The Major Roles of Vitamin K in the Body

November 15, 2025 •

3 min read

Disclaimer: Information provided is for general knowledge and should not be considered medical advice. Consult with a healthcare provider before making health decisions. Vitamin K is a fat-soluble vitamin essential for many physiological processes.

Quick Summary

Vitamin K is a fat-soluble vitamin crucial for activating proteins involved in vital physiological processes. Its primary functions include promoting blood clotting, supporting bone mineralization, and contributing to cardiovascular health by preventing arterial calcification. A deficiency can lead to serious health complications.

Key Points

Blood Coagulation: Vitamin K is essential for activating clotting factors in the liver to ensure proper blood clotting and prevent excessive bleeding.
Bone Health: It plays a vital role in bone mineralization by activating osteocalcin, a protein that helps integrate calcium into bone tissue.
Cardiovascular Health: Vitamin K helps prevent vascular calcification, the hardening of arteries, by activating Matrix Gla Protein (MGP).
Different Forms: The two primary forms, K1 (phylloquinone) and K2 (menaquinone), have different dietary sources and functions, with K1 focusing on liver function and K2 on extrahepatic tissues.
Protein Activation: Vitamin K acts as a cofactor for enzymes that activate vitamin K-dependent proteins (VKDPs) in various tissues throughout the body.
Deficiency Prevention: Sufficient intake is crucial, as deficiency can lead to severe bleeding issues, weakened bones, and potentially increased cardiovascular risk.

What are the major roles of vitamin K in the body?

Vitamin K is a fat-soluble vitamin group, primarily Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinone). It acts as a cofactor for enzymes that activate vitamin K-dependent proteins (VKDPs). These activated proteins bind calcium and are essential for various bodily functions, particularly in blood, bone, and vascular tissues.

The crucial role in blood clotting

Vitamin K is essential for blood coagulation, preventing excessive bleeding. It activates clotting factors like II, VII, IX, and X in the liver through gamma-carboxylation. This allows them to bind calcium, which is vital for the coagulation cascade. Activated clotting factors form a fibrin mesh to stop bleeding, a process so crucial that newborns often receive vitamin K to prevent Vitamin K deficiency bleeding (VKDB).

Support for strong bones and bone metabolism

Vitamin K is also vital for bone health. It activates osteocalcin, a protein made by bone-building cells, which is necessary for binding calcium and integrating it into the bone matrix. This process increases bone mineral density and strength. Studies suggest vitamin K intake is linked to fewer hip fractures, especially in older adults.

Contribution to cardiovascular health

Research indicates Vitamin K, particularly K2, protects cardiovascular health by preventing arterial calcification. It activates Matrix Gla Protein (MGP) in blood vessel walls, which inhibits calcium deposits that harden arteries. This maintains blood vessel elasticity and helps prevent atherosclerosis and heart disease. Low vitamin K is linked to increased arterial calcification, while sufficient K2 intake can support cardiovascular health by ensuring MGP activation.

Comparison of Vitamin K1 and Vitamin K2 roles


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Dietary Source	Green leafy vegetables (spinach, kale, broccoli), vegetable oils	Animal products (meat, eggs, dairy) and fermented foods (nattō, cheese)
Main Role	Essential for activating liver-based blood clotting proteins	Functions mainly in extrahepatic tissues, supporting bone and cardiovascular health
Tissue Distribution	Concentrated in the liver, where it is rapidly used	Redistributed throughout the body, including bone and vascular tissues
Half-Life	Short half-life, meaning it is quickly processed and excreted	Longer half-life, allowing it to provide sustained benefits to other tissues
Research Focus	Well-established for its role in coagulation and deficiency prevention	Growing evidence highlights its crucial role in preventing arterial calcification and supporting bone strength

Other physiological functions

Additional research explores other potential roles of vitamin K, including:

Cell growth and signaling: The VKDP Growth arrest-specific protein 6 (Gas6) may influence cell proliferation and migration.
Neurological function: Some studies suggest K2 might have neuroprotective effects and support cognitive function.
Inflammation and immunity: Certain K2 forms may modulate inflammatory markers.

Conclusion

The major roles of vitamin K in the body are crucial for blood clotting, bone mineralization, and preventing vascular calcification, extending beyond its well-known coagulation function. Both Vitamin K1 and K2 are important and found in various foods like leafy greens, fermented products, and animal sources. Adequate intake is vital for long-term health and well-being. Ongoing research continues to reveal the broad importance of this essential nutrient. Learn more about vitamin K from the NIH Office of Dietary Supplements.

Frequently Asked Questions

The primary role of vitamin K is its involvement in blood coagulation, or clotting. It is required to activate specific proteins, known as clotting factors, that are produced in the liver. Without enough vitamin K, the blood's ability to clot is impaired, leading to a risk of excessive bleeding.

Vitamin K contributes to bone health by activating osteocalcin, a protein produced by bone-building cells. The activation of osteocalcin is essential for binding calcium and integrating it into the bone matrix, which increases bone mineral density and strength.

Vitamin K1 (phylloquinone) comes mainly from leafy green vegetables and is primarily used by the liver for blood clotting. Vitamin K2 (menaquinone) is found in animal products and fermented foods and is utilized by extrahepatic tissues for functions like preventing arterial calcification and supporting bone health.

Some studies suggest that vitamin K, particularly Vitamin K2, can help protect against heart disease. It does this by activating Matrix Gla Protein (MGP), which helps prevent the buildup of calcium in the arteries, a key risk factor for cardiovascular disease.

While rare in healthy adults, vitamin K deficiency can occur in newborns, individuals with malabsorption disorders like cystic fibrosis or celiac disease, and those on long-term antibiotic therapy. Newborns are especially vulnerable and are routinely given a prophylactic injection.

Good food sources of vitamin K1 include green leafy vegetables such as kale, spinach, broccoli, and Brussels sprouts. Sources of vitamin K2 include fermented foods like nattō and certain cheeses, as well as meat, eggs, and dairy products.

For natural forms of vitamin K (K1 and K2), toxicity is extremely rare, even with high intakes. However, those on blood-thinning medication like warfarin must maintain a consistent intake of vitamin K, as sudden changes can interfere with the drug's effectiveness and cause dangerous complications.