What Is Natto, a Food Deeply Rooted in Japanese Food Culture?

Natto is a fermented soybean food made using natto bacteria (Bacillus subtilis).
In the traditional method, soybeans are thoroughly steamed, cooled, wrapped in rice straw bundles, and then fermented for about one day in the right environment, allowing natural natto bacteria to grow and produce natto.
By the way, this is the traditional method, and today natto is often made using cultured natto bacteria.
It is broadly divided into two types: “itohiki natto” and “shiokara natto (tera natto),” and when people simply say natto, they usually mean “itohiki natto.”
It has long been eaten in Japan as a traditional everyday food, but because of its sticky texture and strong, distinctive smell, some Japanese people do not like it either.
In particular, there are relatively many people in western Japan who dislike natto.
In the past, natto was eaten as a source of nutrition in place of fish and vegetables, but in western Japan fish was easy to obtain, so the habit of eating natto did not take root there.
This historical background is said to be one reason why many people in western Japan still dislike natto today.

“Itohiki natto” is classified into several types depending on its shape, production method, and bean size.
Here, we will introduce three common types of “itohiki natto.”
Even within the same category, the characteristics vary, so use this as a guide when trying or buying natto.

There are various theories about the origin of natto, but its exact beginnings remain unclear.
However, the “Hachimantaro Yoshiie theory” is often cited as one of the leading explanations.
According to this theory, during the late Heian period (794 to 1185), the warrior Minamoto no Yoshiie was on campaign in the Tohoku region when boiled soybeans were wrapped in straw for storage and naturally fermented, becoming stringy.
This is thought to have led to the discovery that natto bacteria living in straw could naturally ferment soybeans.
When the soldiers actually tried eating it, they found it tasty and useful as food, and it is said that the practice eventually spread to farmers as well.
There is also a theory that fermented soybean foods had already existed in various parts of East Asia before that, and that a natto-like food existed as early as the Yayoi period, around the 10th century BC to the mid-3rd century AD.
In any case, both boiled beans and straw are involved, and something born by pure chance developed in a uniquely Japanese way and has continued to the present day.

The word “natto” first appeared in written records in the mid-Heian period work “Shin Sarugakuki.”
The natto mentioned in this text is said to have been shiokara natto, which is not stringy, and it seems to have often been made in temples.
One leading theory says the name “natto” came from a “bean dish” made in the monks’ kitchen, called “nassho.” ※There are various theories.
On the other hand, stringy natto was first confirmed in the Muromachi period (1336 to 1573) in “Shojin Gyorui Monogatari.”
By the mid-Edo period (1603 to 1868), natto had become common enough to appear on the dining tables of ordinary people.
Gradually, the culture of eating natto for breakfast spread, and at that time merchants called “natto sellers” walked around selling it with lively calls.
In the modern era and beyond, production shifted from fermentation in straw to hygienic packaging and machine manufacturing, improving shelf life and distribution, and natto became a common food across Japan.

The most basic way to eat natto is “natto rice,” made by mixing natto with the included sauce and mustard, then placing it over rice.
By the way, it is said that mixing natto adds air to its sticky components, creating a fluffier texture.
The nutritional value does not change depending on how many times you mix it, and there is no single correct answer, so it is best to go with your own preference.
If you find the smell off-putting, adding seasonings such as soy sauce or wasabi can make it easier to eat.
There are also regional and personal differences, but “natto toast” on sliced bread and “natto soup” added to miso soup are also widely enjoyed.

One of natto’s appeals is that it is easy to find and enjoy anywhere in Japan.
It is mainly sold at supermarkets and convenience stores in sets of three to five round or square packs.
Another nice point is the affordable price, at around 100 yen per pack.
Since it does not often appear on restaurant menus, when you visit Japan, try buying it at a supermarket or convenience store, or give it a try at a hotel breakfast buffet.

Mito City in Ibaraki Prefecture, which boasts the highest natto production volume in Japan, is known as the “town of natto.”
Because the Mito Domain, now Mito City, encouraged natto production during the Edo period, the area developed a strong foundation for natto making and was also well suited to securing raw materials.
In the Meiji period (1868 to 1912), Seizaemon Sasanuma of Mito City founded “Tengu Natto” and established natto manufacturing techniques.
Then, with the opening of the Mito Railway, now the JR Mito Line, in 1889, small-bean natto sold in the station plaza as a souvenir and Mito specialty became popular and helped make it known nationwide.
Mito City is not only a production area for natto, but also home to many natto-themed events and facilities, promoting natto culture across the whole region, and it is cherished by local people as more than just a food.

Japan not only has a “town of natto,” but also a “Natto Day.”
In 1981, the Kansai Natto Manufacturers Cooperative designated July 10 as Natto Day in order to boost natto consumption in the Kansai region, including Osaka and Kyoto, where consumption had not been growing.
At first, it was a commemorative day limited to the Kansai region, but in 1992 the National Federation of Natto Manufacturers Cooperatives officially established it again as Natto Day, and it became widely known throughout Japan.
In contrast to the Kansai region, Fukushima, which has one of the highest natto consumption levels in Japan, holds natto sales at supermarkets and other stores on Natto Day.

This article has introduced natto mainly through its origins, types, and recommended creative ways to enjoy it.
Natto is more than just an ingredient, and it continues to be a healthy food that supports the Japanese diet.
Another part of its appeal is the way its taste and how it is eaten vary by person and region, reflecting Japan’s unique food culture and diversity.
Many people are put off by its distinctive smell and stickiness, but that too is part of its character.
If you have never tried natto before, be sure to give it a try at least once.