Vitamin K

What is vitamin K?

Vitamin K is an essential fat-soluble vitamin. It was named after the German word Koagulation because its first recognized function involved blood clotting.

Vitamin K acts as a cofactor for enzymes that activate specific proteins involved in coagulation, bone metabolism and vascular biology.

Vitamin K1 and vitamin K2

Vitamin K1, or phylloquinone, is found mainly in green leafy vegetables. Vitamin K2 refers to a group of menaquinones produced by bacteria and found in fermented foods and selected animal products.

Important K2 forms include MK-4 and MK-7. They differ in side-chain length, metabolism and half-life.

Food sources

• Kale, spinach and other leafy greens
• Broccoli and Brussels sprouts
• Herbs such as parsley
• Natto and other fermented foods
• Egg yolk and selected cheeses

What functions does vitamin K have?

Vitamin K is required for the activation of clotting factors and proteins such as osteocalcin and matrix Gla protein.

Osteocalcin is involved in bone metabolism, while matrix Gla protein helps regulate calcium deposition in blood vessels and other soft tissues.

Vitamin K and bone health

Vitamin K contributes to the maintenance of normal bones. Observational studies have linked low vitamin K status with unfavorable bone outcomes, but supplementation studies have produced mixed results.

Vitamin K and vascular health

Because matrix Gla protein is involved in controlling vascular calcification, vitamin K2 is frequently discussed in cardiovascular research.

It is not yet established that vitamin K2 supplements prevent heart attacks or reverse vascular calcification in the general population.

Vitamin D and vitamin K

Vitamin D increases the production of several vitamin K-dependent proteins. This has led to the common combination of vitamins D3 and K2 in supplements.

The combination is biologically plausible, but the ideal dose and clinical benefit depend on individual circumstances.

Medication interactions

Vitamin K can strongly interfere with vitamin K antagonist anticoagulants such as warfarin or phenprocoumon. People taking these medicines should not change vitamin K intake or begin supplements without medical supervision.

Conclusion

Vitamin K is essential for blood clotting and contributes to normal bone maintenance. Vitamin K2 is scientifically interesting in relation to bone and vascular health, but supplementation should be individualized, especially when anticoagulant medication is used.