What is a vegan source of K2? The Ultimate Guide

October 30, 2025 •

4 min read

Natto, a traditional Japanese fermented food, is by far the richest natural vegan source of vitamin K2, also known as menaquinone. Understanding this unique food is crucial for vegans, as K2 is most commonly found in animal products and plays a vital role in bone and cardiovascular health.

Quick Summary

The richest vegan source of vitamin K2 is natto, a fermented soy product, due to the bacteria used in its creation. Other fermented plant foods offer lower concentrations. The body can also convert some K1 from leafy greens into K2. High-quality vegan supplements are a reliable way to ensure adequate intake.

Key Points

Natto is King: The Japanese fermented soybean dish, natto, is the most concentrated vegan food source of vitamin K2, specifically the highly bioavailable MK-7 variant.
Other Fermented Foods: While less potent than natto, other fermented plant-based foods like sauerkraut and tempeh provide smaller, though potentially beneficial, amounts of vitamin K2.
Gut Bacteria Conversion: A healthy gut microbiome can convert some vitamin K1 from leafy greens into K2, but this process is variable and may not be a sufficient sole source.
Vegan Supplements: High-quality vegan K2 supplements, typically containing MK-7, are a convenient and reliable way to ensure consistent intake.
Consume with Fat: Since K2 is fat-soluble, absorption is enhanced when consumed with a source of healthy fat, such as avocado or olive oil.
Synergy with Vitamin D: K2 works in partnership with vitamin D3 to support bone and heart health, so ensuring adequate intake of both is important.

What is Vitamin K and Why is K2 Important?

Vitamin K is a fat-soluble vitamin essential for various bodily functions. It comes in two primary forms: K1 (phylloquinone) and K2 (menaquinone). Vitamin K1 is abundant in plant foods, especially green leafy vegetables, and is most known for its role in blood clotting. Vitamin K2, however, is a different story. It is predominantly found in animal products and fermented foods and plays a unique role in calcium metabolism, directing it to the bones and teeth and away from arteries and soft tissues. For those on a plant-based diet, identifying a vegan source of K2 is particularly important for bone and cardiovascular health.

Natto: The Unrivaled Vegan K2 Source

The search for a significant vegan source of K2 begins and often ends with natto. This traditional Japanese food consists of soybeans fermented with the Bacillus subtilis natto bacteria. It is during this fermentation process that a potent form of K2, specifically menaquinone-7 (MK-7), is produced. A single tablespoon of natto can contain more than enough K2 to meet daily needs, making it an incredibly concentrated source. While its strong flavor and slimy texture can be an acquired taste for some, its nutritional benefits are undeniable.

Other Fermented Vegan Foods

Natto is not the only source of K2 among fermented plant foods, but others contain significantly lower amounts. The K2 content in these foods depends on the specific bacteria used in fermentation.

Sauerkraut: Fermented cabbage can contain a small amount of K2, though much less than natto. Its production and bacterial cultures determine the final K2 levels.
Tempeh: This fermented soybean product, a staple in Indonesian cuisine, may contain some K2 but is not a significant source.
Kombucha: While a probiotic-rich beverage, kombucha provides only a minimal amount of K2.

The Role of Gut Bacteria and K1 Conversion

Our intestinal bacteria play a role in synthesizing K2 from the K1 we consume. As long as an individual has a healthy and balanced gut microbiome, along with adequate intake of K1 from leafy greens, this process can provide a modest amount of K2. However, factors like antibiotic use or gut health issues can disrupt this process. While this internal conversion helps, relying on it alone may not be sufficient to achieve optimal K2 levels, especially for those concerned with bone or cardiovascular health.

Vegan K2 Supplements

For many vegans, food sources may not be practical or sufficient, which is where supplements come in. High-quality vegan K2 supplements, often derived from fermented chickpeas or natto extracts, provide a convenient and reliable way to ensure adequate intake. These supplements typically feature the MK-7 form of K2, which has a longer half-life and better bioavailability than other forms. Combining a vegan K2 supplement with a vegan D3 supplement is a common practice, as these two fat-soluble vitamins work synergistically to support bone health.

A Comparison of Vegan K2 Sources


Source	Vitamin K2 (Menaquinone) Content	Main MK-7 Form	Pros	Cons
Natto	Very High (~1000 mcg/100g)	Yes, abundant	Highest food source, whole food, probiotic benefits	Acquired taste, sticky texture, may be hard to find
Sauerkraut	Very Low (~2.75 mcg/half-cup)	Yes, but minimal	Probiotic benefits, more common food	Low K2 concentration, inconsistent levels
Gut Bacteria	Variable	Yes, but variable	Internal production from K1	Dependent on gut health, unpredictable output
Vegan Supplements	Highly standardized	Yes, typically high-bioavailability MK-7	Guaranteed dose, convenient, tasteless	Not a whole food, potential for unnecessary additives

How to Maximize K2 Absorption from Food

Because vitamin K is fat-soluble, consuming it with a source of healthy fat enhances absorption. When eating foods high in K1 (which can be converted to K2) or a food like natto, consider pairing them with a source of fat such as:

Avocado
Nuts or seeds
Olive oil or canola oil

This simple addition can make a noticeable difference in how much vitamin K your body utilizes. For more comprehensive information on healthy vegan diets, visit The Vegan Society.

Conclusion

While vitamin K1 is abundant in plant foods, a dedicated approach is necessary to secure adequate vitamin K2 on a vegan diet. Natto is the standout, natural food source of K2, offering a potent dose in one serving. For those who cannot or will not consume natto, other fermented foods provide small amounts, but relying solely on them may not be sufficient. Therefore, a high-quality vegan K2 supplement is often the most practical and reliable way to ensure optimal intake. By understanding the distinct roles of K1 and K2 and incorporating these strategies, vegans can confidently support their bone and cardiovascular health. It's always wise to consult a healthcare provider or a registered dietitian if you have concerns about your nutritional intake, especially when considering supplementation.

Frequently Asked Questions

Vitamin K1 (phylloquinone) is found mainly in leafy green vegetables and is crucial for blood clotting. Vitamin K2 (menaquinone) is produced by bacteria, found in fermented foods and animal products, and primarily functions in calcium regulation for bone and cardiovascular health.

No. While leafy greens are rich in vitamin K1, they contain very little, if any, preformed K2. The body can convert some K1 to K2 with the help of gut bacteria, but this is a less reliable and potent source than food-based K2 like natto.

Natto is the richest and most concentrated vegan food source of K2 by a large margin. Other fermented plant foods like sauerkraut and tempeh do contain smaller amounts, but they are not considered significant sources.

If natto is not palatable, the most reliable alternatives are high-quality vegan K2 supplements, typically derived from fermented chickpeas or soy. Some people may also increase their intake of K1-rich foods and support gut health to maximize internal K2 conversion, though this is less predictable.

Given that K2 is scarce in most Western vegan diets, and its distinct role in calcium metabolism, many health experts and nutritionists recommend vegan K2 supplementation, particularly if relying on food sources isn't practical.

Vitamins K2 and D3 work together. Vitamin D3 facilitates the absorption of calcium, while vitamin K2 activates proteins that ensure this calcium is deposited correctly into bones and teeth, rather than accumulating in arteries and soft tissues.

The K2 content varies, but natto contains an astonishingly high amount, around 1000 mcg per 100g, while sauerkraut has a much lower concentration, approximately 2.75 mcg per half-cup.

MK-4 is a short-chain form found in animal products and created from K1 in the body. MK-7 is a long-chain form, produced during fermentation (like in natto), and is known for its higher bioavailability and longer half-life in the bloodstream.