Does Natto Have Any Health Benefits? A Scientific Look at Japan's Superfood

November 14, 2025 •

4 min read

According to Japan's National Cancer Center, a 2020 study announced that high consumption of the traditional fermented soybean dish, natto, lowers overall mortality risk. But does natto have any health benefits that truly qualify it as a modern superfood? Beyond its distinctive taste and texture, compelling scientific evidence points to its powerful nutritional profile.

Quick Summary

A fermented soybean superfood, natto is a powerhouse of vitamin K2, nattokinase, and beneficial probiotics, offering significant support for cardiovascular, bone, and gut health.

Key Points

Heart Health: Natto contains nattokinase, an enzyme that acts as a natural blood thinner by dissolving fibrin, potentially reducing the risk of heart disease and lowering blood pressure.
Bone Health: It is the richest food source of highly bioavailable vitamin K2 (MK-7), which is essential for bone mineral density and preventing calcium buildup in arteries.
Gut Health: As a fermented food, natto is packed with probiotics, including Bacillus subtilis, which promotes a healthy and balanced gut microbiome.
Digestive Support: High in both probiotics and fiber, natto improves gut motility and digestion, helping to prevent constipation and other gastrointestinal issues.
Nutrient-Dense Protein: Natto offers a complete, highly digestible, and nutrient-rich plant-based protein source, providing essential amino acids, fiber, and micronutrients like iron and manganese.
Reduced Mortality Risk: A 2020 study by Japan's National Cancer Center correlated high natto consumption with a lower overall mortality risk.

What is Natto?

Natto is a traditional Japanese food made by fermenting soybeans with the bacterium Bacillus subtilis var. natto. This process is responsible for its characteristic stringy, sticky texture and pungent aroma, which can be off-putting for some, yet cherished by many in Japan. The fermentation not only transforms the beans but also significantly enhances their nutritional value, creating unique compounds not found in unfermented soybeans. For centuries, it has been a staple, often served over rice with mustard and soy sauce, and its reputation as a health-promoting food is now being backed by scientific research globally.

Key Nutritional Components

Natto's impressive health benefits stem from its rich and unique nutritional composition. During fermentation, the soybeans become more digestible, and their nutrient content is amplified, leading to a concentration of valuable compounds like Vitamin K2, nattokinase, and beneficial probiotics.

Probiotics and Gut Health

As a fermented food, natto is a potent source of probiotics, specifically the Bacillus subtilis strain used in its production. These live microorganisms help to balance the gut microbiota, which is crucial for overall digestive function and immune system strength.

Improved Digestion: The probiotics and high fiber content support gut motility and help alleviate digestive issues such as constipation.
Enhanced Immune Function: A healthy and diverse gut microbiome is a key pillar of a robust immune system. By promoting the growth of beneficial bacteria, natto helps the body fight off pathogens.
Reduced Inflammation: The bacterial cultures in natto, along with other bioactive compounds, may help reduce chronic inflammation in the gut, which can lead to other metabolic disorders.

Nattokinase and Heart Health

One of the most notable compounds in natto is nattokinase, a powerful enzyme with demonstrated fibrinolytic (blood clot-dissolving) activity. This enzyme is the focus of much research regarding its cardiovascular benefits. Regular consumption of natto may aid in preventing the formation of blood clots, which is a major factor in heart attacks and strokes. Additionally, studies have suggested that nattokinase can have a modest effect on lowering blood pressure.

Vitamin K2 and Bone Health

Natto is an exceptional, and one of the only plant-based, sources of Vitamin K2, specifically the MK-7 isoform, which is highly bioavailable and effective in the body. Vitamin K2 plays a vital role in regulating calcium metabolism. It helps activate proteins that guide calcium to your bones and teeth, preventing its accumulation in soft tissues and arteries.

Prevents Osteoporosis: Multiple studies have linked regular natto consumption with improved bone mineral density (BMD) and significantly reduced rates of age-related bone loss in postmenopausal women.
Reduces Fracture Risk: Research suggests that a consistent intake of natto may lower the risk of osteoporotic bone fractures.
Supports Vascular Health: By directing calcium away from arterial walls, vitamin K2 from natto also contributes to reducing arterial stiffness and calcification, further supporting cardiovascular health.

Natto vs. Other Fermented Soy Foods

Natto is often compared to other popular fermented soy products like miso and tempeh. While all offer health benefits, their nutritional profiles and specific advantages differ significantly.


