[FALSE] Does a study in Japan prove natto can inhibit alpha variant?

Screenshot of the Facebook post.

The Claim and Our Verdict

• The claim: A Facebook post published July 15, 2021, claims that a study in Japan proves natto can inhibit alpha variant of COVID-19.
• Fact-checking:
  • The claim is based on a study published July 13, 2021 in Biochemical and Biophysical Research Communications. The study shows that the infectivity of BHV-1 (a type of bovine herpesvirus) and SARS-CoV-2 (a new coronavirus that causes COVID-19), including the N501Y mutation, are inhibited after being incubated with natto extract. N501Y mutation could be included in variants such as alpha, beta, and gamma. Thus, the inhibition is not confined to alpha variant.
  • The study’s results only indicate that the effective component in natto might be “heat-sensitive serine-protease(s),” which may degrade the spike protein that enables infectivity of the virus. Further research is needed because researchers have yet to specify the component and confirm its effects.
  • A press release published by Tokyo University of Agriculture and Technology claims that the study was based on in vitro experiments using cultured cells outside the human body. It cannot conclude that eating natto can combat COVID-19. Thus, the claim that natto can inhibit alpha variant is not accurate and could be misleading. Tetsuya Mizutani, one of the co-authors of this paper, is a professor at Tokyo University of Agriculture and Technology.
• Our ruling: Therefore, we rate the claim as FALSE.

News Brief

A Facebook post published July 25, 2021, claims that natto can inhibit alpha variant of COVID-19.

As of the issuance of this report, the post had been shared 96 times, and had received 19 comments and 299 likes or reactions.

Fact-checking

In a study published July 13, 2021 in the journal, Biochemical and Biophysical Research Communications, researchers used natto extract derived from the mixture of natto and phosphate-buffered saline (PBS), rather than using natto directly.

Screenshot of the paper in the journal, Biochemical and Biophysical Research Communications.

Researchers discovered that the infectivity of some viruses is inhibited due to “proteolysis” (degrading of proteins). The viruses are BHV-1 (a type of bovine herpesvirus) and SARS-CoV-2, including the mutation N501Y. N501Y may be included in several mutant strains of COVID-19, such as alpha, beta, and gamma variants. It is not confined to alpha variant.

The study also conducted controlled experiments. One group of the natto extract was heated at the temperature of 100 °C for 10 minutes, and the other group was treated with protease inhibitor. Results show that in both groups, the infectivity of SARS-CoV-2 and BHV-1 was restored. Analysis shows the effective component in natto extract might be one or several types of “heat-sensitive serine-protease(s).” However, researchers have yet to conclude how this component takes effect.

According to the experiment results, it might indicate that the spike protein of SARS-CoV-2 was degraded by the protease (enzyme that degrades proteins) which is a compound in natto extract, thus the infectivity of the virus was inhibited. It also discovered that natto extract could degrade the spike protein of alpha variant.

This paper does not aim to study whether eating natto can prevent COVID-19, as it is only confined to studying the effects of natto extract as a chemical substance and how it works in laboratory environment. It cannot prove eating natto has the same effect. Thus, it’s unclear whether eating natto can prevent COVID-19.

A press release published by Tokyo University of Agriculture and Technology further clarifies the research. Tetsuya Mizutani, one of the co-authors of this paper, is a professor at Tokyo University of Agriculture and Technology.

Screenshot of the press release published by Tokyo University of Agriculture and Technology.

In the abstract section, it says, “This study is an experiment using cultured cells outside human body. It cannot prove that eating natto can prevent COVID-19.”

However, caption of the claim reads, “natto can degrade the spike protein of coronavirus.” It does not clearly state whether it refers to natto as a food or natto extract as a chemical substance. Although the claim says in the end, “the current study didn’t provide evidence that infectivity of the virus can be inhibited simply by eating natto,” the comments suggest that most readers had been misled to believe that eating natto can prevent COVID-19. Therefore, the claim is inaccurate and misleading.

Screenshot of the Facebook post’s comments.