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Natto: The Weirdest Probiotic Food

Natto is a Japanese invention of fermented soybean inoculated with a bacteria called Bacillus subtilis. It is a foul smelling, slimy food that tastes great and has many health benefits.

Natto: The Weirdest Probiotic Food

Natto: The Japanese Fermented Soybean Delicacy

Natto, a traditional Japanese fermented soybean product, is known for its strong smell, unique taste, and slimy texture. Despite its controversial sensory qualities, natto is widely consumed in Japan and is renowned for its health benefits. In this extensive review, we will delve into the history of natto, its early variations, and its evolution into modern commercial products. We will also discuss nattokinase, the mucopolysaccharide texture, and the various health benefits associated with natto consumption.

History of Natto

The origins of natto can be traced back over a thousand years to the Heian period (794-1185) in Japan. The lack of refrigeration at the time necessitated the use of fermentation as a preservation method for various food items, including soybeans. There are several legends surrounding the discovery of natto, but the most widely accepted one involves the Japanese samurai, who fermented soybeans in rice straw to preserve them for long military expeditions. The fermentation process, facilitated by Bacillus subtilis bacteria present in the rice straw, transformed the soybeans into natto.

Early Variations and Stinky Tofu

Natto shares similarities with other fermented soybean products, such as Chinese douchi, Korean doenjang, and Indonesian tempeh. However, one early variation of natto, known as "stinky tofu," stands out due to its particularly strong odor. Stinky tofu, a popular street food in China, is made by fermenting tofu in a brine containing various ingredients, including fermented milk, vegetables, and meat. The fermentation process produces a pungent smell that many find offensive, though the taste is often described as savory and flavorful.

Current Formulations and Commercial Products

Modern natto production involves the controlled fermentation of cooked soybeans with a specific strain of Bacillus subtilis, resulting in a more consistent and standardized product. Commercial natto is typically sold in small polystyrene containers, with the beans submerged in a thin layer of liquid. The fermentation process takes place within these containers, allowing the final product to be consumed directly.

The Smell, Taste, and Cultural Perception

Natto is notorious for its strong, distinctive smell, often compared to dirty socks or ammonia. Even among the Japanese population, the odor can be polarizing, with some people finding it offensive, while others enjoy it. The taste of natto is complex, typically described as very salty, deep, earthy, and burnt. It is often served with rice, soy sauce, and mustard, which help to balance the intense flavor.

Typical Uses in Japanese Cuisine

Natto is traditionally consumed for breakfast in Japan, often mixed with rice and topped with additional ingredients like raw egg, soy sauce, and green onions. It can also be used as a filling for sushi rolls or as a topping for noodles, tofu, and vegetables.


One of the key health-promoting components of natto is nattokinase, an enzyme produced by Bacillus subtilis during fermentation. Nattokinase is known for its fibrinolytic properties, meaning it can break down blood clots, which has potential implications for cardiovascular health.

The Texture: Slimy and Stringy

Perhaps the most distinctive feature of natto is its slimy and stringy texture, which is unlike any other food. This texture is due to the presence of a mucopolysaccharide produced by the Bacillus subtilis bacteria during fermentation. While the sliminess may be off-putting to some, it is considered a desirable quality by natto enthusiasts.

Health Benefits of Natto

Natto is packed with various health benefits,including its rich nutritional profile, which contains high levels of protein, vitamins, and minerals. The fermentation process also enhances the bioavailability of these nutrients, making them more easily absorbed by the body.

In addition to its nutritional benefits, natto has been linked to various health-promoting effects, such as:

  1. Cardiovascular health: Nattokinase, the enzyme present in natto, has been shown to reduce blood clot formation, lower blood pressure, and improve overall cardiovascular health.

  2. Bone health: Natto is rich in vitamin K2, which plays a crucial role in bone metabolism and has been associated with improved bone density and a reduced risk of osteoporosis.

  3. Digestive health: As a fermented food, natto contains beneficial probiotic bacteria that can help maintain a healthy balance of gut microbiota, improving digestion and supporting overall gastrointestinal health.

  4. Immune system support: The probiotics and bioactive compounds found in natto may help strengthen the immune system and protect against infections.

  5. Weight management: Some studies suggest that natto may have a positive impact on weight management due to its high protein content, which can promote satiety and reduce overall calorie intake.


Natto, the traditional Japanese fermented soybean product, has a long history and a unique sensory profile characterized by its strong smell, salty taste, and slimy texture. Despite these controversial qualities, natto has been widely consumed in Japan for centuries and is known for its numerous health benefits.

Modern natto production has evolved to create a more consistent and palatable product, making it more accessible to consumers worldwide. The health-promoting components of natto, such as nattokinase and vitamin K2, along with its probiotic properties, have generated interest in the scientific community and the general public alike.

In summary, natto is a fascinating and complex food with a rich history, unique sensory qualities, and a wide range of health benefits. Its growing popularity outside of Japan attests to the potential of this ancient fermented food to contribute to overall health and well-being.

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