Feature	Natto	Miso	Tempeh
Fermentation Agent	Bacillus subtilis var. natto	Aspergillus oryzae mold	Mixed culture, often Rhizopus oligosporus mold
Key Unique Compound	Nattokinase (fibrinolytic enzyme), abundant Vitamin K2	Contains antioxidants, gut-supporting compounds	Rich in prebiotics and protein
Vitamin K2	Extremely high levels (especially MK-7)	Minimal amounts	Lower than natto
Nattokinase	Rich source	None	None
Texture	Sticky, stringy, soft beans	Paste-like	Firm, cake-like

How to Incorporate Natto into Your Diet

While its unique characteristics can be challenging, there are many ways to enjoy natto and reap its benefits:

Classic over rice: The traditional Japanese method. Stir the natto vigorously with the included sauce and mustard until foamy, then serve over warm rice.
Add toppings: Experiment with toppings to mask the strong flavor. Common additions include chopped green onions, kimchi, a raw egg, or shredded seaweed.
Mix into sauces: Stir it into miso soup, curry, or pasta sauce, though some live bacteria may be lost with heat.
Try it in a wrap: Add natto to a tortilla with other flavorful ingredients like vegetables and a creamy dressing.
Dried or Fried: For those who dislike the texture and smell, dried or fried versions are available in some markets and have a less intense flavor.
Smoothies: Blend it with fruits and other ingredients to completely mask the texture and flavor while retaining many of the nutritional benefits.

Potential Risks and Considerations

While natto is a superfood for many, it is not suitable for everyone. As with any diet change, consulting a healthcare provider is recommended, particularly for individuals with pre-existing conditions.

Soy Allergies: Individuals with soy allergies should avoid natto, as it is made from fermented soybeans.
Blood Thinners: Due to its high vitamin K2 content and nattokinase, natto can interact with anticoagulant medications like warfarin. Medical supervision is necessary for those on such medication.
Digestive Issues: The high fiber and probiotic content can sometimes cause temporary gas or bloating, especially when first introduced to the diet. Starting with small portions can help your digestive system adjust.
Goitrogens: The soy in natto contains goitrogens, which may not be suitable for people with hypothyroidism, though fermentation can reduce their impact.

Conclusion

Scientific research continues to affirm the profound health benefits of natto, confirming its status as a powerhouse of nutrition and a valuable addition to a health-conscious diet. The potent combination of nattokinase for cardiovascular health, vitamin K2 for bone strength, and potent probiotics for gut health creates a synergistic effect that goes far beyond its simple soybean origins. While its strong flavor and unique texture may require an adventurous palate, the diverse ways to prepare and consume natto make it accessible to most. For those seeking to boost their intake of heart-healthy, bone-supporting, and gut-friendly compounds, incorporating this traditional Japanese superfood could be a very wise move. The evidence suggests that for many, the benefits of natto far outweigh the challenge of acquiring the taste. You can learn more about its specific enzyme, nattokinase, on the National Institutes of Health website.

Frequently Asked Questions

For beginners, mixing natto with rice is a great starting point. Try adding strong-flavored toppings like mustard, chopped green onions, or kimchi to help mask the unique taste and texture. Adding a little olive oil can also reduce the stringiness.

Natto is typically found in the refrigerated or frozen section of most Japanese or Asian supermarkets. In some Western countries, it may be available in the international food aisle of larger grocery stores.

No. Due to its exceptionally high vitamin K2 content and the blood-thinning effects of nattokinase, individuals on anticoagulant medication must consult a doctor before consuming natto. Changes in dosage or diet may be necessary.

You can cook with natto by adding it to things like fried rice or pasta, but cooking with high heat can destroy the live probiotic bacteria that are beneficial for gut health. For maximum probiotic benefit, it's best to consume it raw or add it to dishes after they've been cooked.

The sticky, stringy texture is caused by polyglutamic acid, which is produced during the fermentation process by the Bacillus subtilis bacteria. The pungent smell comes from various volatile compounds also generated by the bacteria.

Yes, research indicates natto is particularly beneficial for postmenopausal women. The high concentration of vitamin K2 (MK-7) has been linked to increased bone mineral density and a significant reduction in the rate of bone loss.

Yes. Manufacturers have developed 'dried natto' and 'fried natto' for those who find the traditional texture and smell too strong. While they are easier to eat, they may not offer the same probiotic benefits as fresh natto.