Does Your Body Convert K1 to K2? Unpacking Vitamin K Metabolism

November 20, 2025 •

4 min read

While vitamin K is best known for its role in blood clotting, this essential nutrient is actually a family of fat-soluble compounds with distinct functions. The question of whether your body converts K1 to K2 is crucial for understanding how to get enough of both forms to support bone and heart health.

Quick Summary

The body does convert vitamin K1 into vitamin K2, specifically the MK-4 subtype, through a complex metabolic pathway, but the process is inefficient. Dietary K2, particularly the MK-7 subtype from fermented foods and animal products, provides longer-lasting benefits for bone and cardiovascular health.

Key Points

Conversion is Inefficient: While the body can convert K1 to K2, the process is not very efficient, especially for the crucial MK-7 subtype.
Dietary K2 is Crucial: Relying on conversion alone is insufficient; prioritize consuming K2-rich foods like natto, hard cheeses, and grass-fed dairy.
Different Functions: K1 is primarily for blood clotting, while K2 is critical for bone and cardiovascular health.
Improve K1 Absorption: Eat K1-rich vegetables with healthy fats to boost absorption, as K1 is fat-soluble.
Consider Supplements: K2 supplements, especially the MK-7 form, can be beneficial for those with low dietary intake.
Gut Bacteria Contribution: Gut bacteria produce some K2, but the amount and bioavailability are uncertain.
MK-4 vs. MK-7: K1 is converted to MK-4 in certain tissues, but MK-7 from bacterial sources may have a longer-lasting effect.

Understanding the Two Primary Forms of Vitamin K

Vitamin K is not a single compound but rather a group of fat-soluble vitamins. The two most important forms are phylloquinone (vitamin K1) and menaquinones (vitamin K2). Understanding their differences is key to appreciating the complexities of how your body processes them.

Vitamin K1 (Phylloquinone)

Source: Predominantly found in green leafy vegetables like spinach, kale, and broccoli.
Function: Plays a critical role in blood coagulation by activating proteins necessary for proper blood clotting. The liver absorbs and uses most of the K1 consumed for this purpose.

Vitamin K2 (Menaquinone)

Source: Primarily found in animal products (e.g., meat, eggs, high-fat dairy) and fermented foods (e.g., natto, certain cheeses). It is also synthesized by bacteria in the gut.
Function: Known for its role in calcium metabolism, which is essential for bone health and preventing arterial calcification. K2 has different subtypes (menaquinones), with MK-4 and MK-7 being the most well-studied.

The Inefficient Conversion Process: Does your body convert K1 to K2?

Yes, your body does have the ability to convert K1 into K2, specifically the MK-4 subtype. However, the process is far from efficient, and relying on it alone may not provide adequate amounts of K2 for optimal health.

The Mechanisms of Conversion

There are two main sites where this conversion occurs:

Intestinal Conversion: Gut bacteria can convert some K1 into K2. However, the bioavailability of this bacterially-produced K2 is questionable, and it's unclear how much the body can effectively absorb and utilize.
Tissue-Specific Conversion: Animal studies have shown that K1 can be converted to the MK-4 form of K2 in specific tissues, including the pancreas, testes, and arterial walls. This process involves a complex pathway where the side chain of K1 is removed, and a new one is attached to form MK-4.

The Importance of Dietary Sources

Because the internal conversion is limited, obtaining both K1 and K2 from your diet is the most reliable strategy. Many people consume plenty of K1 from vegetables, but K2 is less common in the modern Western diet. Foods like natto, certain cheeses, and grass-fed dairy products are excellent sources of K2.

K1 vs. K2: A Comparison of Functions and Sources

To highlight the importance of each form, here is a comparison table outlining their key differences.


