Vitamin K

Vitamin K is a group of fat-soluble vitamins essential for blood clotting, bone metabolism, and cardiovascular health. It exists in two primary forms: K1 (phylloquinone), found in leafy greens, and K2 (menaquinone), present in fermented foods and animal products. Beyond its well-known role in coagulation, emerging research highlights its potential benefits for bone density, insulin sensitivity, and reducing arterial calcification. Studies suggest vitamin K activates proteins that regulate calcium deposition, supporting both skeletal strength and vascular elasticity. While deficiency is rare in adults, inadequate intake may increase risks of fractures, heart disease, and excessive bleeding.

Key Facts

  • Vitamin K activates proteins critical for blood clotting and bone mineralisation.
  • Low vitamin K intake is linked to higher risks of osteoporosis and arterial calcification.
  • Fermented foods like natto (soybeans) are among the richest dietary sources of vitamin K2.
  • Newborns are routinely given vitamin K injections to prevent life-threatening bleeding.
  • Supplements may benefit individuals with fat malabsorption disorders or prolonged antibiotic use.
  • High-dose vitamin K1 (5 mg/day) has been shown to reduce fracture risk by over 50% in clinical trials.

What does the research say about vitamin K and its function in the body?

Research confirms vitamin K’s role in activating clotting factors and proteins like osteocalcin, which strengthens bones. Studies also suggest it helps prevent calcium buildup in arteries, reducing cardiovascular risks. Emerging evidence points to anti-inflammatory and insulin-sensitising effects, though further human trials are needed.

What are the primary food sources of vitamin K?

Leafy greens (kale, spinach) provide vitamin K1, while fermented foods (natto, cheese) and animal products (egg yolks, liver) offer K2. Broccoli, Brussels sprouts, and vegetable oils like soybean and canola are additional K1 sources. A single serving of natto covers over 1,000% of daily vitamin K needs.

How can I supplement vitamin K?

Supplements typically contain K1 or K2 (MK-4 or MK-7). K2-MK-7, derived from natto, has longer-lasting effects in the bloodstream. Always consult a healthcare provider before supplementing, especially if taking blood thinners like warfarin, as vitamin K can interfere with their efficacy.

What are the main symptoms of vitamin K deficiency?

Symptoms include easy bruising, nosebleeds, bleeding gums, and dark, tarry stools. In infants, deficiency may cause intracranial bleeding or jaundice. Those with liver disease or fat malabsorption disorders (e.g., cystic fibrosis) are at higher risk.

Are there any known side effects of supplementing vitamin K?

Vitamin K is generally safe, with no upper intake limit established. High doses may cause stomach upset, but serious side effects are rare. Individuals on anticoagulants should maintain consistent vitamin K intake to avoid medication fluctuations.

How long does it take to see the benefits of vitamin K supplementation?

Blood clotting improvements may occur within days, while bone density and cardiovascular benefits could take 6–12 months. Studies on arterial calcification show effects after 1–3 years of consistent supplementation.

What should consumers look for on the supplement label when supplementing vitamin K?

Opt for supplements specifying the form (K1 or K2-MK-7) and dosage (typically 50–200 mcg). Third-party testing certifications (e.g., USP, NSF) ensure quality. Avoid products with unnecessary additives or megadoses exceeding 1,000 mcg unless medically advised.

Can vitamin K interact with medications?

Yes, vitamin K can reduce the effectiveness of warfarin and other vitamin K antagonist anticoagulants. Patients on these medications should monitor their vitamin K intake closely and avoid sudden dietary changes.

Does vitamin K play a role in immune health?

Preliminary studies suggest vitamin K2 may modulate inflammation and support immune function, potentially reducing severity in respiratory infections like COVID-19. However, more research is needed to confirm these effects.

Is vitamin K beneficial for skin health?

Vitamin K creams are marketed for reducing bruising and dark circles, though evidence is limited. Internally, its role in preventing calcification might indirectly support skin elasticity by maintaining vascular health.


Sources