Natto is a traditional fermented food that has been cherished in Japan for centuries. It is made primarily from soybeans, which are fermented with Bacillus subtilis (natto bacteria). Known for its distinctive stickiness and aroma, natto is praised for its health benefits and is a common sight on Japanese dining tables, especially at breakfast.
As a part of Japanese food culture, natto is enjoyed in various ways across different regions. For example, while it may not be very popular in the Kansai region, it is a daily staple in regions like Tohoku and Kanto. In addition to being eaten as a side dish at breakfast, natto can be used as a topping for sushi rolls or udon noodles.

Is Natto Rotten? The Difference Between Fermentation and Spoilage
You may wonder, “Is natto rotten?” In fact, natto is a “fermented” food, not a spoiled one. Fermentation refers to the process where microorganisms break down food into beneficial substances for humans. On the other hand, spoilage occurs when microorganisms cause food to become inedible.
While both fermentation and spoilage are caused by microorganisms, the key difference lies in their effects. Fermentation enhances the flavor and nutritional value of food and aids in digestion. For instance, natto bacteria break down soybeans and produce Vitamin K and probiotics, which improve the nutritional value of natto and promote a healthy gut.
On the contrary, spoilage occurs when microorganisms multiply and turn food into harmful substances. Even natto can spoil if stored improperly, leading to bad smells and discoloration. It’s important to remember that even fermented foods can spoil under unsuitable storage conditions.

The Health Benefits of Natto
Natto is often called a “superfood” due to its high nutritional value. Some of its key health benefits include:
- Vitamin K: Natto is rich in Vitamin K, which is crucial for bone health and blood clotting.
- Probiotics: The natto bacteria promote the growth of good bacteria in the gut, aiding digestion and improving bowel movements.
- Protein: Since natto is made from soybeans, it is a rich source of plant-based protein, making it an excellent protein option.
- Nattokinase: This enzyme, unique to natto, helps dissolve blood clots and supports cardiovascular health.
These nutrients, particularly in Japanese diets, are believed to contribute to longevity and overall well-being.
Conclusion
Natto is a traditional Japanese food made using the natural process of fermentation. Unlike spoilage, fermentation by natto bacteria enhances its nutritional value and offers a range of health benefits. Whether eaten as a breakfast staple or incorporated into other dishes, natto has become deeply rooted in Japanese daily life. By understanding natto’s fermented nature and storing it properly, you can enjoy it both deliciously and healthily.