Is natto good for you? Exploring the health benefits of this Japanese superfood

December 13, 2025 •

4 min read

According to a 2020 announcement by the National Cancer Center in Japan, high consumption of natto lowers mortality risk. But beyond this impressive finding, is natto good for you and what makes it such a powerful addition to your diet? This fermented soybean dish offers a surprising array of nutritional advantages.

Quick Summary

Natto is a traditional Japanese food made from fermented soybeans, packed with potent nutrients like probiotics, Vitamin K2, and nattokinase, supporting heart, bone, and gut health.

Key Points

Heart Health: Natto contains nattokinase, an enzyme that acts as a natural blood thinner, helping to dissolve blood clots and improve circulation.
Bone Strength: As the richest food source of Vitamin K2, natto helps properly regulate calcium, preventing bone density loss and arterial calcification.
Gut Friendly: The Bacillus subtilis probiotics in natto support a healthy gut microbiome, improving digestion and enhancing nutrient absorption.
Immune Booster: A strong gut biome, combined with a high content of vitamins like C and minerals like zinc, helps strengthen the body's immune response.
Nutrient-Dense: Natto is a potent source of plant-based protein, dietary fiber, iron, and manganese, making it a very nutritious food.
Potential Risks: Individuals on blood-thinning medication or those with a soy allergy should be cautious, as natto's high Vitamin K2 content can interfere with certain drugs.

What is Natto?

Natto is a traditional Japanese dish made from cooked soybeans fermented with a special bacterium, Bacillus subtilis var. natto. This fermentation process results in a product with a sticky, stringy, and slimy texture, along with a powerful, pungent aroma that many liken to ammonia. While its taste and texture can be an acquired taste for some, natto has been a dietary staple in Japan for centuries, particularly in the eastern regions where it is often enjoyed at breakfast over rice. The fermentation not only creates its unique characteristics but also produces beneficial compounds that enhance its nutritional value and therapeutic potential.

The Unique Nutritional Profile

Natto is a nutritional powerhouse, especially considering its small serving size. A typical 50-gram serving (about 1.8 ounces) provides a balanced mix of macronutrients and is an exceptional source of several key vitamins and minerals.

Protein: As a soybean product, natto is a high-quality, plant-based source of protein, containing all nine essential amino acids. This makes it an excellent option for vegetarians and vegans looking to increase their protein intake.
Fiber: Natto is rich in dietary fiber, which is crucial for digestive health, helping to regulate blood sugar levels and promote bowel regularity.
Vitamins: It is the richest food source of Vitamin K2 (specifically menaquinone-7 or MK-7), a nutrient critical for bone and cardiovascular health. It also contains Vitamin C, B vitamins (including B2 and B6), and folate.
Minerals: A single serving is an impressive source of manganese and iron. It also provides significant amounts of calcium, magnesium, and potassium.
Probiotics: The fermentation with Bacillus subtilis natto introduces live microorganisms (probiotics) that are beneficial for gut health.
Nattokinase: The bacteria produce a potent enzyme called nattokinase during fermentation, which has been extensively studied for its powerful effects on cardiovascular health.

Significant Health Benefits

Supporting Heart and Cardiovascular Health

One of the most well-documented benefits of natto is its positive impact on the cardiovascular system.

Blood Clot Prevention: The enzyme nattokinase acts as a potent natural blood thinner by directly degrading fibrin, a protein involved in blood clot formation. Regular consumption has been associated with enhanced fibrinolytic activity, which can help prevent blood clots and reduce the risk of heart attack and stroke.
Blood Pressure Regulation: Research has shown that nattokinase supplementation can help lower blood pressure in individuals with hypertension.
Cholesterol Management: The fiber and polyunsaturated fats in natto can help reduce LDL (“bad”) cholesterol levels, contributing to a healthier lipid profile.

Strengthening Bones

Natto is a champion for bone health, largely due to its unparalleled concentration of Vitamin K2.

Calcium Regulation: Vitamin K2 activates proteins that ensure calcium is directed to the bones, where it is needed, and away from the arteries, where it could cause calcification.
Reduced Bone Loss: Multiple Japanese studies have demonstrated that regular natto consumption is linked to a reduced rate of bone mineral density (BMD) loss, particularly in postmenopausal women who are at a higher risk for osteoporosis.

