In 1995, researchers at the National Cancer Center Japan (NCCJ) in Tokyo started an ambitious long-term study that involved tracking the health and dietary choices of more than 92,000 adults to determine whether there was a correlation between eating soy products and certain causes of death. The participants were quizzed about their consumption of 138 different foods and beverages at the beginning of the study, and at the five- and 10-year marks after that, but the researchers were most interested in how much natto, tofu, miso, and soy milk everyone was downing on the reg.
The results of the study were published earlier this year in the the British Medical Journal, and although the authors urged caution when interpreting their data, it did seem to illustrate that a higher intake of fermented soy, like natto and miso, correlated to a lower risk of death by stroke or heart attack. Both men and women who downed 50 grams of fermented soy every day lowered their risk of those particular causes of death by 10 percent, when compared to the study participants who reported the lowest amount of natto and miso consumption.
But natto sales have gotten another recent boost, because some people seem to believe that it can prevent coronavirus. The idea that natto is some kind of powerfully scented panacea isn't a new one: Japan Today reported that in 1992, one physician said that eating natto "can't hurt" when it came to protecting oneself from AIDS.
Natto is undoubtedly one of the world's most divisive foods. It is one of the 80 items on display at the Disgusting Food Museum in Malmö, Sweden (which is temporarily closed due to coronavirus) and it has been described by Japanese news outlet SoraNews24 as "notoriously challenging" to eat. But it's ammonia-like smell and stringy consistency are more readily overlooked during a global pandemic, especially when panicked shoppers convince themselves that fermented soybeans are the immunity booster they've been looking for. According to Japan Today
, some of the Japanese prefectures that are highest in natto consumption have also had the lowest number of confirmed cases of coronavirus—but correlation, causation, etc. etc.
Sales of natto have increased 20 percent over the same time period last year, but the Japan Natto Cooperative Society Federation has suggested that the increased sales could be one of the drivers of those coronavirus-related rumors.
"[S]tores began running out of natto," a spokesperson for the group said. "This may have led some people to circulate unfounded remarks to the effect that natto was effective in warding off the new coronavirus [...] Sold-out food invites even more demand, and also generates misinformation."
Natto was also among the products that Japan's Consumer Affairs Agency has connected to coronavirus-related sales scams. "Peptide contained in natto destroys the membrane of the bacteria that cause pneumonia," one entirely unsubstantiated advertisement said.
"As of now, none of these products has infection-preventive capabilities backed by science,” an agency official told The Asahi Shimbun. "We want people to take appropriate measures against the virus, such as washing their hands.”
If you want to buy a couple of containers of natto, knock yourself out. The strong scent might help facilitate social distancing, but it probably won't make you any less likely to get coronavirus. However, if you develop a serious soybean habit, you might be slightly less likely to die of a stroke in a couple of decades. Nice work, Future You.