What Type of Vitamin K is Best for Bones?

December 18, 2025 •

3 min read

Research consistently suggests that for bone health, vitamin K2 is more beneficial than vitamin K1, with one meta-analysis on postmenopausal women showing that K2 supplementation had a positive effect on bone mineralization and strength. The crucial role of vitamin K2 lies in its ability to activate specific proteins that regulate how calcium is used throughout the body, ensuring it is deposited in the bones and not in the arteries.

Quick Summary

Studies show that vitamin K2 is the most effective form for increasing bone density and decreasing fracture risk, surpassing vitamin K1 in its ability to regulate calcium use and activate crucial bone-building proteins. The long-chain menaquinone-7 (MK-7) is particularly notable for its superior bioavailability and longer half-life compared to the shorter-chain MK-4, providing sustained support for skeletal strength.

Key Points

Vitamin K2 is Best for Bones: Specifically, vitamin K2 (menaquinone) is far more effective for bone health than vitamin K1 (phylloquinone).
Activates Bone-Building Proteins: Vitamin K2 activates proteins like osteocalcin and MGP, which direct calcium to bones for mineralization and keep it from calcifying arteries.
MK-7 is a Superior Form: The menaquinone-7 (MK-7) subtype of K2 has superior bioavailability and a longer half-life, ensuring a stable, consistent supply to the bones from a lower dose.
MK-4 is Less Convenient: While also effective at high doses, MK-4 has a short half-life and requires more frequent, much higher dosing to maintain therapeutic levels for bone health.
Synergy with Vitamin D3 and Calcium: Vitamin K2 works synergistically with vitamin D3 and calcium to ensure proper calcium absorption and allocation, maximizing benefits for skeletal and cardiovascular health.
Consider Supplements for Optimal Intake: While K2 is found in fermented foods and animal products, a high-quality MK-7 supplement is often the most practical way to ensure adequate and consistent intake.

Vitamin K's Role in Bone Metabolism

Vitamin K is a fat-soluble vitamin essential for numerous bodily functions, with two primary forms naturally occurring: vitamin K1 (phylloquinone) and vitamin K2 (menaquinones). While K1 is more renowned for its role in blood clotting, K2 is increasingly recognized as a key player in bone health. The primary mechanism involves activating two key proteins: osteocalcin and Matrix Gla Protein (MGP).

Osteocalcin Activation: Osteoblasts, the cells responsible for building new bone, produce osteocalcin. However, this protein is inactive until vitamin K carboxylates it, enabling it to bind calcium effectively. This process is vital for bone mineralization, which is the deposition of minerals like calcium to harden the bone matrix and increase strength.
MGP Regulation: MGP is a protein produced by vascular smooth muscle cells that inhibits the calcification of soft tissues, such as arteries. By activating MGP, vitamin K2 helps prevent calcium from building up in unwanted areas, directing it toward the skeletal structure.

Comparing Vitamin K1 vs. Vitamin K2 for Bones

While both forms of vitamin K are involved in the overall process, K2 demonstrates a more specific and effective influence on skeletal health due to differences in absorption, distribution, and half-life.


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinones)
Primary Function	Liver-based blood coagulation	Extra-hepatic tissue support (bones, arteries)
Dietary Sources	Green leafy vegetables (e.g., spinach, kale, broccoli)	Fermented foods (natto, some cheeses), animal products (egg yolks, liver, meat)
Bioavailability	Lower absorption rate; requires dietary fat	Higher absorption rate, especially from fatty foods
Half-Life	Short; clears from blood in a few hours	Long; circulates for several days (e.g., MK-7)
Effect on Bone	Weaker effect; primarily for short-term functions	Stronger, more sustained effect on bone mineralization

The K2 Subtypes: MK-4 vs. MK-7

Vitamin K2 consists of several subtypes, with the most studied being menaquinone-4 (MK-4) and menaquinone-7 (MK-7). These two forms have distinct properties that affect their impact on bone health.

