Is Vitamin K1 or K2 Better for You? A Nutrition Diet Guide

October 13, 2025 •

4 min read

While most of the vitamin K consumed in a typical Western diet is K1 from leafy greens, emerging evidence highlights the unique, potent benefits of K2. So, is vitamin K1 or K2 better for you? The answer depends heavily on your specific health objectives, as their roles within the body are distinct and complementary.

Quick Summary

Vitamin K1 primarily supports liver function for blood clotting, whereas K2 targets extra-hepatic tissues to bolster bone and cardiovascular health. Their differences in dietary sources and bioavailability affect how each impacts the body.

Key Points

Distinct Functions: Vitamin K1 primarily acts in the liver to facilitate blood clotting, while K2 performs more extra-hepatic functions for bone and heart health.
Superior Bioavailability: K2, particularly the MK-7 subtype found in natto, has significantly higher bioavailability and a longer half-life than K1 from plants.
Heart Health Champion: K2 is linked to a reduced risk of arterial calcification and heart disease by activating Matrix Gla Protein (MGP).
Bone Density Support: K2 is more effective at promoting bone mineralization by activating osteocalcin, whereas K1 has shown inconsistent effects on bone density.
Balanced Diet is Best: The optimal approach is to consume both leafy greens for K1 and fermented or high-fat animal products for K2 to get the full spectrum of benefits.
Medication Caution: Individuals on warfarin must be cautious with their intake of all forms of vitamin K, as sudden changes can affect medication efficacy.

The Vitamin K Family: K1 vs. K2

Vitamin K is a family of fat-soluble vitamins that play a crucial role in activating proteins necessary for essential bodily functions. While many people are only familiar with 'vitamin K' as a single entity, it primarily exists in two forms in the human diet: vitamin K1 (phylloquinone) and vitamin K2 (menaquinones). Though they share a core structure, their varying side chains cause them to function differently in the body and come from entirely different food sources.

What is Vitamin K1?

Known as phylloquinone, vitamin K1 is predominantly found in plant-based foods, especially dark leafy green vegetables. It makes up the bulk of vitamin K intake in many diets. Its primary function is to support the liver's production of blood-clotting proteins. Without adequate K1, the blood's ability to clot is compromised, leading to excessive bleeding.

What is Vitamin K2?

Vitamin K2, or menaquinone, is a group of compounds synthesized by bacteria. It is found in fermented foods and some animal products. K2 exists in several subtypes, labeled MK-4 through MK-13, based on the length of their side chain. This structural difference gives K2 its unique and more diverse extra-hepatic (outside the liver) functions. A significant amount of attention is given to MK-7, found in fermented foods like natto, due to its high bioavailability and long half-life.

Key Differences in Bioavailability and Function

One of the most notable distinctions between K1 and K2 is how the body absorbs and utilizes them. Vitamin K1 from plants is tightly bound within plant tissue, resulting in poor absorption unless consumed with fat. For instance, one study suggested less than 10% of K1 from plants is absorbed. In contrast, vitamin K2, especially the long-chain forms like MK-7, is more readily absorbed and has a longer half-life, staying in the blood for days compared to K1's hours.

This longer circulation time for K2 allows it to be more effectively utilized by extra-hepatic tissues like bones and blood vessels. While K1 is quickly cleared by the liver to regulate blood coagulation, K2 can travel throughout the body to activate proteins that serve other vital roles.

Which is "Better"? The Role in Specific Health Areas

The question of which is better depends on the health benefit in focus. Both are essential, but they excel in different physiological tasks.

Vitamin K and Blood Clotting

For blood coagulation, K1 has traditionally been the more recognized and studied form. It’s the standard treatment for excessive bleeding due to vitamin K deficiency. However, K2 also plays a role, with studies showing a single serving of K2-rich natto can have a prolonged and significant effect on blood clotting measures. Individuals on blood-thinning medication like warfarin must monitor intake of both types carefully, as they can interfere with treatment.

Vitamin K for Bone Health

In the realm of bone health, K2 shows a superior effect. K2 activates osteocalcin, a protein that binds calcium to the bone matrix, strengthening bones. Observational studies and some controlled trials suggest K2 supplementation can improve bone density and reduce fracture risk in postmenopausal women. While some studies show K1 has an inconsistent effect on bone density, others indicate it may reduce fracture incidence. For optimal bone health, K2 is often recommended alongside vitamin D and calcium.

