Natto is a traditional Japanese food made from whole soybeans that have been fermented with Bacillus subtilis var. natto. It has a sticky, gooey texture, umami taste, and a strong smell. Natto is often served as a breakfast food with rice and is frequently eaten as natto gohan (natto on rice) . It is also occasionally used in other foods, such as natto sushi (nattōmaki), natto toast, in miso soup, tamagoyaki, salad, as an ingredient in okonomiyaki, chahan, or even with spaghetti. Sometimes soybeans are crushed before fermenting.

Natto is made by steaming or cooking soaked soybean seeds, inoculating them with the bacterium Bacillus subtilis, and allowing them to ferment over time. The fermentation process gives natto its slimy, sticky, and stringy texture. Natto is rich in protein, vitamins, minerals, and probiotics. It contains more vitamin K2 than any other known food on the planet. A 3.5-ounce (100-gram) portion of natto provides 211 calories, 11 grams of fat, 13 grams of carbs, 5 grams of fiber, and 19 grams of protein. Natto is also linked to various health benefits, which range from stronger bones to a healthier heart and immune system.