Natto - Japan's Gift for Health and Longevity
Emilia Szymańska
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Diets Premium Expert • 17.03.2026
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Scientifically reviewed by a clinical dietitian:
This article has been peer-reviewed for adherence to IŻŻ, WHO, and PTGiP clinical nutritional standards.
| Diets Premium Expert Emilia Szymańska | min read 6 min | Scientifically reviewed by a clinical dietitian 17.03.2026 |
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Key Takeaways
Japan, captivating the world for centuries with its rich culture, tradition, and extraordinary culinary diversity, offers a cuisine that is a synthesis of flavors, textures, and techniques, and enjoys international acclaim. Food in this country is not only a way to alleviate hunger but also a form of art and an element of culture. One of the unique dishes in this cuisine is Natto - fermented soybeans with a specific, sticky consistency and intense, concentrated aroma. While the taste of this dish may be controversial to many, for Asians it is a true culinary delight.
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What precisely is natto?
Natto is a traditional Japanese dish prepared from soybeans that are soaked, cooked, and then fermented in the presence of bacteria from the genus Bacillus subtilis var. natto. Unlike other microorganisms, these create a basic environment, not an acidic one, which imparts an unparalleled flavor to the dish. The fermentation process results in sticky soybeans with a piquant, slightly nutty taste and an aroma reminiscent of that of long-aged cheese (M. Afzaal et al. 2022).
How to consume natto
In Japanese culture, natto often serves as a supplement to breakfast, typically in the form of a delicate, steamed rice dish. This dish is often served with freshly chopped vegetables, crispy nori flakes, pieces of creamy avocado, or spicy kimchi. There is also another method of serving natto by being an ingredient in a dish known as Tamago kake gohan, or raw egg served with rice. The aforementioned ways of serving natto are considered the most traditional. Younger generations of Japanese greatly experiment with fermented soybean and add it to sandwiches with mayonnaise and cheese, salads, soups, noodles, and egg dishes such as omelets or scrambled eggs (J. Sherman 2023).
Nutrient content of fermented soybean products natto
Natto, a soy product produced through fermentation, not only boasts a unique flavor, but also exceptional nutritional values. It is primarily a source of high-quality protein – in 100 g it contains up to 19 g of this macronutrient. Natto in this form also contains large amounts of fiber, iron, potassium and calcium, as well as certain amounts of B vitamins, especially B6 and folic acid. Noteworthy is the fact that natto has a very high content of vitamin K2, nearly 1000 µg/100 g, which is significantly higher than in other products (Jarosz et al., 2021).
Menachinone-7, alternatively known as Vitamin K2 MK7
Menachinone-7, alternatively known as Vitamin K2 MK7, is a form of vitamin K that plays a crucial role in the proper functioning of the skeletal and circulatory systems. It is naturally found in fermented dairy products, eggs, yeast, fermented soybean (natto), and rice cake. Furthermore, it is a common ingredient in dietary supplements available on the market. Vitamin K2 MK-7 is characterized by its long isoprenoid chain, which allows it to have a longer-lasting effect in the body compared to other forms of this vitamin, making it particularly effective (M. Halder et al. 2019).
Natto and its impact on health: research and discoveries
Natto, a fermented Japanese dish, is known for its high content of vitamins, proteins, and enzymes. The main active ingredient in natto is nattokinase, an enzyme with potential antithrombotic properties. It works by breaking down fibrin, a protein responsible for forming clots, thereby reducing the likelihood of clots and improving blood flow (H. Chen et al. 2018). Additionally, regular intake of natto can help lower blood pressure by expanding blood vessels, which in turn can reduce the risk of cardiovascular diseases such as stroke (G. S. Jensen et al., 2016). In a study by M. Afzaal et al. (2022), it was found that natto also lowers the level of so-called bad cholesterol LDL and triglycerides, while simultaneously increasing the level of so-called good cholesterol HDL, thereby enhancing the cardioprotective effect. Moreover, natto also contains antioxidants such as isoflavones and vitamin E, which help protect cells from oxidative stress and the resulting damage, supporting heart health and reducing the risk of cardiovascular diseases (S. Nakai, M. Fujita, Y. Kamei, 2020).
The digestive system
Natto plays a pivotal role in maintaining the health of the digestive system due to its prebiotic and probiotic attributes. The fibers present in this traditional Japanese cuisine support digestive processes, enhance intestinal peristalsis, and avert constipation. Moreover, it may contribute to achieving and upholding optimal body weight by managing blood glucose levels and amplifying satiety after meals. Additionally, natto encompasses beneficial probiotic bacteria that support the balance of gut microbiota, facilitate digestion (e.g., through enzyme production), and fortify the intestinal barrier, thereby decreasing intestinal permeability and preventing inflammatory disorders and autoimmune diseases.
The skeletal system
As previously mentioned, natto is one of the richest sources of vitamin K2 MK7, which is crucial for the proper functioning of the skeletal system. This particular form of Vitamin K plays a key role in depositing and maintaining calcium in bone tissue. Research shows that vitamin K2-supplementation can protect the body from loss of bone mineral density, which reduces the likelihood of bone fractures, especially in older individuals (S. S. Salma Ahmad et al. 2022). 100 g of natto provides up to 17% of the daily phosphorus requirement, which is essential for building and maintaining healthy bones through the process of mineralization (L. Vannucci et al. 2018). Furthermore, fermented soy, from which natto is made, also delivers other nutrients necessary for maintaining the health of the skeletal system, such as protein, potassium, phosphorus, or magnesium, which exhibit proven effects in preventing osteoporosis and supporting good bone health (M. Muñoz, K. Robinson, A. Shibli-Rahhal 2020).
Bodily Immunity
Natto exerts a particularly beneficial influence on bodily immunity. This is primarily due to the high protein content it possesses, which provides the body with necessary amino acids for the production of antibodies and cells responsible for immunity, protecting the body from infections. Additionally, the high level of vitamin K supports the production of cytokines, or chemical substances involved in inflammatory responses. Moreover, fermented soybeans in natto contain beneficial probiotic bacteria that contribute to maintaining the balance of gut microbiota. This balance functions as a physical barrier against pathogens and is also involved in the production of immune cells. Thus, consumption of natto can contribute to strengthening the body's natural defense mechanisms and support overall immunity (M. Lefevre et al. 2015).
Natto as a possible elixir of longevity?
In 2020, the results of a 15-year study of 92,915 Japanese individuals aged 45 to 74 years were published in the highly respected medical journal BMJ, which aimed to evaluate the impact of consuming various soy products on mortality. It was found that individuals who consumed at least 45 grams of fermented soy products per day had a 15% lower risk of death from all causes compared to those who did not. This observation was particularly notable in the case of the product natto. The group of individuals who regularly consumed natto exhibited a 23% lower proportion of deaths (R. Katagiri et al., 2020). These data suggest potential health benefits associated with the consumption of fermented soy products such as natto in the context of longevity and reducing the risk of death. However, further investigations are necessary to confirm these effects and understand the underlying mechanisms.
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