What happens if I eat natto every day? Exploring the daily diet impact

November 1, 2025 •

4 min read

In 2020, Japan's National Cancer Center reported that high natto consumption lowers mortality risk. This traditional, fermented soybean dish, with its unique sticky texture and pungent flavor, is a staple in many Japanese diets, leading many to ask: What happens if I eat natto every day? The answer lies in its rich profile of unique nutrients and potent compounds.

Quick Summary

Daily natto consumption can offer significant benefits for heart, bone, and gut health due to its high levels of nattokinase, vitamin K2, and probiotics. However, caution is advised for individuals on blood thinners, those with soy allergies, or thyroid conditions due to potential risks.

Key Points

Heart Health Boost: Daily natto consumption provides nattokinase and Vitamin K2, which support healthy blood flow and reduce the risk of blood clots and arterial calcification.
Enhanced Bone Density: Natto is a potent source of Vitamin K2, which is critical for directing calcium to the bones and helping to prevent osteoporosis.
Superior Gut Health: The probiotics from Bacillus subtilis in natto promote a balanced and diverse gut microbiome, aiding digestion and boosting the immune system.
Blood Thinner Interaction: Individuals taking anticoagulant medications like warfarin should consult a doctor, as natto's high vitamin K2 content and nattokinase can interfere with their effects.
Moderation is Key: While a daily 40-50 gram serving is generally safe and beneficial for healthy individuals, those new to natto should start with smaller portions to avoid potential digestive issues.

The Nutritional Powerhouse: What's in Natto?

Natto is made by fermenting soybeans with the Bacillus subtilis bacteria, transforming the humble bean into a nutrient-dense superfood. This fermentation process not only makes the soybeans more digestible but also creates unique compounds and supercharges the content of existing vitamins and minerals.

Probiotics: Natto is a rich source of Bacillus subtilis probiotics, which can survive the harsh stomach environment to colonize the gut. These beneficial bacteria promote a healthy gut microbiome, aid digestion, and may alleviate issues like gas, bloating, and constipation.
Vitamin K2 (MK-7): Natto is one of the highest food sources of vitamin K2, a crucial nutrient for bone and cardiovascular health. It directs calcium to the bones, preventing its accumulation in arteries where it can cause hardening.
Nattokinase: This potent enzyme, produced during fermentation, is known for its blood-thinning properties. It can dissolve fibrin, a protein involved in blood clotting, which may support healthy blood flow and reduce the risk of heart disease.
Protein and Fiber: A single serving of natto is a complete plant-based protein source and is rich in dietary fiber, promoting satiety and supporting digestive health.

Daily Natto: The Potential Benefits

For those who tolerate its distinct flavor and texture, incorporating natto daily into a balanced diet can yield impressive health rewards over time.

Enhanced Gut Health

Consistent intake of natto provides a steady supply of Bacillus subtilis probiotics to the gut. This can lead to a more balanced and diverse gut microbiota, which is linked to everything from better digestion and nutrient absorption to improved mood and reduced inflammation. A healthy gut microbiome is also a cornerstone of a robust immune system.

Better Heart Health

Eating natto regularly means consistently supplying your body with nattokinase and vitamin K2, two compounds vital for cardiovascular health. Nattokinase's fibrin-dissolving action can help keep blood clots from forming, while vitamin K2's ability to regulate calcium helps maintain arterial flexibility. Together, these effects may help lower blood pressure and cholesterol levels, reducing the overall risk of heart disease.

Stronger Bones

The exceptionally high concentration of vitamin K2 in natto plays a critical role in bone mineral density. Studies have shown that regular natto consumption is linked to a lower risk of bone fractures, particularly in postmenopausal women who are at increased risk of osteoporosis.

Boosted Immunity

A healthy gut is intrinsically linked to a healthy immune system. By fostering a thriving gut microbiome, the probiotics in natto bolster the body's defenses. Additionally, natto's rich vitamin C, zinc, and selenium content further support immune function.

Other Potential Benefits

Beyond the core benefits, daily natto may also contribute to brain health by potentially reducing inflammation and aiding circulation. Its high protein and fiber content also promote satiety, which can assist in weight management by helping you feel full for longer.