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Dietary Source	Green leafy vegetables	Fermented foods, animal products
Main Function	Blood coagulation	Calcium metabolism (bone and heart health)
Absorption Rate	Low bioavailability from plants (less than 10% absorbed)	Higher bioavailability, especially when consumed with fat
Transport in Body	Mainly transported to and utilized by the liver	Circulates longer in the blood to reach extra-hepatic tissues
Bioavailability	Relatively poor due to tight binding in plant chloroplasts	Generally higher, especially long-chain forms like MK-7

Optimizing Your Vitamin K Intake

Given the inefficiency of the K1 to K2 conversion, relying solely on leafy greens is not the best approach for maximizing K2 levels. Here are some strategies for optimizing your intake:

Prioritize K2-rich foods: Incorporate more fermented foods like natto and hard cheeses into your diet.
Pair K1 with fat: Since vitamin K is fat-soluble, consuming K1-rich vegetables with healthy fats (e.g., olive oil dressing) can significantly improve absorption.
Consider supplementation: For those who have difficulty getting enough K2 from their diet, supplements containing MK-7 are widely available and can be effective.

Conclusion: Focus on Dietary Diversity for Optimal Health

In summary, while your body does convert K1 to K2, the process is not efficient enough to rely on for optimal health. A balanced approach that includes both K1-rich leafy greens and K2-rich fermented and animal products is the most effective way to ensure adequate levels of both vitamins. By understanding the distinct roles and sources of K1 and K2, you can make informed dietary choices to support your long-term bone, heart, and overall health. For further reading, a scientific review on the emerging group of vitamin K benefits can provide deeper insights into the distinct actions of K1 and K2: Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health.

Resources and Further Reading

National Institutes of Health (NIH) Office of Dietary Supplements: Provides comprehensive facts sheets on vitamin K for both health professionals and consumers.
Healthline: Offers detailed articles explaining the differences between K1 and K2, their benefits, and food sources.
Wikipedia: Contains a thorough overview of the different forms of vitamin K, their biochemistry, and biological functions.
PubMed Central: Houses a wide range of peer-reviewed scientific studies on vitamin K, including research on the conversion and health outcomes.

Scientific Research

Study on K1 to MK-4 Conversion: A 2008 study published in the Journal of Nutrition Science and Vitaminology used deuterium-labeled K1 to confirm the conversion to MK-4 in mice tissues.
Review on Vitamin K's Role in Health: A 2017 review article in Nutrients discusses the distinct roles of K1 and K2 in health beyond coagulation.
Study on Vitamin K2 and Heart Health: A 2017 study in the Journal of American Heart Association examined the effect of MK-7 supplementation on arterial stiffness.

Frequently Asked Questions

Neither K1 nor K2 is inherently "better"; they have distinct, non-overlapping functions. K1 is crucial for blood clotting, while K2 is important for directing calcium to bones and away from arteries. Both are essential for optimal health.

No, you cannot reliably get all the K2 you need from converting K1. The conversion process is known to be inefficient, meaning you should not depend on it for your K2 requirements.

The K2 form, specifically the MK-7 subtype, is widely considered superior for bone health. It activates proteins that bind calcium to the bone matrix, promoting stronger bones and potentially reducing fracture risk.

The best food sources of vitamin K2 include fermented foods like natto and sauerkraut, as well as animal products like egg yolks, hard cheeses (gouda, edam), and grass-fed butter.

Severe vitamin K deficiency leading to bleeding issues is rare in adults but can occur in newborns who don't receive a prophylactic injection. Suboptimal levels of K2, however, are more common and can affect bone and heart health.

K2 supplements most often use the MK-7 form because it has a longer half-life and remains in the bloodstream longer than MK-4, allowing for more consistent activation of key proteins.

Yes, prolonged use of broad-spectrum antibiotics can destroy the good bacteria in the gut that produce K2, potentially lowering your vitamin K status. This can be a concern for those with poor dietary intake.

Yes, combining vitamin K with vitamin D is beneficial, as they work synergistically. Vitamin D helps with calcium absorption, while vitamin K helps direct that calcium to the bones and away from arteries.