The Japanese dish of fermented soybeans often eaten for breakfast is natto.
Natto is made by fermenting whole soybeans with the bacterium Bacillus subtilis var. natto. The process gives the beans a distinctive sticky, stringy texture, a strong aroma, and a savory flavor. Natto is commonly mixed with soy-based sauce, mustard, and chopped Japanese bunching onion, then spooned over rice.
It is strongly associated with breakfast, particularly in eastern Japan, including the Kantō, Tōhoku, and Hokkaido regions. Natto is valued as a convenient protein-rich food and is also known for supplying vitamin K2, though nutritional amounts vary by serving and brand.
Natto is easy to confuse with other soybean foods. Tofu is made by coagulating soy milk, edamame is an immature soybean rather than a fermented product, and miso is a fermented paste made from soybeans and koji. Natto’s intense smell and slippery texture make it an acquired taste, but many people eat it regularly as part of a traditional Japanese meal.