Potential Risks and Considerations of Eating Natto Daily

While beneficial for most, a daily dose of natto isn't suitable for everyone and requires moderation. It's crucial to be aware of the potential risks.

Blood-Thinning Medications

Warning: Individuals on blood-thinning medications, such as warfarin, must consult a doctor before consuming natto regularly. The high vitamin K2 content can interfere with these medications and cause adverse effects. The nattokinase enzyme also has anticoagulant properties, which could compound this issue.

Hypothyroidism

Soy is considered a goitrogen, which means it can interfere with the thyroid gland's function, especially in individuals with an existing thyroid disorder. Those with hypothyroidism may need to limit their intake or consult a healthcare provider.

Gastrointestinal Issues

For those unaccustomed to fermented foods or high fiber, starting with a daily serving of natto can cause temporary gastrointestinal discomfort, such as gas or bloating. It is best to start with small portions and gradually increase them.

Allergic Reactions

As natto is a soy product, people with soy allergies should avoid it entirely. Allergic reactions can include hives, swelling, or breathing difficulties.

How to Safely Incorporate Natto into a Daily Diet

If you are healthy and not on contraindicating medication, adding natto to your daily routine can be a great idea. A recommended daily serving is typically one 40-50 gram pack.

Start with small amounts to let your digestive system adjust.
Mix with other foods to temper the strong flavor, such as soy sauce, mustard, chives, kimchi, or a raw egg.
For those who dislike the texture, stir it into miso soup or a savory rice bowl, where the stickiness is less pronounced.
Try incorporating it into breakfast with rice or toast, or as part of a nutritious lunch or dinner bowl.

Natto vs. Other Fermented Soy Products

While natto shares a heritage with other fermented soy products, its unique fermentation process gives it a distinct nutritional profile. Here’s how it compares:


Feature	Natto	Miso	Tempeh
Fermentation Agent	Bacillus subtilis	Aspergillus oryzae (Koji)	Rhizopus oligosporus
Physical Form	Whole, sticky, stringy beans	Paste	Firm cake
Key Enzyme	Nattokinase	Varied digestive enzymes	None
Rich in Vitamin K2?	Highest food source (MK-7)	Contains some, but lower	Contains some, but lower
Primary Probiotic	Bacillus subtilis	Varied, often cultured later	Rhizopus mold
Flavor Profile	Pungent, ammonia-like, strong	Salty, umami-rich, varied	Nutty, earthy

Conclusion: Is Daily Natto Right for You?

For most healthy individuals, adding a single serving of natto to a daily diet can be an excellent way to boost heart health, strengthen bones, and improve digestive function. Its impressive profile of nattokinase, probiotics, and vitamin K2 is a powerful combination for long-term wellness. However, it is essential to be mindful of its potent effects and consult a healthcare professional if you have pre-existing conditions like hypothyroidism or take blood-thinning medication. By starting with small portions and listening to your body, you can safely enjoy the benefits of this remarkable Japanese superfood as part of a balanced nutritional diet. You can learn more about its specific nutrient content and potential benefits through research from institutions like the National Institutes of Health.

Frequently Asked Questions

A standard serving of one 40-50 gram pack per day is generally recommended for healthy individuals. It's best to start with smaller portions if you are new to natto to allow your body to adjust.

For most, side effects are minimal, but some may experience temporary gas or bloating due to the high fiber and probiotic content. Individuals on blood thinners or with thyroid issues face more serious risks and should consult a doctor.

The nattokinase enzyme in natto has been shown to lower blood pressure. A daily intake can have a consistent blood-pressure-lowering effect, though it should not replace prescribed medication.

While the probiotics may be affected by high heat, the heat-stable nattokinase and vitamin K2 remain. Adding natto to warm dishes like soups or rice is a common practice and retains many of its benefits.

Eating it raw or with warm rice is the traditional method. Mixing it with a little soy sauce, mustard, or other condiments can improve the taste. A daily dose ensures a consistent supply of its beneficial compounds.

Individuals on blood-thinning medications, those with soy allergies, and people with certain thyroid conditions should avoid or limit natto, and always consult a doctor.

Yes, natto has a distinctive and pungent smell, often compared to aged cheese. It also has a sticky, stringy texture. The taste and texture are an acquired taste for many.