Claims that nattokinase can “break down” the COVID-19 spike protein have circulated widely, and there is a real peer-reviewed study behind the claim. But the gap between what that study actually showed and what social media posts often imply is large enough that it deserves a careful, unhurried explanation.
Key Takeaways
- A 2022 study published in Molecules found nattokinase degraded SARS-CoV-2 spike protein in a dose- and time-dependent way, but the experiments were done in cell lysates and cell culture, not in living animals or humans.
- The same study found nattokinase also degraded ACE2, the receptor the virus uses to enter cells, and even degraded an unrelated housekeeping protein (GAPDH), indicating nattokinase acts as a broadly non-specific protease rather than a spike-protein-targeted treatment.
- An earlier 2021 study found natto extract itself had direct antiviral activity against SARS-CoV-2 in vitro, which is what prompted researchers to isolate nattokinase as a likely active component.
- In vitro results do not establish that oral nattokinase supplements reach meaningful concentrations at relevant tissue sites in the human body, or that they have any effect on an actual infection or on spike protein from vaccination.
- No clinical trial has tested nattokinase for COVID-19 treatment, prevention, or post-vaccination spike protein clearance in humans.
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What the Actual Study Found
The key paper is “Degradative Effect of Nattokinase on Spike Protein of SARS-CoV-2,” published by Tanikawa and colleagues in the journal Molecules in 2022. Researchers took cell lysates and live cells engineered to express the SARS-CoV-2 spike protein and incubated them with a dilution series of nattokinase, across a range of concentrations [5]. Using Western blotting to measure protein levels, they found spike protein degradation that increased with both higher nattokinase concentration and longer incubation time, with degradation becoming apparent within the incubation times tested [5]. Immunofluorescence imaging supported the same conclusion for spike protein sitting on the surface of intact cells.
The Detail Most Coverage Leaves Out
The same study also tested whether nattokinase degraded ACE2, the human cell-surface receptor the virus binds to enter cells, and found that it did. It further found that GAPDH, a completely unrelated housekeeping protein present in essentially all cells and used as a lab loading control, was degraded by nattokinase under the same conditions. The researchers themselves interpreted this as evidence that nattokinase’s protease specificity is low, meaning it is breaking down a wide range of proteins it comes into contact with in a test tube, not selectively hunting the spike protein. That is an important nuance that changes how the headline finding should be read.
Research note: A long-COVID treatment review says there are no human studies suggesting nattokinase is beneficial for long COVID, and none underway or planned in the near future [6].
In Vitro Is Not the Same as In You
“In vitro” means the experiment happened in isolated cells or cell extracts in a lab dish, not inside a living organism. That distinction matters enormously here. Oral nattokinase has to survive digestion, get absorbed into circulation, and reach a relevant concentration at a relevant tissue site to have any of the effects seen in a petri dish. Existing research on oral nattokinase does document changes in blood fibrinolytic markers after dosing (a single dose raised D-dimer in 12 healthy young men, with all changes staying within the normal range), but EFSA noted that the supplied data could not show whether active nattokinase is absorbed, and that is a separate question [3][4] from whether it reaches spike protein-relevant concentrations at relevant sites in a way that would replicate the in vitro degradation study.
The Study That Came Before It
This 2022 spike protein paper built on an earlier 2021 study published in Biochemical and Biophysical Research Communications, which found that natto extract itself, the whole fermented soybean food extract rather than purified nattokinase, had direct antiviral activity against SARS-CoV-2 in a cell culture infection model. That earlier finding is part of why researchers went looking for nattokinase specifically as a possible active component, and it is a legitimate area of ongoing scientific interest, not a debunked claim. It simply has not yet progressed past laboratory-stage evidence.
What Has Not Been Studied
No published clinical trial has tested oral nattokinase supplementation in humans for COVID-19 prevention, COVID-19 treatment, long COVID symptoms, or clearance of spike protein following vaccination. Claims framing nattokinase as a way to “detox” from vaccination are extrapolating from a non-specific in vitro protease effect on cultured cells, several steps beyond what the actual research has demonstrated. Readers interested in this area should treat it as an open scientific question worth watching, not a settled clinical recommendation.
The closest thing to a direct test of the downstream claim points away from it. Researchers exposed amyloid microclots isolated from plasma to three fibrinolytic enzymes, nattokinase among them, both alone and combined with ultrasound. Ultrasound on its own broke the clots up substantially; adding any of the enzymes produced no statistically significant further effect at the lower frequencies tested, and the authors concluded that mechanical force, not enzyme activity, was doing the work.[1]
Anyone researching this topic should also know that the most clinical-looking result circulating in it no longer stands. A small case series reporting symptom resolution in patients given a nattokinase-containing protocol has since been formally retracted.[2] It is listed in the references below so it can be recognised, not because it supports anything; a retracted paper is not evidence, and it continues to be shared as though it were.
Frequently Asked Questions
Did a real study show nattokinase breaks down the COVID spike protein?
Yes, a 2022 peer-reviewed study in Molecules found nattokinase degraded spike protein in cell lysates and cultured cells in a dose- and time-dependent way. That is a real laboratory finding, though it does not establish a clinical effect in humans.
Does this mean nattokinase treats or prevents COVID-19?
No. The research is entirely in vitro (cell culture and cell lysates), and no clinical trial has tested nattokinase for COVID-19 prevention or treatment in humans. Extrapolating a lab finding to a treatment claim goes beyond what the study actually demonstrated.
Is nattokinase specific to the spike protein, or does it break down other proteins too?
The same study found nattokinase also degraded ACE2 and an unrelated housekeeping protein (GAPDH) under the same conditions, which the researchers themselves noted indicates low protease specificity rather than a targeted spike-protein effect.
Can nattokinase clear spike protein after vaccination?
This has not been studied in humans. The claim extrapolates from a non-specific in vitro protease effect observed in cell culture, and no research has evaluated it in the context of vaccination specifically.
These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease. Always talk to your doctor before starting nattokinase, especially if you take blood thinners or have an upcoming surgery.
References
- Rasouli et al. Investigation of the synergistic effect of enzymatic and ultrasound-induced amyloid microclot degradation. Journal of Thrombosis and Thrombolysis (2026). PMID 41405757
- Zeballos et al. Post spike syndrome (PSS): simple solution leading to resolving results, five cases report. IDCases (2025). RETRACTED. Listed only to flag the retraction; not evidence of benefit. PMID 40671933
- Yuko Kurosawa et al. A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles. Scientific Reports (2015). PMID 26109079
- European Food Safety Authority (EFSA NDA Panel) Safety of fermented soybean extract NSK-SD as a novel food pursuant to Regulation (EC) No 258/97. European Food Safety Authority (EFSA NDA Panel) (2016). source
- Tanikawa T et al. Degradative Effect of Nattokinase on Spike Protein of SARS-CoV-2. Molecules (Basel, Switzerland) (2022). PMID 36080170
- Baptista SN et al. Candidate treatments for long COVID: a narrative review of expert and patient-driven priorities. Frontiers in medicine (2026). PMID 41836927
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
