What is a good source of K2 for bone and heart health?

November 16, 2025 •

3 min read

A 2012 study showed that MK-7, a form of K2, was well-absorbed from nutritional doses, unlike MK-4. But what is a good source of K2 in your diet? The answer lies in both fermented foods and animal products, with significant differences in the type and bioavailability of the menaquinone you consume.

Quick Summary

This article explores the best dietary sources of vitamin K2, differentiating between the MK-4 and MK-7 subtypes found in animal and fermented foods, respectively, and discusses the role of supplements.

Key Points

Natto is the richest source: This Japanese fermented soybean dish contains an exceptionally high concentration of the highly bioavailable MK-7 form of vitamin K2.
Fermented foods offer MK-7: In addition to natto, fermented foods like sauerkraut and specific aged cheeses (Gouda, Edam) are valuable sources of MK-7 produced by bacteria.
Animal products provide MK-4: The MK-4 subtype of K2 is found in high-fat animal products, including pasture-raised egg yolks, organ meats like liver, and certain fatty meats.
MK-7 has better bioavailability: Studies show that MK-7 has a longer half-life and accumulates more effectively in the bloodstream than MK-4, making it a more consistent source.
Supplements offer a consistent dose: For those who cannot consume or dislike K2-rich foods, particularly MK-7, a supplement is a reliable way to ensure adequate intake.
Source matters for content: The K2 content in animal products depends on the animal's diet (grass-fed vs. grain-fed), impacting the nutritional value.

Understanding Vitamin K2: The Two Main Forms

Vitamin K2, also known as menaquinone (MK), is a fat-soluble vitamin essential for regulating calcium metabolism, which directs calcium to your bones and teeth instead of soft tissues like arteries. This function is vital for both bone and heart health. Unlike Vitamin K1, primarily found in leafy greens, K2 is less common in Western diets, and its sources are often overlooked. It is crucial to understand the two most common forms, MK-4 and MK-7, to choose the right sources for your health goals.

MK-4: The Animal-Derived Vitamin

Menaquinone-4 (MK-4) is found in animal products and has a relatively short half-life in the bloodstream, meaning it is cleared from the body quickly, often within six to eight hours. For dietary MK-4 to be effective, it typically needs to be consumed in larger, more frequent doses. Key dietary sources include:

Pasture-raised eggs: The yolk contains a substantial amount of K2, particularly when the chickens are grass-fed.
Organ meats: Goose and chicken liver are particularly rich sources.
High-fat dairy: Products from grass-fed animals, such as ghee and butter, contain notable MK-4.
Certain meats: Chicken thighs and legs are better sources of K2 than lean cuts of meat.

MK-7: The Fermented Food Superstar

Menaquinone-7 (MK-7) is a long-chain menaquinone produced by bacteria during fermentation. It has a significantly longer half-life than MK-4, remaining in the body for up to 72 hours. This prolonged presence allows MK-7 to be more bioavailable and accumulate more effectively in the bloodstream with smaller, less frequent doses. The most powerful dietary source of MK-7 is natto, a traditional Japanese food. Other fermented foods offer varying amounts:

Natto: A traditional Japanese dish of fermented soybeans, natto is exceptionally high in MK-7, providing over 1,000 mcg per 100g.
Sauerkraut: This fermented cabbage is a good source of MK-7, offering both K2 and gut-healthy probiotics.
Certain cheeses: Hard and aged cheeses like Gouda and Edam, along with soft cheeses like Brie, contain measurable amounts of MK-7, produced by the specific bacteria involved in their ripening process.

Comparison of Key Vitamin K2 Sources

To help you decide on the best option for your diet, here is a comparison of some popular K2 sources based on their content and accessibility.


Source	MK Type	K2 Content (per 100g)	Accessibility	Notes
Natto	Primarily MK-7	Extremely high (~1000 mcg)	Limited; acquired taste for many Western palates	Highest known dietary source.
Hard Cheeses (e.g., Gouda, Edam)	MK-7, MK-8, MK-9	Varies (e.g., Gouda: ~32 mcg)	Widely available in many Western grocery stores	K2 levels vary significantly by cheese type and age.
Chicken Liver	MK-4	High (~11 mcg)	Accessible, but organ meats may be unpopular for some	Rich in other nutrients like Vitamin A and iron.
Supplements (MK-7)	MK-7	Depends on dosage (e.g., 45-180 mcg)	Widely available online and in stores	Provides a consistent and bioavailable source, especially for those who avoid K2-rich foods.

Should You Choose Food or Supplements?

For those who enjoy and can source fermented foods like natto or high-quality animal products, a food-first approach can be highly effective. For example, regularly consuming small amounts of natto can provide a powerful dose of MK-7. However, the exact amount of K2 in many foods can vary greatly, and consuming the necessary quantity can be challenging.

For many, supplementation is a more reliable way to ensure a consistent intake of K2, particularly the long-acting MK-7 form. This is especially beneficial for vegans, as MK-4 is not found in plant-based sources and supplements offer an accessible alternative. Supplements containing MK-7 are often recommended due to its superior bioavailability and longer half-life compared to MK-4.

Conclusion

Determining what is a good source of K2 depends on your dietary preferences and health goals. Natto and high-quality, grass-fed animal products offer a strong food-based approach, providing potent doses of MK-7 and MK-4, respectively. However, for those with dietary restrictions or who seek a consistent, guaranteed dosage, MK-7 supplements are a highly effective and convenient alternative. Consulting a healthcare provider or a registered dietitian can help you tailor your approach and determine the best strategy to ensure adequate vitamin K2 intake for optimal bone and cardiovascular health. For more detailed information on dosage and interactions, particularly if you are on blood-thinning medication like warfarin, it is crucial to speak with a medical professional.

Frequently Asked Questions

No, they are different forms of vitamin K. K1 is found in leafy greens and primarily functions in blood clotting, while K2, found in animal and fermented foods, plays a key role in calcium regulation for bone and heart health.

MK-7 is generally considered more bioavailable and effective for long-term health benefits, especially for bones, because it has a longer half-life and remains active in the bloodstream for a longer period compared to MK-4.

Yes, vegans can get the MK-7 form of K2 from fermented foods like natto and sauerkraut. However, as the MK-4 form is only from animal sources, supplements are often recommended to ensure sufficient intake.

Some hard and aged cheeses, like Gouda and Edam, contain good amounts of K2. The concentration varies significantly depending on the type of cheese, fat content, and ripening process.

Yes, supplements are a reliable way to get a consistent and measured dose of K2, especially the highly bioavailable MK-7 form. This is particularly useful for individuals who do not consume or have limited access to K2-rich foods.

While gut bacteria do produce small amounts of K2, the intestinal absorption is minimal and generally insufficient to meet the body's needs for bone and arterial health. Dietary intake is therefore necessary.

The K2 content in animal products like meat and dairy is dependent on the animal's diet. Grass-fed animals, for example, convert more K1 from grass into K2, leading to higher levels in their products compared to grain-fed animals.