Understanding Nutrition: What are the main sources of vitamin K?

October 14, 2025 •

3 min read

Vitamin K is an essential fat-soluble vitamin, crucial for blood clotting and bone health. To ensure adequate intake, it is important to understand: what are the main sources of vitamin K? This guide breaks down the two primary types of vitamin K and where to find them in your diet.

Quick Summary

This article details the primary dietary origins of vitamin K, specifically distinguishing between vitamin K1 (phylloquinone) from plants and vitamin K2 (menaquinones) from animal and fermented foods. It offers a comprehensive overview of the best food sources for each type, important for blood clotting and bone health.

Key Points

Two Primary Forms: Vitamin K exists as two main types, K1 (phylloquinone) from plants and K2 (menaquinones) from animal and fermented foods.
K1 from Leafy Greens: The most concentrated sources of vitamin K1 are dark leafy green vegetables like kale, spinach, and Swiss chard.
K2 from Fermented Foods: Natto, a fermented soybean dish, is an exceptionally high source of vitamin K2.
K2 from Animal Products: Sources of vitamin K2 include organ meats, egg yolks, and certain cheeses.
Enhanced Absorption: Combining vitamin K-rich vegetables with a dietary fat source, such as oil, improves the body's absorption of vitamin K1.
Important for Blood and Bones: Both forms of vitamin K are vital for blood clotting and are key for producing proteins that support bone mineralization and density.

The Two Forms of Vitamin K: K1 and K2

Vitamin K is not a single compound but a family of structurally similar, fat-soluble vitamins. The two primary forms found in the human diet are vitamin K1 (phylloquinone) and vitamin K2 (menaquinones). While both are important, they have different dietary sources and unique physiological functions in the body. Vitamin K1, the most common dietary form, is mainly derived from plants. Vitamin K2 is less prevalent and is found in certain animal and fermented foods. A well-rounded diet should incorporate sources of both to support a range of bodily functions, from coagulation to extra-hepatic processes like bone metabolism and cardiovascular health.

Main Sources of Vitamin K1 (Phylloquinone)

Vitamin K1 is predominantly found in plant-based foods, especially dark leafy green vegetables. This form of vitamin K is involved in photosynthesis, which explains its high concentration in chlorophyll-rich foods. However, absorption of K1 from plants is lower than from supplements, and eating them with a source of dietary fat can enhance bioavailability.

Key sources of vitamin K1 include:

Green leafy vegetables: This group is the most concentrated source. Examples include kale, spinach, collard greens, Swiss chard, mustard greens, turnip greens, and parsley.
Cruciferous vegetables: Vegetables like broccoli, Brussels sprouts, and cabbage contain significant amounts of K1.
Vegetable oils: Soybean and canola oils are notable sources, often found in salad dressings.
Some fruits: Certain fruits, though less potent than leafy greens, also contain vitamin K1, including blueberries, figs, grapes, and kiwi.

Main Sources of Vitamin K2 (Menaquinones)

Vitamin K2 is primarily found in animal-based foods and fermented foods, and it has a longer half-life in the body compared to K1. K2 plays a crucial role in extra-hepatic tissues like bone and arterial walls. Some K2 is also produced by bacteria in the gut, but dietary intake is essential.

Key sources of vitamin K2 (menaquinones) include:

Fermented foods: Natto, a traditional Japanese fermented soybean dish, is an exceptionally rich source of K2, particularly the MK-7 subtype. Other fermented foods like hard and soft cheeses, sauerkraut, and kimchi also contain K2, with concentrations varying based on fermentation.
Animal products: Modest amounts of K2 are found in animal products. Good sources include organ meats like liver, fatty meats, egg yolks, and cheese.
Dairy products: Full-fat dairy, such as butter and certain cheeses, are good sources of K2.

Comparison of Vitamin K1 and K2 Sources


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinones)
Primary Source	Plant-based foods	Animal-based and fermented foods
Best Food Examples	Kale, spinach, broccoli, soybean oil	Natto, hard cheeses, egg yolks, liver
Commonality in Diet	Most common dietary form in Western diets	Less common but highly bioavailable, especially MK-7 from natto
Main Role	Essential for hepatic functions, particularly blood clotting	Supports extra-hepatic functions, including bone mineralization and preventing vascular calcification
Bioavailability	Lower absorption from food matrix; enhanced by fat	Higher bioavailability, especially long-chain menaquinones like MK-7
Metabolism	Preferentially stored in the liver	Circulates longer and distributed more widely to extra-hepatic tissues

Ensuring Sufficient Vitamin K Intake

For most individuals, obtaining sufficient vitamin K from a balanced diet is achievable. The recommended Adequate Intake (AI) is 120 mcg daily for adult men and 90 mcg for adult women. Given the differences in bioavailability and function, consuming a variety of sources for both K1 and K2 is recommended. For those on anticoagulant medication like warfarin, maintaining a consistent daily intake is critical to avoid dangerous interactions.

It is important to incorporate both types of vitamin K into your meals. For example, a salad with spinach and a drizzle of canola oil provides vitamin K1, while adding some hard cheese or a side of meat contributes vitamin K2. Fermented foods like natto or sauerkraut can also be powerful additions to increase K2 levels. For further reading on dietary guidelines, the NIH Office of Dietary Supplements offers extensive information.

Conclusion

In summary, the main sources of vitamin K vary significantly between its two forms. Vitamin K1 is abundant in leafy green vegetables and some vegetable oils, making it the more common dietary source. Vitamin K2 is found in fermented foods and animal products, and its better absorption and wider distribution make it crucial for bone and cardiovascular health. For a comprehensive approach to nutritional health, a diverse diet rich in both plant-based K1 and K2-containing foods is the ideal strategy. While deficiencies are rare, focusing on these food groups can support essential bodily processes from proper blood clotting to maintaining strong bones.

Frequently Asked Questions

Vitamin K1 comes primarily from plant-based foods, such as leafy greens and certain vegetable oils. In contrast, vitamin K2 is found in animal products like liver, eggs, and cheese, as well as fermented foods like natto.

Yes, vitamin K content varies significantly across different foods. For instance, cooked kale and natto are exceptionally high in vitamin K, while eggs and many fruits contain much smaller amounts.

Cooking leafy greens concentrates their vitamin K content, but raw versions are still excellent sources. However, as vitamin K is fat-soluble, cooking with fat can enhance its absorption.

While bacteria in the gut produce some vitamin K2, the amount is generally not sufficient to meet the body's needs. Dietary intake of vitamin K from both K1 and K2 sources is necessary for optimal health.

No, while natto is the richest source of K2, other fermented foods like sauerkraut and certain cheeses (for ovo-lacto vegetarians) contain it. Vegetarians may need to be more mindful of their K2 intake.

If you are on anticoagulant medication, maintaining a consistent daily intake of vitamin K is crucial. Sudden changes can interfere with your medication's effectiveness. You should always consult your healthcare provider for specific dietary guidance.

Both forms of vitamin K play important but different roles in the body. While K1 is important for blood clotting, K2 plays a key role in bone and cardiovascular health. A balanced diet containing a variety of sources for both is the best approach.

You can add spinach or kale to smoothies and salads, use canola or soybean oil in your cooking, and include fermented foods like hard cheese or natto as part of your meals.