What is the richest source of vitamin K?

November 4, 2025 •

3 min read

Although kale is widely praised for its vitamin K content, one fermented food, natto, provides a far greater concentration per serving. The richest source of vitamin K is more complex than just a single food, as it depends on whether you are seeking Vitamin K1 or K2 and the form of preparation.

Quick Summary

The richest source of vitamin K depends on the type sought, K1 or K2. Fermented soybeans (natto) are the highest source of K2, while cooked leafy greens provide the highest amounts of K1. This guide covers the top sources for each type and offers tips for better absorption.

Key Points

Natto is the most potent single source of vitamin K: This fermented Japanese soybean dish is incredibly rich in vitamin K2, far surpassing the concentration found in most other foods.
Cooked greens offer high levels of vitamin K1: Leafy greens like cooked spinach, kale, and collards are top sources of vitamin K1, often providing several times the daily recommended value in a single serving.
Absorption is improved with fat: Because it is a fat-soluble vitamin, consuming vitamin K-rich foods with some dietary fat, such as oil, improves the body's absorption.
Vitamin K is vital for bone and heart health: Beyond its role in blood clotting, adequate vitamin K intake supports bone mineral density and may help prevent arterial calcification.
Medication precautions: Individuals taking blood thinners like warfarin must maintain consistent vitamin K intake to avoid interfering with their medication's effectiveness.
Diverse sources for a balanced diet: To obtain both K1 and K2, include a mix of leafy greens, fermented foods like natto, and certain animal products and cheeses in your diet.

Natto: The Richest Source of Vitamin K2

While many people immediately think of leafy greens when asked about the richest source of vitamin K, the fermented soybean dish known as natto is, in fact, a super-concentrated source of vitamin K2. A small, 3-ounce serving of natto can contain an astonishing 850 mcg of vitamin K, far exceeding the daily recommended intake for adults. Vitamin K2 is particularly beneficial for bone health and is also found in animal products and some cheeses.

Other Top Sources of Vitamin K1 and K2

For those who may not be fond of natto's strong flavor and sticky texture, there are plenty of other potent sources of this essential nutrient. Vitamin K comes in two main forms: K1 (phylloquinone), predominantly found in plant foods, and K2 (menaquinone), found in animal products and fermented foods. Dark, leafy green vegetables are exceptionally rich in vitamin K1. Cooking these greens often concentrates the vitamin K content, making them even more potent than when raw.

Rich Sources of Vitamin K1

Kale: A single cup of cooked kale can provide well over 400% of the daily value for vitamin K.
Spinach: Cooked spinach is another powerhouse, with one cup offering around 888 mcg.
Collard Greens: These greens are a champion of vitamin K1, with half a cup of boiled, frozen collards providing 442% of the daily value.
Mustard Greens: Cooked mustard greens are also among the highest sources of vitamin K1.

The Role of Fats in Vitamin K Absorption

Vitamin K is a fat-soluble vitamin, which means it is best absorbed by the body when consumed with a source of dietary fat. For instance, sautéing leafy greens in a healthy oil like soybean or olive oil can significantly boost the bioavailability of vitamin K1. Similarly, the fats found naturally in cheese and eggs help the body absorb the vitamin K2 they contain.

Comparison of Top Vitamin K Sources (Per Serving)


Food Source	Type of Vitamin K	Serving Size	Approximate Vitamin K (mcg)	Notes
Natto	K2	3 oz	850	Fermented soybeans; very high concentration
Collard Greens (cooked)	K1	½ cup	530	High concentration of K1
Turnip Greens (cooked)	K1	½ cup	426	Excellent source of K1
Spinach (cooked)	K1	1 cup	888	Very high concentration of K1
Swiss Chard (cooked)	K1	1 cup	572	Provides over 400% of daily value
Goose Liver	K2	100g	369	A rich animal-based source of K2
Kale (cooked)	K1	1 cup	544	A well-known K1 source

The Benefits of a Vitamin K-Rich Diet

Beyond its reputation for blood clotting, vitamin K is also crucial for maintaining strong bones and supporting heart health. Adequate intake helps with calcium absorption and bone metabolism, which can reduce the risk of osteoporosis and fractures over time. Some studies also suggest potential benefits for heart health by preventing arterial calcification, particularly linked to vitamin K2.

Who Needs to Pay Attention to Vitamin K Intake?

Most healthy adults who consume a balanced diet easily meet their vitamin K needs. However, certain groups should monitor their intake more closely. This includes individuals on blood-thinning medications like warfarin, for whom consistent vitamin K consumption is essential to maintain the drug's effectiveness. Rapid fluctuations in vitamin K intake can interfere with these medications, so consulting a healthcare provider is vital.

Practical Ways to Incorporate More Vitamin K

For those aiming to increase their vitamin K intake, several simple strategies can be employed. Add a handful of spinach or kale to smoothies or stir-fries. Use kale as a base for salads or make your own crunchy kale chips. Incorporate chopped parsley or other fresh herbs into your dishes. For a quick and easy option, consider making a simple salad dressing using soybean or canola oil, which contain vitamin K.

Conclusion

While leafy greens like spinach and kale are exceptional sources of vitamin K1, the most potent single source is natto, providing an incredibly high concentration of vitamin K2. By incorporating a variety of these different foods into your diet, including both plant-based and fermented sources, you can easily meet and exceed your daily vitamin K needs for optimal blood, bone, and heart health. Whether you choose to boost your intake with a superfood like natto or stick with readily available greens, ensuring sufficient vitamin K is a simple and effective step toward a healthier lifestyle.

For more detailed information on dietary reference intakes for vitamins and other nutrients, the National Institutes of Health (NIH) Office of Dietary Supplements provides comprehensive fact sheets.

NIH Office of Dietary Supplements - Vitamin K Fact Sheet

Frequently Asked Questions

Vitamin K's primary and most well-known function is its role in blood clotting, where it is a cofactor for enzymes that produce proteins essential for coagulation.

Both vitamin K1 and K2 are important and have different metabolic roles. K1 is primarily for blood clotting, while K2 is more beneficial for bone and heart health by helping regulate calcium.

Yes, it is possible for most people to meet their daily vitamin K needs with a sufficient intake of leafy green vegetables, especially when cooked.

According to the NHS, it is unlikely to consume harmful levels of vitamin K from food alone, and excess vitamin K is not typically stored.

Since vitamin K is fat-soluble, you can increase its absorption by eating it alongside a source of fat, like cooking leafy greens in olive oil or having an avocado with your salad.

Some hard and fermented cheeses, such as Gouda and Danish blue cheese, contain notable amounts of vitamin K2.

No, not all fermented foods are high in vitamin K2. Natto is a particularly concentrated source, while others, like sauerkraut or pickled cucumber, may contain lesser but still significant amounts.