What veggie has vitamin K2? The surprising truth about fermented foods

January 7, 2026 •

4 min read

While many people believe leafy greens are a primary source of all Vitamin K, studies confirm that these vegetables mostly contain Vitamin K1. The most potent and well-known plant-based source of Vitamin K2 is, in fact, the Japanese fermented soybean product known as natto.

Quick Summary

The richest vegetarian source of vitamin K2 is natto, a fermented soybean dish, with other fermented vegetables like sauerkraut also contributing smaller amounts. Most vegetables, especially leafy greens like kale and spinach, are high in vitamin K1, not K2, which is produced by bacteria.

Key Points

Natto is the primary veggie source: The Japanese dish of fermented soybeans is overwhelmingly the richest plant-based source of vitamin K2 (MK-7).
Leafy greens contain K1, not K2: Vegetables like kale and spinach are rich in Vitamin K1, which differs in function and absorption from Vitamin K2.
K2 is a product of fermentation: Vitamin K2 is mainly produced by bacteria, meaning fermented foods are the most reliable plant-based source.
Gut bacteria play a role: The bacteria in your large intestine can produce some K2 from K1, though absorption efficiency is limited.
K2 is crucial for bone and heart health: Unlike K1, K2 activates proteins that guide calcium to bones and away from arteries, supporting cardiovascular and skeletal health.
Healthy fats aid absorption: Since Vitamin K is fat-soluble, consuming K1 and K2-rich foods with healthy fats enhances their bioavailability.

Understanding the Two Forms of Vitamin K

Vitamin K is a fat-soluble nutrient essential for several bodily functions, most notably for blood clotting and bone health. However, it is crucial to distinguish between its two main forms: Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinones). These two forms differ significantly in their dietary sources, chemical structure, and metabolic roles in the body.

Vitamin K1 is predominantly found in green leafy vegetables, where it plays a key role in the plant's photosynthesis. When humans consume these plants, K1 is primarily used by the liver for the synthesis of blood-clotting proteins. In contrast, Vitamin K2 is mostly synthesized by bacteria and is more involved in regulating where calcium ends up in the body, directing it to bones and teeth while preventing it from accumulating in soft tissues like arteries.

Natto: The Powerhouse Plant Source of K2

For those seeking a powerful and natural vegetable source of Vitamin K2, the Japanese delicacy natto is the clear winner. Made from soybeans fermented with Bacillus subtilis bacteria, natto is exceptionally rich in the long-chain menaquinone-7 (MK-7) form of Vitamin K2. One small serving of natto can provide a massive amount of K2, far exceeding the daily requirement and surpassing any other plant-based food source by a significant margin. Despite its sticky texture and pungent flavor, which can be an acquired taste, its nutritional benefits make it a prized health food in Japan.

Other fermented vegetables

While natto holds the top spot, other fermented vegetable products can also contribute to your K2 intake. Sauerkraut, made from fermented cabbage, contains small amounts of K2 produced by the fermenting bacteria. However, the K2 concentration in sauerkraut is significantly lower than in natto, so it cannot be relied upon as a primary source. Nonetheless, incorporating a variety of fermented foods, which also offer probiotic benefits, is a smart dietary choice.

K1-Rich Vegetables vs. K2-Rich Fermented Foods

It's a common misunderstanding that all Vitamin K comes from leafy greens, which leads many to overlook the crucial role of K2. The reality is that green vegetables provide K1, while K2 primarily comes from bacterial sources.

Comparison of Common Vegetable Sources


Food Source	Primary Vitamin K Form	Richness for K2	How to Incorporate
Natto (Fermented Soybeans)	Vitamin K2 (MK-7)	Highest	Mixed with rice, savory dishes, or in soups.
Sauerkraut (Fermented Cabbage)	Vitamin K2 (low), K1	Low	Toppings for sandwiches, salads, or as a side dish.
Kale, Spinach, Broccoli	Vitamin K1	Negligible	Salads, stir-fries, smoothies, and cooked dishes.
Brussels Sprouts, Collard Greens	Vitamin K1	Negligible	Roasted, steamed, or sauteed as a side.
Avocado	Vitamin K1	Negligible	Added to salads, toast, or smoothies.

