Vitamin K2
A 2006 review of Japanese MK-4 trials found large fracture reductions. A 2019 update found no effect on vertebral fractures or bone density, and only a possible drop in clinical fractures. Coronary calcium grew more slowly on K2 in two trials, but valve calcium did not change in a third. Doses as low as 10 µg changed anticoagulant control.
Add to Bio HackChecked 2026-11-09
- Status
- Dietary supplement in the US.
- Also called
- menaquinone, MK-4, MK-7, menatetrenone, menaquinone-7, vitamin K, natto extract, K2 with D3
- Taken for
- bone density, fracture prevention, artery calcification, heart health, calcium metabolism, taking with vitamin D
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help0
No benefit shown in research yet.
Reported risks1
What people take it for, and what was found
Mixed results3
Fractures
Limited evidence: older Japanese trials found fewer fractures, but a 2019 update found no difference in spine fractures and no significant effect in low-bias trials.
The numbers and sources
- Effect
- Sources disagree. A 2006 meta-analysis of 7 Japanese MK-4 trials found lower odds of vertebral fractures (OR 0.40, 95% CI 0.25 to 0.65), hip fractures (OR 0.23, 95% CI 0.12 to 0.47) and all nonvertebral fractures (OR 0.19, 95% CI 0.11 to 0.35) [1]. A 2019 update found no difference in vertebral fractures (OR 0.96, 95% CI 0.83 to 1.11). Any clinical fracture was lower (OR 0.72, 95% CI 0.55 to 0.95), but in low-bias trials the difference was not significant (OR 0.76, 95% CI 0.58 to 1.01) [2].
- Population
- Japanese patients in all 7 fracture trials [1]; postmenopausal or osteoporotic adults in 36 studies [2].
- Sources
- [1], [2]
- Caveats
- The 2019 authors write that the integrity of some earlier evidence had been questioned since the 2006 review [2]. Both reviews pooled vitamin K1 and K2 trials for bone density.
Bone mineral density
Limited evidence: spine density gains vanished after removing high-bias trials. One 3-year trial found slower bone loss in postmenopausal women.
The numbers and sources
- Effect
- Pooled lumbar spine density was 1.63% higher at 2 years (95% CI 0.10 to 3.16), but removing high-bias trials made the differences smaller and not significant. The 2019 authors conclude there is no evidence of an effect on bone density in postmenopausal or osteoporotic patients [2]. In one 3-year trial, 180 µg of MK-7 a day slowed the age-related loss of density at the lumbar spine and femoral neck, not the total hip [3].
- Population
- Postmenopausal or osteoporotic adults [2]; 244 healthy postmenopausal women in the Netherlands [3].
- Sources
- [2], [3]
- Caveats
- The MK-7 trial abstract gives no effect sizes [3]. Too few trials in men or other groups for conclusions [2].
Artery and valve calcification
Small trials found mixed results: vitamin K slowed artery calcification in some trials but not valve calcification in men. Calcification is a scan marker.
The numbers and sources
- Effect
- Across 13 controlled trials (2,162 people), vitamin K reduced vascular calcification by 9.1% (95% CI 0.5 to 17.7) against control, with no significant change in arterial stiffness [4]. Over 2 years, coronary calcium scores rose from a median 145 to 214 on placebo and from 135 to 184 on 360 µg MK-7 a day, a significant difference [5]. In men with aortic valve calcification, 720 µg MK-7 plus vitamin D for 2 years did not change valve calcium progression (difference 17 units, 95% CI -86 to 53) or aortic and coronary calcium [6]. In 398 people with severe coronary calcification, 720 µg vitamin K2 plus 25 µg vitamin D a day for 24 months slowed the rise in calcium score (196 against 248 units, difference -52, 95% CI -79 to -24). Total plaque volume rose similarly in both groups [7].
- Population
- 13 controlled trials with 2,162 participants [4]; 180 Dutch patients with symptomatic coronary disease [5]; 365 men from the community averaging 71 years [6]; 398 adults with a calcium score of 400 or more, median age 71 [7].
- Sources
- [4], [5], [6], [7]
- Caveats
- Calcification is a scan marker, not heart attack or death. The meta-analysis notes few studies and substantial heterogeneity [4]. The valve trial was funded by the Novo Nordisk Foundation [6]. The two 720 µg trials gave vitamin D with vitamin K2 [6][7].
