Which Japanese food has vitamin K?

December 22, 2025 •

4 min read

Natto, a traditional Japanese dish made from fermented soybeans, is widely recognized as the most potent dietary source of vitamin K2, offering several times the daily recommended intake in a single serving. However, many other Japanese foods contribute to this essential nutrient.

Quick Summary

This article explores the Japanese foods richest in vitamin K, from the fermented soybean superfood natto to nutrient-dense green vegetables, soy products, and seaweed.

Key Points

Natto's Vitamin K2: The fermented soybean dish natto is the richest known source of vitamin K2 (MK-7), a form highly beneficial for bone and heart health.
Leafy Green Sources: Common Japanese greens like spinach and komatsuna are excellent sources of vitamin K1 (phylloquinone), often prepared in side dishes.
Edamame Contribution: Immature soybeans, or edamame, provide a good source of vitamin K, along with protein and fiber, making them a healthy snack or side dish.
Seaweed Options: Seaweed varieties like nori and kelp, integral to Japanese cuisine, also contain vitamin K and other essential minerals.
Dietary Balance: A balanced Japanese diet incorporating fermented foods, greens, and seaweed naturally provides a comprehensive range of vitamin K types.

Natto: The Japanese Vitamin K2 Superfood

Natto is a traditional Japanese food created by fermenting soybeans with the bacterium Bacillus subtilis natto. This unique fermentation process produces exceptional levels of menaquinone-7 (MK-7), a highly bioavailable form of vitamin K2. While vitamin K1 is abundant in leafy greens, K2 (MK-7) is crucial for directing calcium to the bones and teeth and away from arteries, thus supporting both bone and cardiovascular health. Regular consumption of natto is a potential factor behind Japan's historically low rates of age-related bone and vascular issues.

Health Benefits of Natto's Vitamin K2

Beyond its role in blood clotting, the MK-7 in natto offers several advantages:

Bone Health: Activates proteins that help bind calcium to bone matrix, which is vital for maintaining bone mineral density.
Cardiovascular Health: Supports healthy blood vessel elasticity and reduces arterial calcification by guiding calcium away from soft tissues.
Neurological Health: Some research suggests a potential link between vitamin K2 and brain health, including supporting neurological functions and potentially mitigating cognitive decline.

Leafy Greens and Vegetables

Just like in Western diets, many leafy greens and cruciferous vegetables commonly used in Japanese cuisine are excellent sources of vitamin K, predominantly as vitamin K1 (phylloquinone). Some popular options include:

Spinach (ほうれん草 - hōrensō): A versatile leafy green rich in vitamin K, often served blanched and mixed with a sesame dressing (goma-ae) or in soups.
Komatsuna (小松菜): Also known as Japanese mustard spinach, komatsuna is packed with nutrients, including vitamin K. It can be prepared in stir-fries, pickled, or added to miso soup.
Kale (ケール - kēru): While less traditional than spinach, kale is used in some modern Japanese dishes and contains a significant amount of vitamin K1.

Edamame and Other Soy Products

Immature soybeans, or edamame, are a popular snack and side dish in Japan and a good source of vitamin K1. A single cup of cooked edamame provides a notable percentage of the daily value for vitamin K, along with protein, fiber, and other essential nutrients. Other soy products also contain vitamin K, including:

Tofu: While the content is lower than in fermented products, tofu still contributes to vitamin K intake.
Roasted Soybeans: A nutritious snack that offers a modest amount of vitamin K.

Seaweed Varieties

Seaweed is a staple in the Japanese diet and some varieties contain vitamin K, especially kelp and nori.

Kelp (kombu): Used to make dashi (soup stock), kelp contains vitamin K and is also rich in iodine and other minerals.
Nori (海苔): The dried seaweed sheets used for sushi rolls contain vitamin K, iron, and protein.

Comparison: Vitamin K in Japanese Foods


Food Item	Primary Vitamin K Form	Vitamin K Amount (per serving)	Key Characteristics & Notes
Natto	K2 (Menaquinone-7)	~850 mcg per 3 oz (½ cup)	Highest source of bioavailable K2; acquired taste due to sticky texture.
Edamame	K1 (Phylloquinone)	~41 mcg per cup, cooked	Excellent snack; also high in protein and fiber.
Spinach	K1 (Phylloquinone)	~145 mcg per cup, raw	Versatile leafy green used in many dishes.
Kelp (Kombu)	K1 (Phylloquinone)	~66 mcg per serving	Used primarily for broth (dashi); rich in iodine.

Incorporating Japanese Vitamin K Sources into Your Diet

For a balanced intake of vitamin K, consider adding a variety of Japanese foods to your meals. The traditional Japanese diet, which naturally incorporates these foods, has long been associated with good vascular and bone health.

Creative Ways to Enjoy Natto

If the strong taste and unique texture of natto are a challenge, try these methods to make it more palatable:

Mix with Rice: The most common way to eat natto is over a bowl of hot rice, often with a raw egg and soy sauce.
Add Condiments: Mixing in Japanese mustard (karashi), green onions, or even a bit of chili oil can help balance the flavor.
Incorporate into Other Dishes: Natto can be added to soups, salads, or even mixed into fried rice to distribute its flavor and stickiness.

Other Simple Tips for Boosting Vitamin K

Use kombu to make a flavorful dashi stock for miso soup or noodle dishes, subtly adding nutrients.
Sprinkle toasted nori flakes over rice, noodles, or salads for a boost of flavor and vitamin K.
Incorporate blanched spinach or komatsuna into side dishes (ohitashi), dressed with a sesame-soy sauce dressing.

Conclusion

While the fermented soybean dish natto is the most concentrated Japanese source of the highly bioavailable vitamin K2, other foods like edamame, spinach, and kelp provide valuable amounts of vitamin K1. By embracing the diversity of the Japanese diet, you can easily incorporate a wide spectrum of this essential nutrient to support bone and heart health. Whether you choose the potent MK-7 from natto or the K1 from fresh greens, traditional Japanese cuisine offers many delicious and healthy options.

For more detailed nutritional information, consult the National Institutes of Health Fact Sheet on Vitamin K.

Frequently Asked Questions

Vitamin K1 (phylloquinone) is found primarily in leafy green vegetables, while vitamin K2 (menaquinone) is produced by bacteria and found in fermented foods like natto and some animal products. K2 has a longer half-life and is more effective at activating certain proteins crucial for bone and heart health.

Natto has a distinct and strong flavor profile, described as earthy and nutty, with a sticky, slimy texture. It is often considered an acquired taste, and many people mix it with condiments like soy sauce or mustard to enhance the flavor.

Yes, you can. While natto is an exceptional source of K2, you can obtain sufficient vitamin K from other Japanese foods like spinach, komatsuna, edamame, and seaweed (K1), as well as a variety of other fermented and animal products.

Yes, certain seaweeds like kelp (kombu) and nori do contain vitamin K. While the concentration may not be as high as in natto, seaweed contributes to overall intake and offers a range of other nutrients.

Vitamin K is relatively stable under heat. To retain nutrients and texture, greens like spinach and komatsuna are often briefly blanched or quickly stir-fried in Japanese cooking, as seen in dishes like ohitashi.

While natto is the standout, other fermented products, including certain types of miso, may contain varying amounts of vitamin K2 depending on the fermentation process and bacterial strains used.

If you are on blood-thinning medication like warfarin, it is crucial to consult your doctor before significantly increasing your intake of vitamin K-rich foods, as vitamin K plays a role in blood clotting and can affect medication effectiveness.