From Academic Kids

Missing image
Natto eaten on top of rice is always stirred before consumption

Nattō (納豆) is a traditional Japanese dish made from fermented soybeans, popular especially at breakfast. A rich source of protein, nattō and the soybean paste miso formed a vital source of nutrition in feudal Japan. An acquired taste due to its powerful smell and sticky consistency, even in Japan nattō is consumed mostly in the eastern Kanto region.


Appearance and consumption

The first thing noticed by the uninitiated after opening a pack of natto is the very strong smell, akin to strong cheese. Stirring the natto produces lots of spiderweb-like strings. The natto itself has a somewhat nutty, pleasant flavor that belies its odor.

Natto is most commonly eaten at breakfast on top of rice or bread, possibly with some other ingredients as for example soy sauce, some vegetables, or eggs. Natto is also commonly used in other foods, as for example natto sushi, salad, soups, or even with spaghetti or as fried natto.

Natto is an acquired taste, and natto causes many different reactions in people. Some people love the taste and the aroma of natto, whereas other people hate the smell and the appearance. Some manufacturers produce an odorless or low-odor natto. The split opinion about its appearance and taste can probably be compared to Vegemite in Australia and New Zealand, haggis in Scotland, blue cheese in France or lutefisk in Norway and Sweden. Even in Japan, natto is more popular in some areas than in others. Natto is popular in the eastern Kanto region (Tokyo), but less popular in Kansai (Osaka, Kobe). About 50,000 tons of natto are consumed in Japan each year.

Production process

Soybeans in a plantation
Soybeans in a plantation

Natto is made from soybeans, usually a special type called natto soybeans. Smaller beans are preferred, as the fermentation process will be able to reach the center of the bean easier. The beans are washed and soaked in water for 12 to 20 hours. This will increase the size of the beans. Next, the soybeans are steamed for 6 hours, although a pressure cooker can be used to reduce the time. From this point on care has to be taken to keep the ingredients away from impurities and other bacteria, except for the hay bacterium Bacillus natto, which promotes the fermentation process. The beans are mixed with a special sauce containing salt, sugar, and yeast with the bacterium B. natto. Other ingredients may be added by some manufacturers. The mixture is fermented at 40°C for up to 24 hours. Afterwards the natto is cooled, then aged in a refrigerator for up to one week to add stringiness. During the aging process at a temperature of about 0°C, the Bacilli develop spores, and enzymatic peptidases break down the soybean protein into its constituent amino acids.

Historically, natto was made by storing the steamed soy beans in straw, which naturally contains B. natto. The natto was packed in straw and then left to ferment by itself. The fermentation was done either while the beans where buried underground underneath a fire or stored in a warm place in the house as for example under the kotatsu.

End product

Missing image
Today's natto.

Today's mass-produced frozen natto is usually sold in small polystyrene containers. A typical package contains 3 to 4 containers each of 40 to 50 g. Each container's natto goes with a bowl of rice. It also includes a small packet of soy sauce-based seasoning and another packet of yellow mustard. The natto is sometimes frozen and needs to be thawed.


The first production of natto was probably -- like so many other inventions -- an accident. Someone stored the beans in a package of straw or a sack of rice straw, and did not open the package until the beans fermented. Despite the very strong smell and the spoiled appearance, the product was eaten, probably by a very hungry person. Somehow, this accidental discovery became a mainstream product.

The materials and tools needed to produce natto (soybeans and straw) were commonly available in Japan since ancient times, so the discovery could have happened already in the early Jomon period. It may also be possible that the product was discovered independently by numerous people at different times. The sources differ about the earliest origin of natto. One source puts the first use of natto in the Jomon period between 10,000 BC to 300 BC. Another story is that Yoshiie Minamoto was on a battle campaign in northeastern Japan between 1056 and 1063 and another campaign between 1086 and 1088 when one day in 1083 they got attacked while boiling soybeans for their horses. They hurriedly packed up the beans, and did not open the straw bags until a few days later, at which time the beans had fermented. The soldiers ate it anyway, and liked the taste, so they offered some to their commander Yoshiie Minamoto who also liked the taste. A third source calls the origin of natto fairly recent from the Edo period (1603 to 1867).

One significant change in the production of natto happened in the Taisho period (1912 - 1926), when researchers discovered a way to produce the natto yeast containing the Bacillus natto without the need for straw. This greatly simplified the production process and enabled more consistent results.

Medical benefits

Natto is claimed to have many medical benefits, and Japanese often say that eating natto is good for your health. Some of these claims are backed by medical research. Natto for example contains a compound Pyrazine, which not only gives natto its distinct smell, but also reduces the likelihood of blood clotting. An enzyme nattokinase may also reduce blood clotting both by direct fibrinolysis of clots, and inhibition of the plasma protein plasminogen activator inhibitor 1. This may help to avoid thrombosis, as for example in heart attacks, pulmonary embolism, or strokes. An extract from natto containing nattokinase is available as a dietary supplement. Studies have shown that oral administration of nattokinase leads to a mild enhancement of fibrinolytic activity in rats and dogs. It is therefore plausible to hypothesize that nattokinase might reduce blood clots in humans, although clinical trials have not been conducted.

Natto also contains large amounts of Vitamin K, which is involved in the formation of calcium-binding groups in proteins, assisting the formation of bone, and preventing osteoporosis. Vitamin K1 is found naturally in seaweed, liver and some vegetables, while vitamin K2 is found in fermented food products like cheese and miso. Natto has very large amounts of vitamin K2, approximately 870 micrograms per 100g of natto.

Natto also contains many chemicals alleged to prevent cancer, as for example daidzein, genistein, infrabin, phytoestrogen, and the element selenium. However, most of these chemicals can also be found in other soy bean products, and their effect on cancer prevention is uncertain at best. Some sources also claim that natto has a cholesterol-lowering effect.

Natto is also said to have an antibiotic effect, and was used as medicine against dysentery by the Imperial Japanese Army before World War II. Furthermore, natto is said to improve digestion, reduce the effects of aging, and to prevent obesity, although this seems to be based only on an analysis of the chemicals contained in natto, and not on any medical study.

Natto is also sometimes used as an ingredient of pet food, and it is claimed that this improves the health of the pets. The animals also don't seem to mind the smell and sliminess of natto.

See also

Other fermented soy products include douchi, tempeh, and miso. Note that amanatto is not nattō, but rather, beans sweetened with sugar.

External links

fr:Nattō ja:納豆


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