Vitamin K is a fat-soluble vitamin (dissolves in fats). It is known as the coagulation vitamin (hence the “K” in its name) or the anti-hemorrhagic vitamin because of its vital role in blood clotting. A deficiency in this vitamin can result in various hemorrhagic disorders.
Forms of Vitamin K
Vitamin K occurs naturally in two forms:
- K1 (phylloquinone): derived from plants.
- K2 (menaquinone): produced by bacteria in the small intestine.
In addition to these two forms, there are synthetic analogs of vitamin K, most of which are derived from K3 (menadione), such as K4 and K5.
Why Is Vitamin K Important?
Vitamin K plays a critical role in the blood clotting process (coagulation), giving it its name as the coagulation vitamin. It is considered an anti-hemorrhagic factor, and its deficiency can lead to various hemorrhagic diseases. It is essential for synthesizing clotting factors II, VII, IX, and X. A deficiency in vitamin K disrupts the coagulation process, making it difficult to stop bleeding. Beyond its role in blood clotting, vitamin K is crucial for bone health because the formation of the protein osteocalcin, which regulates bone mineralization, also depends on vitamin K.
Recommended Daily Intake of Vitamin K
The required daily intake of vitamin K is not precisely defined but is estimated at 200–300 µg for adults.
Vitamin K Deficiency (Hypovitaminosis)
Vitamin K deficiency most commonly occurs in newborns because their intestinal bacterial flora has not yet developed. In healthy adults, hypovitaminosis is rare as vitamin K is continuously synthesized in the gastrointestinal tract. However, it can occur in individuals with increased fat absorption in the intestines, as vitamin K is fat-soluble and absorbed along with fats. Deficiency may also occur in individuals with bile insufficiency (due to liver disease or bile duct obstruction).
The consequence of vitamin K deficiency is a decreased concentration of a protein in the blood critical for the coagulation process, known as prothrombin. This condition is called hypoprothrombinemia. As coagulation is disrupted, symptoms may include:
- Bleeding from minimal trauma
- Bruising and hematomas
- Bleeding from any organ or tissue
- Prolonged menstrual cycles
Excess Vitamin K (Hypervitaminosis)
High doses of natural forms of vitamin K do not cause adverse effects and have no recorded toxicity. However, synthetic forms (such as menadione) can lead to the formation of Heinz bodies (red blood cell inclusions) and cause hemolytic anemia.
Foods Rich in Vitamin K
Certain foods are rich in vitamin K, including:
- Green leafy vegetables (spinach, lettuce, broccoli, Swiss chard, kale, cabbage, cauliflower, Brussels sprouts, etc.)
- Liver
- Peas
- Soy
- Fish oil
- Green tea
Recommendations for Patients on Oral Anticoagulant Therapy
Oral anticoagulant medications such as Warfarin, Sintrom, Pelentan, and Syncoumar are taken to prevent blood clotting. These medications must be taken exactly as prescribed, and their effects should be regularly monitored through blood tests (INR – International Normalized Ratio or PT – Prothrombin Time).
The intake of foods rich in vitamin K can influence INR or prothrombin time (PT). It is essential to maintain a consistent level of vitamin K in the diet. Foods rich in vitamin K should not be entirely avoided or eliminated but consumed in moderation and in approximately the same amounts. This approach helps prevent sudden changes in vitamin K levels, ensuring that INR remains within the recommended range.
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