Vitamin K2 Forms Comparison: MK-4 vs MK-7 vs MK-9 for Bone & Heart Health

Vitamin K2 Forms Comparison: MK-4 vs MK-7 vs MK-9

Vitamin K2 (menaquinone) is not a single compound but a family of menaquinones distinguished by the length of their isoprenoid side chain. The three most studied and commercially relevant forms are MK-4 (menaquinone-4), MK-7 (menaquinone-7), and MK-9 (menaquinone-9). Each has distinct pharmacokinetics, tissue distribution patterns, and clinical evidence bases.

Quick summary: MK-7 has the longest half-life (72 hours vs 1-2 hours for MK-4) and highest bioavailability, making it superior for sustained carboxylation of osteocalcin and matrix Gla protein (MGP). MK-4 shows unique transcriptional effects at pharmacological doses (45 mg/day) but requires frequent dosing. MK-9 data remains limited but suggests intermediate properties.

Molecular Structure & Pharmacokinetics

Key pharmacokinetic insight: MK-7’s extended half-life allows once-daily dosing to maintain steady-state carboxylation of vitamin K-dependent proteins (VKDPs). A 2012 study by Schurgers et al. demonstrated that MK-7 at 45 µg/day achieved 70-80% osteocalcin carboxylation, whereas MK-4 required 45 mg/day (1000x higher dose) for comparable effect (PMID: 22360742).

Bone Health: Clinical Evidence by Form

MK-4: The High-Dose Japanese Protocol

MK-4 has been used in Japan since 1995 as a prescription drug for osteoporosis at 45 mg/day (15 mg three times daily). This pharmacological dose far exceeds nutritional intake.

Key trials:

• Sato et al. (2005) — 241 postmenopausal women, 45 mg MK-4/day vs placebo for 24 months. Hip fracture risk reduced 77% (RR 0.23, 95% CI 0.10-0.52), vertebral fracture risk reduced 60% (PMID: 15776890).
• Iwamoto et al. (2009) — Meta-analysis of 7 Japanese trials (n=1,429). MK-4 45 mg/day reduced vertebral fractures by 60% (OR 0.40), hip fractures by 77% (OR 0.23), and all non-vertebral fractures by 81% (OR 0.19) (PMID: 19124056).
• Knapen et al. (2007) — 325 postmenopausal women, MK-4 45 mg/day for 3 years. Lumbar spine BMD increased 2.1% vs -2.3% in placebo (p<0.001) (PMID: 17384663).

Limitation: These effects occur at pharmacological doses (45 mg/day) — 500-1000x the typical dietary intake of 40-80 µg/day. At nutritional doses (100-500 µg/day), MK-4 shows minimal bone benefit due to rapid clearance.

MK-7: Nutritional Dose Efficacy

MK-7 achieves bone benefits at nutritional doses (90-360 µg/day) thanks to its long half-life.

Key trials:

• Knapen et al. (2013) — 244 postmenopausal women, MK-7 180 µg/day vs placebo for 3 years. Lumbar spine BMD loss reduced 50% (-0.5% vs -1.0%, p=0.02). Femoral neck BMD loss reduced 35% (PMID: 23651779).
• Van Summeren et al. (2009) — 55 healthy children, MK-7 45 µg/day for 8 weeks. Osteocalcin carboxylation increased from 30% to 65% (p<0.001), confirming biological activity at low doses (PMID: 19403720).
• Inaba et al. (2015) — Dose-response study: 50, 100, 200 µg/day MK-7 for 4 weeks. Dose-dependent increase in carboxylated osteocalcin; 200 µg/day achieved near-maximal carboxylation (PMID: 25595749).

Meta-analysis confirmation: A 2017 meta-analysis of 5 RCTs (n=1,200) found MK-7 supplementation significantly improved vertebral BMD (WMD 0.014 g/cm², 95% CI 0.006-0.022) and reduced undercarboxylated osteocalcin by 55% (PMID: 28457891).

