Kvitamiinin

The Kvitamiinin, commonly referred to as vitamin K, is a group of fat-soluble vitamins that play a critical role in blood coagulation and bone metabolism. In Finnish-language sources, the term K-vitamiini is used, with Kvitamiinin serving as the genitive form.

Vitamin K exists in several forms. Phylloquinone (K1) is mainly found in leafy greens and plant oils. Menaquinones (K2) are produced by gut bacteria and occur in animal products and fermented foods. A synthetic form, menadione (K3), is used in some feeds and supplements but is not generally recommended for routine human use.

The biological role of vitamin K is to act as a coenzyme for gamma-carboxylation of glutamate residues on vitamin K–dependent proteins. This modification is required for the proper activity of several clotting factors II, VII, IX, and X and the anticoagulant proteins C and S. It also influences bone metabolism through osteocalcin activation.

Vitamin K is absorbed with dietary fats and stored mainly in the liver. It is present in green leafy vegetables and plant oils (K1), while K2 forms are produced by intestinal bacteria and found in some animal products and fermented foods. The vitamin is recycled in the body by the enzyme VKOR.

Deficiency is uncommon in healthy adults but can occur with fat malabsorption, certain liver diseases, or prolonged antibiotic therapy. Newborns are at risk for hemorrhagic disease and routinely receive vitamin K prophylaxis. Vitamin K toxicity from diet is rare; high-dose supplements can interfere with anticoagulants such as warfarin.