Nattokinase: The Natural Enzyme That Breaks Down the COVID-19 Spike Protein

Nattokinase is a natural enzyme found in the traditional Japanese food natto, pictured above.

What Is Nattokinase?

Nattokinase is an enzyme produced by Bacillus subtilis var. natto during the fermentation of soybeans to make natto. It has been used in Japan for centuries, mainly for its ability to support cardiovascular health by dissolving blood clots and improving circulation. Scientists have long known that nattokinase possesses fibrinolytic, antithrombotic, and anti-inflammatory effects, and that it can safely be consumed as a dietary supplement (Sumi et al., 1987; Dabbagh et al., 2014).

In recent years, researchers have begun exploring nattokinase’s broader biological benefits, including its impact on inflammation, blood pressure, and even viral activity. The 2022 Josai University study took this research a step further, investigating whether nattokinase can interact directly with the spike protein of SARS-CoV-2—the part of the virus that binds to human cells.

Why the Spike Protein Matters

The spike (S) protein of SARS-CoV-2 is the key that allows the virus to enter human cells. It attaches to a receptor on the surface of cells called ACE2, enabling infection. If the spike protein is damaged or degraded, the virus loses its ability to enter and infect cells effectively.

That’s why the research team focused on whether nattokinase could degrade the spike protein—essentially breaking it down and rendering it inactive.

How the Study Was Conducted

The researchers used human cell lines (HEK293 cells) engineered to express the SARS-CoV-2 spike protein. These cells were then exposed to various concentrations of nattokinase to determine whether the enzyme could degrade the protein.

Through a series of Western blot analyses—a laboratory technique that identifies specific proteins—the team observed that nattokinase broke down the spike protein in both dose- and time-dependent ways. In other words, the more nattokinase was used and the longer it was allowed to work, the more spike protein it degraded.

Importantly, the study also showed that the degradation effect was enzymatic, meaning it came directly from nattokinase’s natural protein-dissolving activity. When the enzyme was heated (which destroys its active properties) or when protease inhibitors were added (which block enzyme activity), the spike protein was no longer broken down. This confirmed that nattokinase’s protease activity was the driving force behind the degradation.

Nattokinase Works Without Damaging Cells

One of the most notable findings was that nattokinase was able to degrade spike proteins on the surface of human cells without harming the cells themselves. The team confirmed this using fluorescent imaging techniques that measured how much spike protein remained after treatment.

At concentrations that effectively degraded the spike protein, there was no evidence of cytotoxicity—meaning nattokinase did not damage or kill the host cells. This makes nattokinase particularly promising as a gentle yet powerful natural compound for supporting the body’s defense mechanisms.

Broader Implications for Health

The study also found that nattokinase can degrade not only the spike protein but also ACE2 and RBD (receptor-binding domain) proteins involved in viral attachment and entry. While this means the enzyme is not highly selective—it can break down multiple proteins—it also highlights its potential role in reducing viral infectivity and clearing harmful proteins from the body.

Beyond its potential effects on viral proteins, nattokinase is known for its cardiovascular, anti-inflammatory, and neuroprotective properties. Because many people with severe COVID-19 also suffer from cardiovascular complications, the researchers suggest that nattokinase may be particularly useful for this group. Its ability to reduce blood clotting, improve circulation, and support vascular health make it a valuable alternative to traditional pharamceuticals.

A Step Toward Natural Support for Viral Defense

Nattokinase and natto extracts could represent a new generation of natural therapeutic agents that help protect against SARS-CoV-2 infection by targeting the spike protein directly.

Unlike pharmaceutical antivirals, nattokinase is a naturally derived enzyme with a long history of safe human use. The research suggests that it helps the body neutralize and break down viral components through natural enzymatic activity.

Conclusion

The Josai University study provides compelling evidence that nattokinase, a natural enzyme found in fermented soybeans, degrades the SARS-CoV-2 spike protein in a safe, dose-dependent manner. By breaking down this essential viral protein, nattokinase helps block the virus’s ability to infect cells.

These findings expand the known benefits of nattokinase beyond cardiovascular health, showing its potential as a natural, multifunctional compound that supports both circulatory and immune system resilience.

Reference

Tanikawa, T., Kiba, Y., Yu, J., Hsu, K., Chen, S., Ishii, A., Yokogawa, T., Suzuki, R., Inoue, Y., & Kitamura, M. (2022). Degradative effect of nattokinase on spike protein of SARS-CoV-2. Molecules, 27(17), 5405. https://doi.org/10.3390/molecules27175405