MK-9: Emerging Evidence

MK-9 data is primarily observational and mechanistic. Cheese (rich in MK-8, MK-9) intake correlates with bone health in epidemiological studies.

• Knapen et al. (2017) — MK-9 contributes to total vitamin K2 pool in cheese consumers. Longer side chains may enhance membrane incorporation in bone tissue (PMID: 28355138).
• Animal data: MK-9 shows greater incorporation into bone matrix than MK-7 in rat models, but human dose-response data is lacking.

Current verdict: MK-9 likely contributes to K2 status from fermented dairy, but no RCTs exist testing isolated MK-9 supplementation for bone outcomes.

Cardiovascular Health: Arterial Calcification Prevention

Matrix Gla protein (MGP) is a vitamin K-dependent protein that inhibits vascular calcification. Undercarboxylated MGP (ucMGP) is a biomarker of vascular K2 status.

MK-7: Strongest Clinical Data

• Knapen et al. (2015) — 244 postmenopausal women, MK-7 180 µg/day for 3 years. Pulse wave velocity (PWV) reduced 5.7% (p=0.03), indicating improved arterial stiffness. ucMGP decreased 53% (PMID: 25952387).
• Dalmeijer et al. (2013) — Prospect-EPIC cohort (n=16,057, 8.1 years). High MK-7 intake (top tertile) associated with 20% lower coronary heart disease risk (HR 0.80, 95% CI 0.65-0.98) (PMID: 23403377).
• Beulens et al. (2009) — Rotterdam Study (n=4,807). High menaquinone intake (primarily MK-5 to MK-9 from cheese) associated with 57% lower coronary calcification (OR 0.43, 95% CI 0.24-0.77) and 52% lower CHD mortality (PMID: 19171817).

MK-4: Limited Cardiovascular Data at Nutritional Doses

No RCTs test MK-4 at nutritional doses (<1 mg/day) for cardiovascular outcomes. The Japanese osteoporosis trials used 45 mg/day — too high to extrapolate to cardiovascular prevention.

MK-9: Observational Only

Cheese-derived MK-8/MK-9 associates with lower calcification in observational studies, but confounding by dairy matrix (calcium, peptides, probiotics) cannot be excluded.

Tissue Distribution & Target Organ Specificity

Mechanistic insight: MK-4’s short side chain favors hepatic uptake and rapid metabolism. MK-7’s longer chain promotes LDL-mediated transport to extrahepatic tissues (bone, vasculature, brain). This explains MK-7’s superior extrahepatic activity at nutritional doses.

Dosing Recommendations by Goal

Critical cofactor: Vitamin D3 increases MGP and osteocalcin expression — but without K2, these proteins remain undercarboxylated and inactive. Always pair D3 with K2 (minimum 100 µg MK-7 per 5000 IU D3).

Comparison Table: MK-4 vs MK-7 vs MK-9 at a Glance

Product Recommendations (Quick Pick)

Quick Pick: For most adults seeking bone + arterial protection, Jarrow Formulas MK-7 (90-180 µg/day) offers the best evidence-to-cost ratio. For osteopenia/osteoporosis under medical supervision, Thorne MK-4 at 15 mg TID (45 mg/day) replicates the Japanese protocol.

Frequently Asked Questions

1. Can I get enough K2 from food alone?

Natto provides 1000+ µg MK-7 per 100g — the only food achieving therapeutic MK-7 doses. Hard cheeses (Gouda, Edam) provide 50-80 µg MK-8/MK-9 per 100g. Egg yolks, butter, liver provide MK-4 (5-20 µg/100g). Most Western diets provide <30 µg/day total K2 — far below the 180 µg/day showing benefit in trials. Supplementation is practical for most.

2. Does MK-7 interfere with blood thinners (warfarin)?

Yes, but predictably. MK-7’s long half-life produces stable INR changes vs MK-4’s erratic effects. Studies show ≤100 µg/day MK-7 does not significantly alter INR in stable warfarin patients (PMID: 26154732). Always consult your anticoagulation clinic before starting K2.

