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Vitamin K1 (Phylloquinone)

fat-soluble

Vitamin
(15 studies)

Key Takeaways

  • Primary dietary form found in green leafy vegetables
  • FDA daily value is 120 mcg
  • Essential for coagulation factors II, VII, IX, X
  • Activates osteocalcin and matrix Gla protein
  • Less bioactive in extrahepatic tissues than K2

Evidence Spectrum

15 studies reviewed →
Strong (1)
Moderate (1)
Emerging (1)

Blood coagulation

Established cofactor for coagulation factors. Warfarin works by antagonizing vitamin K.17

Bone health

Combined K1+D3+calcium increased BMC at ultradistal radius in 2-year RCT. K1 alone did not prevent bone loss (pmid:17243866).248

Cardiovascular calcification prevention

K1 activates MGP (calcification inhibitor) but is less efficient than K2 for vascular tissue.356

15

Studies Reviewed

120 mcg

RDA (Adults (FDA Daily Value))

fat-soluble

Solubility

Role in the Body

Vitamin K1 (phylloquinone) is the primary dietary form, cofactor for gamma-glutamyl carboxylase activating 18+ vitamin K-dependent proteins (pmid:34472618). Primarily transported to liver for coagulation; less efficiently transported to extrahepatic tissues than K2 (pmid:21088475, pmid:8642455). Also activates osteocalcin and MGP for bone and vascular health (pmid:11706280, pmid:21155624).

  • Cofactor for gamma-glutamyl carboxylase
  • Coagulation factor activation (II, VII, IX, X, protein C, protein S)
  • Osteocalcin activation for bone
  • Matrix Gla protein activation against vascular calcification
  • Cell growth regulation via Gas6

Supplement Forms

Phylloquinone (K1)

Recommended

Bioavailability: 0.1%

Absorbed with dietary fat via chylomicrons (pmid:8642455)

Dihydrophylloquinone

Bioavailability: 0.05%

From hydrogenated oils; reduced activity (pmid:8827693)

Food Sources

Kale

Spinach

Collard greens

Broccoli

Brussels sprouts

Swiss chard

Parsley

Soybean oil

Deficiency

Prevalence: Uncommon in healthy adults; well-recognized in newborns and fat malabsorption (pmid:34472618).

Symptoms:

  • Easy bruising and bleeding
  • Prolonged prothrombin time
  • Hemorrhagic disease of newborn
  • Elevated undercarboxylated osteocalcin

Risk Factors:

  • Newborn infants
  • Fat malabsorption (CF, celiac)
  • Antibiotic therapy
  • Warfarin use

Safety & Interactions

Possible Side Effects:

  • • No known toxicity from natural K1

Drug Interactions:

  • • Warfarin: K1 directly opposes anticoagulant effects (pmid:21155624)
  • • Orlistat may reduce absorption

Contraindications:

  • • Warfarin patients must maintain consistent K intake

Frequently Asked Questions

K1 vs K2?

K1 (plants) goes mainly to liver for coagulation. K2 (fermented foods) reaches bone and arteries more effectively.

Can I take K1 on blood thinners?

Maintain consistent intake; do not supplement without medical guidance.

Research Sources

15 peer-reviewed studies analyzed from PubMed. 8 directly cited in this review.

View All Sources
1Vitamin K - sources, physiological role, kinetics, deficiency, detection, therapeutic use, and toxicity.
2Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women.
3Role of Vitamin K in Chronic Kidney Disease: A Focus on Bone and Cardiovascular Health.