Vitamin K and Cardiovascular Health

Perhaps the most compelling evidence for K2's specific benefits lies in its impact on heart health. K2 activates Matrix Gla Protein (MGP), which prevents calcium from depositing in arteries and soft tissues. Arterial calcification is a major risk factor for heart disease. The landmark Rotterdam Study in 2004 found that high intake of K2, but not K1, was associated with a reduced risk of severe aortic calcification and coronary heart disease mortality. While more research is needed, the mechanisms and observational data strongly favor K2 for cardiovascular wellness.

Comparison of Vitamin K1 vs. K2


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Sources	Leafy greens (kale, spinach), broccoli, Brussels sprouts, some vegetable oils.	Fermented foods (natto, aged cheese), organ meats, egg yolks, poultry.
Bioavailability	Poorly absorbed from plant sources; absorption improved with fat.	Higher bioavailability, especially for forms like MK-7.
Half-life	Short (hours), quickly cleared by the liver.	Long (days for some forms like MK-7), remains in circulation longer.
Primary Function	Activating hepatic (liver) proteins for blood clotting.	Activating extra-hepatic proteins for bone and vascular health.
Key Health Benefits	Essential for proper blood coagulation and preventing hemorrhaging.	Superior for bone mineral density, reducing arterial calcification, and supporting cardiovascular health.

Dietary Sources of Vitamin K1 and K2

To ensure a comprehensive intake of both forms, it's beneficial to consume a variety of foods.

Key Vitamin K1 Sources:

Leafy Greens: Spinach, kale, Swiss chard, collard greens.
Cruciferous Vegetables: Broccoli, Brussels sprouts.
Other Vegetables: Parsley, green beans.
Oils: Soybean and canola oil contain K1.

Key Vitamin K2 Sources:

Natto: Japanese fermented soybeans, exceptionally rich in MK-7.
Cheeses: Hard and aged cheeses like Gouda, Edam, and Munster.
Animal Products: Egg yolks, organ meats (like beef liver), and dark meat chicken.
Fermented Foods: Some varieties of sauerkraut.

Conclusion: Getting the Best of Both Worlds

Ultimately, the question of whether is vitamin K1 or K2 better for you has no simple answer. Both are vital and perform distinct, non-interchangeable functions in the body. While K1 is crucial for blood clotting, K2 excels at preventing arterial calcification and promoting bone strength. For optimal health, a balanced diet that includes sources of both is the ideal strategy. Include plenty of leafy greens for K1 and introduce fermented and grass-fed animal products for K2. Given their fat-soluble nature, consuming these foods with a healthy fat source can enhance absorption. Always consult a healthcare provider before starting any new supplement, particularly if you are on anticoagulant medications like warfarin. Achieving a balanced intake of both K1 and K2 is a proactive approach to supporting long-term health.

For more detailed dietary information, review the NIH Vitamin K Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/.

Frequently Asked Questions

Vitamin K1 is traditionally considered the primary form for blood clotting, as it is rapidly taken up by the liver to activate the necessary coagulation proteins. However, vitamin K2 also influences clotting, and individuals on anticoagulants must monitor their intake of both.

While the typical Western diet provides plenty of K1 from vegetables, K2 intake is often low. To increase K2, you need to regularly consume fermented foods like natto or aged cheese, as well as high-fat animal products like egg yolks and organ meats.

Yes, a limited amount of K1 can be converted into K2 (specifically MK-4) in certain tissues. However, this process is not very efficient, and relying solely on this conversion may not provide sufficient K2 for extra-hepatic functions like bone and heart health.

While K1 is vital for overall health, most controlled studies suggest that K1 supplementation alone has limited benefits for improving bone mineral density. K2 is generally considered more effective for this purpose.

For extra-hepatic benefits like cardiovascular and bone health, K2 is often considered a more effective supplement due to its higher bioavailability and longer circulation time. K1 supplements are typically used for coagulation-related issues.

Since vitamin K is fat-soluble, you can significantly improve absorption by consuming K-rich foods with a source of dietary fat, such as cooking leafy greens with olive oil or eating cheese with your vegetables.

Natural forms of vitamin K (K1 and K2) have a low potential for toxicity and no upper limit has been set. However, it is crucial to consult a doctor before supplementing, especially if you are taking blood-thinning medications like warfarin, as vitamin K can interfere with their action.