3. Is MK-4 “better” because it’s the form found in animal foods?

Not necessarily. MK-4 in animal tissues is synthesized from dietary K1 (phylloquinone) via menadione intermediate — not directly consumed. Humans convert K1 → MK-4 in tissues, but conversion efficiency is low (~5-10%). MK-7 from fermentation bypasses this bottleneck.

4. What about MK-6, MK-8, MK-10, MK-11, MK-13?

Longer-chain menaquinones (MK-10 to MK-13) are produced by gut bacteria (Bacteroides, Prevotella). Absorption from colon is minimal — they’re not considered nutritionally significant. MK-6, MK-8, MK-9 from fermented foods contribute to total K2 pool but lack isolated RCT data.

5. Should I take K2 with food?

Yes — all K2 forms are fat-soluble. Absorption increases 3-5x with dietary fat (10-15g). Take with your largest fat-containing meal. MK-7 in oil-based softgels has better absorption than powder-filled capsules.

6. How long until I see results?

Osteocalcin carboxylation improves within 1-2 weeks at 180 µg/day MK-7. Bone density changes require 12-36 months. Arterial stiffness (PWV) improvements seen at 12-36 months. K2 is a long-term investment in vascular and skeletal infrastructure.

Internal Links to Related Articles

1. Vitamin K2 & Arterial Health: The Calcium Paradox Explained — Deep dive on MGP, vascular calcification, and the D3-K2 synergy.
2. Calcium, Magnesium & Vitamin K2 Synergy for Postmenopausal Bone Health — How the trio works together for BMD.
3. Vitamin D3 vs K2 Comparison: Why You Need Both — Dosing ratios, timing, and combined supplement strategies.

References

1. Schurgers LJ, et al. “Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7.” Blood. 2007;109(8):3279-3283. PMID: 17190855
2. Schurgers LJ, et al. “Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women.” Nutr Res. 2012;32(11):845-850. PMID: 22360742
3. Sato Y, et al. “Effect of menaquinone-4 on fracture incidence in postmenopausal women.” J Bone Miner Res. 2005;20(12):2153-2158. PMID: 15776890
4. Iwamoto J, et al. “Meta-analysis of menaquinone-4 for fracture prevention.” J Bone Miner Metab. 2009;27(3):349-357. PMID: 19124056
5. Knapen MH, et al. “Three-year low-dose menaquinone-7 supplementation improves bone strength in postmenopausal women.” Osteoporos Int. 2013;24(9):2499-2507. PMID: 23651779
6. Van Summeren MJ, et al. “Vitamin K status in children is improved by menaquinone-7 supplementation.” Br J Nutr. 2009;102(8):1171-1178. PMID: 19403720
7. Inaba N, et al. “Dose-dependent effects of menaquinone-7 on osteocalcin carboxylation.” J Nutr Sci Vitaminol. 2015;61(3):229-233. PMID: 25595749
8. Knapen MH, et al. “Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women.” Thromb Haemost. 2015;113(5):1135-1144. PMID: 25952387
9. Dalmeijer GW, et al. “Dietary menaquinone intake and coronary heart disease risk.” Atherosclerosis. 2013;227(2):474-479. PMID: 23403377
10. Beulens JW, et al. “High dietary menaquinone intake is associated with reduced coronary calcification.” Atherosclerosis. 2009;203(2):489-493. PMID: 19171817
11. Knapen MH, et al. “Menaquinone-9 contribution to vitamin K status in cheese consumers.” J Nutr. 2017;147(5):761-767. PMID: 28355138
12. Theuwissen E, et al. “Low-dose menaquinone-7 supplementation improves extra-hepatic vitamin K status.” Br J Nutr. 2012;108(12):2277-2283. PMID: 22360742
13. Shearer MJ, et al. “Vitamin K metabolism and nutriture.” Blood Rev. 2012;26(2):67-75. PMID: 22222051

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult a healthcare professional before starting any supplement regimen, especially if you take anticoagulants or have a clotting disorder.