Vitamin K₁ (Phylloquinone)

Basic Information

• Chemical Properties
   
  Phylloquinone has the molecular formula C31​H46​O2​. As a fat-soluble compound, its absorption in the small intestine requires the presence of bile salts and dietary fat. It is relatively stable to heat but can be degraded by prolonged exposure to light, especially ultraviolet radiation, and by alkaline conditions during cooking.
• Food Sources
   
  Vitamin K₁ is abundant in green leafy vegetables, with the highest concentrations found in kale, spinach, collard greens, Swiss chard, and broccoli. Other plant sources include Brussels sprouts, asparagus, and some vegetable oils (e.g., soybean oil, canola oil). Unlike vitamin B₁₂, it is not present in animal-derived foods in significant amounts.

Physiological Functions

1. Blood Coagulation

    

   This is the most well-documented function of vitamin K₁. It acts as a cofactor for the enzyme γ-glutamyl carboxylase, which is responsible for activating several key clotting factors in the liver (including factors II, VII, IX, X). Without sufficient vitamin K₁, these clotting factors remain inactive, increasing the risk of excessive bleeding and bruising.
    
2. Bone Health Maintenance

    

   Vitamin K₁ supports bone metabolism by activating osteocalcin—a protein that binds calcium to the bone matrix, promoting bone mineralization and strength. It also helps regulate the activity of matrix Gla protein (MGP), which prevents calcium accumulation in soft tissues (e.g., blood vessels), reducing the risk of vascular calcification.
    
3. Potential Cardiovascular Benefits

    

   By inhibiting vascular calcification via MGP activation, adequate vitamin K₁ intake may help lower the risk of cardiovascular diseases such as atherosclerosis. However, more clinical research is needed to confirm these effects.
    

Deficiency and Toxicity

• Deficiency Symptoms
   
  Vitamin K₁ deficiency is rare in healthy adults with a balanced diet, as gut bacteria can also synthesize small amounts of vitamin K. At-risk groups include newborns (who have sterile guts and low vitamin K stores), individuals with malabsorption disorders (e.g., celiac disease, Crohn’s disease), and those taking long-term anticoagulant medications (e.g., warfarin) that interfere with vitamin K metabolism. Symptoms of deficiency include easy bruising, prolonged bleeding from cuts, nosebleeds, and in severe cases, internal bleeding.
• Toxicity
   
  Vitamin K₁ has a very low toxicity profile. Unlike fat-soluble vitamins A and D, excess phylloquinone is not stored in the body in toxic amounts and is readily excreted via bile and urine. No serious adverse effects have been reported with oral supplementation at typical doses. High doses may, however, reduce the effectiveness of anticoagulant drugs like warfarin.

Recommended Intake