Promoting Gut and Digestive Health

As a fermented food, natto is a boon for the digestive system.

Probiotic Powerhouse: The live Bacillus subtilis natto bacteria survive the journey through the digestive tract, where they help balance the gut microbiome.
Enhanced Digestion: The fermentation process breaks down anti-nutrients found in soybeans, making the protein and other nutrients more digestible and absorbable. The dietary fiber also promotes regularity and helps prevent constipation.

Boosting Immune Function

A healthy gut is a cornerstone of a strong immune system, and natto plays a key role.

Supports Gut-Immune Axis: The probiotics in natto contribute to a healthy and diverse gut microbiome, which is essential for immune system function.
Rich in Immune-Supporting Nutrients: Natto is packed with vitamins and minerals like Vitamin C, iron, and zinc, all of which are vital for a healthy immune response.

Natto vs. Other Fermented Foods

To understand natto's distinct advantages, a comparison with other popular fermented foods is useful.


Feature	Natto	Yogurt	Kimchi
Base Ingredient	Soybeans	Milk	Cabbage, other vegetables
Key Probiotic	Bacillus subtilis	Lactobacillus, Bifidobacterium	Lactobacillus
Vitamin K2 Content	Extremely High	Moderate (dependent on type)	Low
Nattokinase	Yes	No	No
Fiber Content	High	Low	High
Protein Source	Plant-based, complete	Animal-based, complete	Plant-based
Common Risks	High K2 (blood thinners), soy allergy	Lactose intolerance, dairy allergy	High sodium content

Potential Risks and Considerations

While largely beneficial, natto isn't for everyone. It's important to be aware of the potential risks.

Blood-Thinning Medication: Due to its very high Vitamin K2 content and the presence of nattokinase, natto can interfere with anticoagulant drugs like warfarin. Anyone on blood-thinning medication should consult their doctor before adding significant amounts of natto to their diet.
Soy Allergy: As a product of soybeans, it is unsuitable for anyone with a soy allergy or intolerance.
Thyroid Function: Soy is considered a goitrogen, which can interfere with thyroid function in individuals with an already impaired thyroid. Healthy individuals are unlikely to be affected, but caution is advised for those with hypothyroidism.

Conclusion

Is natto good for you? The scientific evidence overwhelmingly suggests that it is, earning its reputation as a superfood. From supporting heart and bone health with its unique Vitamin K2 and nattokinase content to boosting gut and immune function with probiotics and fiber, natto is a remarkably nutritious food. While its characteristic smell and sticky texture can be a hurdle for some, the benefits are substantial and have been enjoyed in Japan for centuries. For those without contraindications, incorporating this nutrient-dense fermented food into your diet is a simple and effective way to promote overall well-being. For more in-depth clinical information on nattokinase, refer to authoritative scientific reviews.

Frequently Asked Questions

Natto has a strong, pungent odor often likened to ammonia, and a savory, earthy, and sometimes slightly bitter or cheesy taste. Its texture is uniquely sticky, stringy, and slimy, a result of the fermentation process.

Natto is traditionally mixed vigorously and served over warm rice. To mask the texture, you can add mustard, soy sauce, or green onions. For a more subtle approach, blend it into smoothies or incorporate it into pasta sauces or curries.

While nattokinase is available in supplement form and has shown promise, eating whole natto provides the full spectrum of nutrients, including probiotics, Vitamin K2, and fiber. The synergistic effects of these components may be greater than from a single isolated supplement.

Yes, natto is an excellent food for vegans and vegetarians. It is a complete plant-based protein source, rich in iron, calcium, and Vitamin K2, a nutrient often more abundant in animal products.

Unlike miso or tofu, natto is fermented with a specific bacterium (Bacillus subtilis var. natto) over a short period, which produces nattokinase and the high concentration of Vitamin K2. The fermentation process for miso is longer and uses mold, resulting in a paste rather than sticky beans.

Yes, store-bought natto can often be frozen. Manufacturers sometimes freeze it for distribution, and it can be thawed before consumption. Freezing and thawing can slightly alter the texture, but it remains a viable way to preserve it.

Some people may experience mild digestive issues like gas or bloating due to the high fiber content, especially when first adding it to their diet. This often subsides as the digestive system adjusts. For most people, it is well-tolerated and safe.