Natto is an ancient Japanese food made from soybeans. It is soaked and fermented, which makes the soybeans quite sticky, and produces a springy or web effect between each bean. Often considered an acquired taste, the fermenting process makes the smell of natto very strong, and to some not used to the dish, unpleasant. It also tends to produce bad breath, though a vigorous tooth brushing usually solves this problem.
In certain parts of Japan, natto holds great popularity. It may be eaten as a breakfast food, sometimes with a little sugar, or may be served over rice. Some prefer to add sauces to natto and rice, and may use different hot mustards, soy sauce, quail eggs or grated radishes as a topping. It is quite nutritious and low in calories, with about 7 to 8 grams of protein and only about 90 calories per serving.
Natto is also celebrated for its high amounts of vitamin K. It also is high in a number of anti-oxidants, particularly selenium. Natto also contains a protein called nattokinase, which may be a natural blood thinner. Since the soybeans are fermented and grow bacteria, it is also a probiotic food.
The traditional method for preparing natto dates back at least 3,000 years, and some food historians suggest it may have been prepared 10,000 years ago. Some suggest that it may have been Chinese in origin, but it is now considered a primarily Japanese food. Stories about the origins suggest that natto may have been discovered accidentally when soldiers in a hurry packed leftover cooked soybeans and didn't open them again for several days.
Most natto is purchased premade, and not often made at home. It is usually created by adding the bacteria Bacillus subtilis formerly known as Bacillus natto, to the soybeans during fermentation. This is what produces the sticky soybeans and the strong smell.
Many people who try natto for the first time find the flavor to be nutty and a bit sharp, better tasting than smelling. Others feel this food is bland and think it needs additional flavoring. For those who cannot get past the smell, there are some companies that have produced low odor natto, and these might be more palatable.
Not every person in Japan enjoys natto, and it is most popular in eastern parts of the country. It is also hard to find outside of Japan, though occasionally Asian markets will stock it in the frozen section. It may also be possible to find natto ice cream or dried natto, which is eaten like nuts or chips. In Korea, a similar dish includes fermented soybeans and is called cheongguikjang. The Chinese also make a fermented black bean dish called douchi.