The Role of Gut Bacteria

Interestingly, the bacteria residing in the human gut can also convert some of the Vitamin K1 consumed from plants into Vitamin K2. However, the efficiency and extent of this conversion can vary between individuals, and much of the K2 produced this way is synthesized in the large intestine, where its absorption is less efficient. This makes dietary intake of K2, especially from highly potent sources like natto, a more reliable way to boost your levels. Ensuring good gut health through a diet rich in prebiotics and probiotics can also indirectly support this internal production pathway.

Maximizing Vitamin K Absorption

Since Vitamin K is a fat-soluble vitamin, its absorption is enhanced when consumed with a source of dietary fat. For your K1-rich leafy green salads, adding a simple olive oil dressing or some avocado can help your body get the most out of the nutrients. Similarly, pairing fermented vegetables with healthy fats, like adding sauerkraut to a sandwich with a smear of vegan mayonnaise or avocado, is a good strategy.

Conclusion

To answer the question, "What veggie has vitamin K2?", the most accurate response is fermented soybeans, or natto. While many vegetables are high in Vitamin K1, they are not reliable sources of K2. For those following a plant-based diet, incorporating natto is the most effective way to ensure a robust intake of K2. Alternatively, other fermented vegetables like sauerkraut can contribute, though in much smaller quantities. Understanding the distinction between K1 and K2 and including a diverse range of plant-based foods, especially fermented options, is key to maintaining optimal Vitamin K levels for both bone and heart health. For a comprehensive guide to plant-based nutrition, you can consult a resource like VeganHealth.org.

How Vitamin K1 and K2 Work Differently

While K1 is vital for blood clotting, K2's main role is to activate proteins that direct calcium to the right places. This helps build strong bones and prevents calcium accumulation in arteries, supporting cardiovascular health.

The K2 Absorption Advantage

Due to its longer-chain chemical structure, Vitamin K2 is absorbed more slowly and remains in the body for a longer duration compared to K1, allowing it to perform its functions more effectively.

Beyond Natto: A Diverse Approach

While natto is the king of plant-based K2, a balanced diet including a variety of fermented and non-fermented vegetables is beneficial for overall nutrient intake and gut health.

Gut Health Matters

Supporting your gut microbiome with fermented foods and probiotics can aid your body's natural production of K2, supplementing your dietary intake.

Frequently Asked Questions

No, kale is an excellent source of Vitamin K1 (phylloquinone), but contains negligible amounts of Vitamin K2 (menaquinone). The richest vegetable source of K2 is natto, a fermented soybean product.

Vitamin K1 is mainly found in leafy greens and is used by the liver for blood clotting. Vitamin K2 is primarily bacterial in origin, found in fermented foods, and directs calcium to bones while preventing arterial calcification.

Yes, vegans can get K2 primarily from fermented soy products like natto. The body also converts some K1 into K2, but relying on dietary K2 from sources like natto is a more effective strategy.

Natto is a traditional Japanese food made from fermented soybeans. It has a sticky, stringy texture and a strong, savory flavor. It is prized for being the richest food source of Vitamin K2 (MK-7).

Yes, sauerkraut, which is fermented cabbage, contains small amounts of Vitamin K2 due to the bacterial fermentation process. However, its K2 content is far lower than that found in natto.

Yes, bacteria in the human large intestine can synthesize Vitamin K2. However, the amount produced and absorbed varies, so dietary intake from fermented foods is still important for reliable levels.

Vitamin K2 activates a protein called osteocalcin, which helps bind calcium to the bone matrix, improving bone density and strength. This process is crucial for preventing osteoporosis.

Cooking leafy greens high in Vitamin K1 can sometimes increase the concentration of the vitamin by reducing water content. For example, a cup of cooked spinach has more Vitamin K than a cup of raw spinach.

It is generally better to get vitamins from whole foods whenever possible. A balanced diet including both K1-rich leafy greens and fermented K2 sources like natto is the ideal approach.