MK-4: Found primarily in animal products, MK-4 has a short half-life and is cleared from the bloodstream rapidly. Studies using pharmacological doses of 45 mg per day (far exceeding typical dietary intake) have shown positive effects on bone density and fracture risk, particularly in Japanese studies. However, maintaining effective levels requires multiple doses throughout the day.
MK-7: A longer-chain menaquinone found in fermented foods like natto, MK-7 boasts a significantly longer half-life, allowing it to accumulate in the bloodstream and provide a more stable, prolonged supply. This means smaller, once-daily doses (around 100–180 mcg) are sufficient to support bone health and cardiovascular functions. Its superior bioavailability and sustained action make it a more convenient and potentially more effective option for long-term support.

Synergistic Role with Vitamin D3 and Calcium

Vitamin K2 does not work alone; its effectiveness is significantly enhanced when combined with other key nutrients for bone health, such as vitamin D3 and calcium.

Vitamin D3: This vitamin is crucial for promoting calcium absorption from the gut. However, without sufficient vitamin K2, this increased calcium can be deposited in soft tissues instead of being directed to the bones. Vitamin K2 effectively completes the process initiated by vitamin D3, ensuring calcium is delivered to the right place.
Calcium: The fundamental mineral for building bone, calcium intake should be adequate to support the bone-building process. Combining calcium, vitamin D3, and vitamin K2 creates a powerful trifecta for optimal skeletal health.

Conclusion

For optimal bone health, vitamin K2 is unequivocally superior to K1 due to its superior bioavailability and specific function in activating the proteins responsible for bone mineralization. Between the two main K2 subtypes, MK-7 offers a more practical and effective option for most people due to its longer half-life, allowing for consistent, once-daily dosing. The highest-quality evidence for supplementation is often derived from studies combining vitamin K2 with vitamin D3 and calcium, emphasizing the synergistic relationship between these essential nutrients. Individuals, particularly those at risk for osteoporosis like postmenopausal women, should focus on dietary sources rich in K2, especially fermented foods, or consider a high-quality MK-7 supplement after consulting a healthcare professional.

Additional resources

For further reading on the scientific evidence behind vitamin K2's role in bone and cardiovascular health, see this comprehensive article from the National Institutes of Health: Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health.

Frequently Asked Questions

Vitamin K2 is far more effective for bone health than vitamin K1. While K1 primarily aids in blood clotting in the liver, K2 specifically activates proteins like osteocalcin, which bind calcium to the bone matrix to increase density.

For most people, MK-7 is considered the better and more convenient form of vitamin K2. It has a longer half-life, meaning it stays in the body longer, requiring lower, once-daily doses to support bone health effectively.

Getting sufficient vitamin K2 from diet alone can be challenging, especially in Western diets. Excellent food sources include fermented foods like natto and some cheeses, as well as egg yolks and organ meats. Due to its concentration, a supplement is often the most reliable option for optimal intake.

Vitamin K2 works in harmony with vitamin D3 and calcium. Vitamin D3 increases the absorption of calcium, while vitamin K2 activates proteins that guide this calcium specifically to the bones, preventing its buildup in soft tissues and arteries.

Vitamin K2 supplementation is generally considered safe, with no reported adverse effects even at higher doses. However, it can interfere with blood-thinning medications like warfarin, so anyone on such medication should consult a doctor before starting K2.

One indicator of suboptimal vitamin K status is a high level of undercarboxylated osteocalcin (ucOC) in the blood. This suggests that there isn't enough vitamin K to properly activate bone-building proteins. A high ucOC-to-cOC ratio is also associated with an increased fracture risk.

Studies, particularly using higher doses of vitamin K2 (MK-4), have shown improvements in bone density and a reduction in fracture risk, especially in postmenopausal women with osteoporosis. While promising, some meta-analyses show mixed results, so it is best to discuss supplementation with a healthcare provider.