Nutrition Diet: Which vegetable has the most K2?

October 4, 2025 •

4 min read

According to the USDA, most vitamin K in American diets comes from the K1 found in plants, not the harder-to-find K2. So, which vegetable has the most K2? The surprising answer isn't a leafy green, but a fermented product, highlighting the critical role of bacterial fermentation in producing this key nutrient.

Quick Summary

While leafy greens contain vitamin K1, the richest source of vitamin K2 from a vegetable-based product is natto, a fermented soybean dish. Other fermented vegetables like sauerkraut also provide K2, which is essential for bone and heart health.

Key Points

Natto is the richest vegetable source: A fermented soybean product, natto, contains over 1,000 mcg of vitamin K2 per 100g, making it the most potent plant-based option.
Not all vitamin K is the same: Leafy green vegetables contain Vitamin K1 (phylloquinone), while K2 (menaquinone) is predominantly found in fermented foods and animal products.
Fermentation produces K2: The bacteria used to ferment foods like soybeans (natto) and cabbage (sauerkraut) are responsible for creating beneficial vitamin K2.
Sauerkraut contains K2: Fermented cabbage is a more accessible vegetable-based source of K2 than natto, though in much smaller, and variable, quantities.
Pair K1 with healthy fats: To improve the absorption of the K1 found in leafy greens, consume them alongside a source of fat, such as avocado or olive oil.
K2 supports bone and heart health: Unlike K1, K2 is specifically vital for regulating calcium metabolism, promoting bone density and preventing arterial calcification.

Understanding Vitamin K1 vs. K2

Before answering which vegetable has the most K2, it's crucial to understand the distinction between the two primary forms of vitamin K. Vitamin K1 (phylloquinone) is the most common form, found abundantly in leafy green vegetables like kale, spinach, and collard greens. Its primary function is in blood clotting.

Vitamin K2 (menaquinone) is less common in the average diet and is found in fermented foods and animal products. It has a longer half-life than K1 and plays a more significant role in regulating calcium metabolism. K2 directs calcium into bones and teeth while preventing it from accumulating in soft tissues like arteries and kidneys, a process known as calcification. Some gut bacteria can convert a small amount of K1 into K2, but this is often insufficient to meet optimal needs. Therefore, focusing on direct sources of K2 is essential for bone and cardiovascular health.

Natto: The Clear Winner for Vegetable-Derived K2

When it comes to vegetable-based sources, natto, a traditional Japanese dish made from fermented soybeans, stands far above the rest. This sticky, pungent dish is created by fermenting soybeans with the bacterium Bacillus subtilis natto, which produces exceptionally high levels of vitamin K2, specifically the MK-7 subtype.

Unrivaled K2 Content: A 100-gram serving of natto can contain over 1,000 mcg of vitamin K2 (MK-7), a significantly higher amount than any other plant-based food.
Health Benefits: The high MK-7 content is associated with a reduced risk of hip fractures in postmenopausal women. Studies also show that natto consumption can increase serum MK-7 levels effectively.
An Acquired Taste: While nutritionally dense, the strong flavor and sticky texture of natto can be an acquired taste for Western palates.

Fermented Cabbage: Sauerkraut as a K2 Source

Beyond natto, other fermented vegetable products can contribute a modest amount of K2 to your diet. Sauerkraut, made from fermented cabbage, is a more familiar option for many. The K2 in sauerkraut is produced by the bacteria during the fermentation process, though the amount is much lower and can vary depending on the specific bacterial strains and fermentation conditions. A half-cup of sauerkraut might contain around 2.75 to 6 mcg of K2. Opt for unpasteurized varieties with live and active cultures to maximize this benefit.

The Role of Leafy Greens and K1 Conversion

What about the leafy green vegetables so often touted for vitamin K? Greens like kale, spinach, collard greens, and broccoli are exceptional sources of vitamin K1. While K1 is important for blood clotting, its contribution to K2 levels via gut conversion is limited. To maximize the conversion and absorption of any form of vitamin K from leafy greens, it's beneficial to consume them with a healthy fat, such as olive oil or avocado, since vitamin K is fat-soluble.

Maximizing Your K2 Intake from Plant Sources

Here are some actionable steps to increase your intake of vitamin K2 from vegetable-based foods:

Embrace Natto: For a powerful and direct dose of MK-7, try incorporating natto into your diet. It can be mixed with rice or other foods to mellow its strong flavor.
Add Sauerkraut: Include a dollop of unpasteurized sauerkraut on sandwiches, salads, or alongside your main dish to get a probiotic boost and some K2.
Pair K1 with Fats: When eating K1-rich vegetables like kale or spinach, dress them with a vinaigrette or sauté them in a healthy oil to improve absorption.
Consider Making Your Own Ferments: Fermenting your own vegetables, such as cabbage for sauerkraut, can be a rewarding way to ensure a consistent supply of live-culture, K2-containing food.

A Comparison of Vegetable-Based Vitamin K Content


Food (per 100g)	Primary Vitamin K Type	Approximate Vitamin K2 Content (μg)	Notes
Natto (Fermented Soybeans)	K2 (MK-7)	~1,034.0	Richest source, requires fermentation with specific bacteria.
Sauerkraut (Fermented Cabbage)	K2 (Various MKs)	~4.8	K2 content varies based on fermentation method.
Spinach (Raw)	K1	~0.0	Contains high K1, minimal K2. Some K1 converted by gut bacteria.
Kale (Raw)	K1	~0.0	Contains high K1, minimal K2. Some K1 converted by gut bacteria.

Conclusion: Natto is the Leader

In the realm of plant-based foods, natto is the hands-down winner when it comes to vitamin K2 content. While other fermented vegetables like sauerkraut also offer K2, their contribution is far more modest. It's a common misconception that leafy greens are a good source of K2, when in fact they are rich in K1. A balanced nutrition diet should include a variety of these foods to ensure a broad spectrum of nutrients, and for a targeted boost of K2, fermented foods are your best bet. For further reading on the science behind vitamin K, consult authoritative sources like the National Institutes of Health Fact Sheet on Vitamin K.

Frequently Asked Questions

Kale is very high in vitamin K1, the type found in leafy green plants, but it contains virtually no vitamin K2. While the body can convert some K1 into K2, it is not an efficient process.

Yes, sauerkraut is a good source of vitamin K2, which is produced by the bacteria during fermentation. The amount can vary depending on the preparation method, but it is one of the better vegetable-based sources.

Vegans can get vitamin K2 from fermented vegetable products like natto and sauerkraut. While some K1 is converted by gut bacteria, relying solely on unfermented vegetables is unlikely to provide sufficient K2.

Vitamin K is a fat-soluble vitamin. You can improve its absorption by consuming K2-rich foods like natto or K1-rich vegetables like kale with a source of healthy fat, such as olive oil, nuts, or seeds.

Natto is exceptionally high in K2 because it is fermented with the specific bacterium Bacillus subtilis. This microorganism is known to produce large amounts of menaquinone-7 (MK-7), a potent form of K2.

Vitamin K2 is crucial for bone health, as it directs calcium to the bones and teeth. It also supports cardiovascular health by preventing calcium buildup in arteries.

Not all fermented vegetables are created equal regarding K2 content. The amount depends on the specific bacteria involved in the fermentation process. Natto is a standout due to its specific bacterial strain, while others like sauerkraut contain lesser amounts.