Not shown to help1
Heart attack, stroke and cardiovascular death
One small trial found no difference in heart events or deaths, with far too few events to test an effect.
The numbers and sources
- Effect
- In the valve trial, cardiovascular events (10 against 10) and deaths (1 against 4) did not differ between MK-7 plus vitamin D and placebo [6].
- Population
- 365 men with aortic valve calcification, 24 months [6].
- Sources
- [6]
- Caveats
- Clinical events were safety outcomes in a small trial, far too few to test an effect.
Doses studied
The bone trial used 180 µg of MK-7 a day for 3 years [3]. The coronary trials used 360 µg a day [5] and 720 µg a day with 25 µg vitamin D [7], and the valve trial 720 µg a day with 25 µg vitamin D [6]. The anticoagulant study gave 10, 20 and 45 µg a day in rising steps [8]. The Japanese fracture trials used MK-4 [1]. EFSA found no adequate data to derive a tolerable upper intake level for vitamin K [9].
Risks
Reported risks1
Interference with warfarin-type anticoagulants
One small study found 45 µg of K2 a day lowered INR, a measure of blood thinning, about 40% in healthy adults on acenocoumarol, a warfarin-type drug.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In volunteers anticoagulated with acenocoumarol, 45 µg of MK-7 a day lowered the group INR by about 40%. At 10 and 20 µg a day, two hematologists independently judged the INR drop clinically relevant in at least 40% and 60% of subjects [8].
- Population
- 18 healthy men and women, 15 of whom reached a target INR of 2.0, over 6 weeks of MK-7 [8].
- Sources
- [8]
- Caveats
- A small study in healthy volunteers on acenocoumarol, a drug in the same class as warfarin. It did not test direct oral anticoagulants.
Checked, no increase found1
Adverse events in trials
Small trials found no significant adverse effects over 2 years.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- No significant adverse effects were observed over 2 years at 360 µg a day [5]. In the valve trial, deaths and cardiovascular events did not differ from placebo [6].
- Population
- 167 analyzed patients [5]; 365 men [6].
- Sources
- [5], [6]
- Caveats
- Small trials with few events.
Claims tested and not found
Sources
- Cockayne S, Adamson J, Lanham-New S, et al. Vitamin K and the Prevention of Fractures. Archives of Internal Medicine. 2006. https://doi.org/10.1001/archinte.166.12.1256
- Mott A, Bradley T, Wright K, et al. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Osteoporosis International. 2019. https://doi.org/10.1007/s00198-019-04949-0
- Knapen MHJ, Drummen NE, Smit E, et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International. 2013. https://doi.org/10.1007/s00198-013-2325-6
- Lees JS, Chapman FA, Witham MD, et al. Vitamin K status, supplementation and vascular disease: a systematic review and meta-analysis. Heart. 2019. https://doi.org/10.1136/heartjnl-2018-313955
- Vossen LM, de Leeuw PW, Schurgers LJ, et al. Two Years of Menaquinone-7 Supplementation and Coronary Artery Calcification. JAMA Cardiology. 2026. https://doi.org/10.1001/jamacardio.2026.1279
- Diederichsen AC, Lindholt JS, Möller S, et al. Vitamin K2 and D in Patients With Aortic Valve Calcification: A Randomized Double-Blinded Clinical Trial. Circulation. 2022. https://doi.org/10.1161/circulationaha.121.057008
- Hasific S, Øvrehus KA, Mejldal A, et al. Vitamin K2 and D3 Supplementation in Patients With Severe Coronary Artery Calcification: The DANCODE Trial. Circulation. 2026. https://doi.org/10.1161/CIRCULATIONAHA.126.082363
- Theuwissen E, Teunissen K, Spronk H, et al. Effect of low-dose supplements of menaquinone-7 (vitamin K2) on the stability of oral anticoagulant treatment: dose-response relationship in healthy volunteers. Journal of Thrombosis and Haemostasis. 2013. https://doi.org/10.1111/jth.12203
- European Food Safety Authority. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Version 11. 2025. https://www.efsa.europa.eu/sites/default/files/assets/UL_Summary_tables.pdf