory conditions and has well-established fibrinolytic properties confirmed in human trials. Its safety profile is strong, with the primary concern being bleeding risk in patients on anticoagulants. However, no human trial has yet directly measured whether oral nattokinase reduces circulating spike protein levels in long COVID patients. The gap between promising in vitro data and clinical proof remains the most important caveat for consumers.
This article is for informational purposes only and does not constitute medical advice.
References
- Tanikawa T, et al. Degradative Effect of Nattokinase on Spike Protein of SARS-CoV-2. Molecules. 2022;27(17):5405.
- McCullough PA, Wynn C, Procter BC. Clinical Rationale for SARS-CoV-2 Base Spike Protein Detoxification. J Am Physicians Surg. 2023;28(3):90–93.
- Kurosawa Y, et al. A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles. Sci Rep. 2015;5:11601.
- Hodis HN, et al. Nattokinase atherothrombotic prevention study. J Am Heart Assoc. 2021.
- Li Z, et al. Nattokinase Supplementation and Cardiovascular Risk Factors: Meta-analysis. Evid Based Complement Alternat Med. 2023.
- Jensen GS, et al. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor. Integr Blood Press Control. 2016;9:95–104.
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