Vitamin K2 – The Forgotten Vitamin for Bones, Heart, and Calcium Routing

Vitamin K2 is the neglected counterpart to Vitamin D3 – and one of the most important nutrients that most people don't get enough of. As an activator of proteins that direct calcium to bones and keep it out of arteries, K2 is crucial for bone health and cardiovascular health.

Vitamin K1 vs. K2: Fundamental Differences

Property	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Main Source	Green leafy vegetables	Fermented foods, animal products
Primary Function	Blood clotting	Calcium regulation, bones, heart
Half-life	Short (~1–2h in plasma)	Long (K2 MK-7: ~72h)
Tissue Distribution	Primarily liver	Bones, arteries, extrahepatic tissue

Vitamin K2 Subtypes: MK-4 vs. MK-7

Form	Chain Length	Half-life	Source	Recommendation
MK-4	4 Isoprenes	~4–6h	Liver, butter, eggs	Needed 3–4x daily; higher doses (45 mg in Japan for osteoporosis)
MK-7	7 Isoprenes	~72h	Natto (fermented soybeans)	1x daily sufficient; preferred supplement form
MK-9	9 Isoprenes	Long	Cheese, fermented products	Present in natural sources

Key Proteins for K2 Action

Osteocalcin: Bone protein that anchors calcium in the bone matrix; activated by K2 (gamma-carboxylation). Without K2: Osteocalcin remains inactive (ucOC) and calcium cannot be incorporated
Matrix Gla Protein (MGP): Strongest known natural inhibitor of vascular calcification; activated by K2. Inactive MGP is a strong risk factor for atherosclerosis
Gas6 and Protein S: Regulate cell death and inflammation

The K2-D3-Calcium Triangle

Vitamin D3 significantly increases calcium absorption from the gut. Without sufficient K2, this calcium can deposit in arteries instead of bones. This explains why high vitamin D3 supplementation without K2 could increase cardiovascular risks.

Practical Recommendation: Always supplement Vitamin D3 + K2 (MK-7) together, especially with high D3 doses (>2,000 IU/day).

Evidence for Bones and Heart

Endpoint	Effect	Evidence
Bone Density	Significant improvement vs. placebo	Well-documented (several RCTs)
Fracture Risk	Reduced (MK-4 45 mg/day approved in Japan for osteoporosis)	Well-documented
Coronary Calcification	Slowed, partially reversible	Rotterdam Study: -50% CHD mortality with high K2 intake
Atherosclerosis Progression	Slowed by MGP activation	Well-documented

Dosage

General Prevention: 100–200 µg MK-7 daily
With high D3 dose (>4,000 IU): 200–400 µg MK-7
Osteoporosis (clinical): MK-4 45 mg/day (Japanese dosage, only under medical supervision)
Fat-soluble: Take with a fatty meal for optimal absorption

Frequently Asked Questions (FAQ)

Is Vitamin K2 safe with blood thinners (Warfarin)?

No – Vitamin K (all forms) interferes with the mechanism of action of Warfarin/Phenprocoumon. Patients on anticoagulants should ONLY take K2 supplements after consulting a doctor and with regular INR monitoring.

Why is K2 so often missing from the modern diet?

K2 is found mainly in fermented foods (natto, aged cheese) and organ meats/egg yolks from pasture-raised animals. These foods are rare in the modern Western diet. Natto (richest K2 source) is hardly eaten in Germany.