Vitamin K

Does vitamin K help keep bones strong?

Updated 3 Nov 2026

Short answer

Not clearly. A 2019 review of 36 trials found no evidence of an effect on bone density or spine fractures in women after menopause or people with osteoporosis.[1] The odds of any clinical fracture were 28% lower with vitamin K, but in the trials with a low risk of bias this result could be due to chance.[1] One trial in healthy women after menopause found slower bone loss with 180 µg of MK-7 a day for 3 years.[2]

What the reviews found

A 2006 review pooled 7 trials from Japan, all of MK-4, most at 45 mg a day. It found fewer spine, hip and other fractures with MK-4.[3][4]

A 2019 update pooled 36 trials. It noted that the integrity of some of the earlier evidence had been questioned.[1] Its results for women after menopause and people with osteoporosis:[1]

  • Any clinical fracture. The odds were 28% lower with vitamin K (odds ratio 0.72). In the trials with a low risk of bias they were 24% lower, and this result could be due to chance.[1]
  • Spine fractures. No difference (odds ratio 0.96).[1]
  • Bone density of the spine. 1.63% higher after 2 years. Without the trials at high risk of bias, the difference became smaller and could be due to chance.[1]

The review concluded that there is no evidence that vitamin K changes bone density or spine fractures. It may lower clinical fractures, but the evidence is not enough to confirm this.[1]

A 2022 review of 16 trials of vitamin K2 in 6,425 women after menopause found a higher bone density at the spine. In the 6 trials that counted fractures, the risk did not differ (risk ratio 0.96).[5]

Single trials

  • 244 healthy women after menopause took 180 µg of MK-7 or a placebo every day for 3 years. MK-7 slowed the loss of bone at the spine and the femoral neck (the top of the thigh bone), but not at the whole hip.[2]
  • 381 healthy North American women after menopause took 1 mg of vitamin K1, 45 mg of MK-4 or a placebo for 12 months. Everyone also got calcium and vitamin D. Bone density did not differ between the groups.[6]
  • 452 men and women aged 60 to 80 took a multivitamin with or without 500 µg of vitamin K1 for 3 years, with calcium and vitamin D. Bone density did not differ.[7]
  • 440 women after menopause with low bone density took 5 mg of vitamin K1 or a placebo for 2 to 4 years. Bone density did not differ. Fewer women in the vitamin K group had a clinical fracture (9 against 20), but the trial was not large enough to study fractures, and the numbers were small.[8]

Why it may work

  1. Osteocalcin is one of the main proteins in bone.[4]
  2. Vitamin K helps an enzyme to finish osteocalcin by a chemical step called carboxylation, which makes the protein active.[4][9]
  3. In some studies, people with more unfinished (undercarboxylated) osteocalcin in the blood had lower bone density.[4]
  4. In three of the trials above, vitamin K lowered unfinished osteocalcin, but bone density did not differ from the control group.[6][7][8]

Why the results differ

  • All 7 fracture trials in the 2006 review were from Japan and used MK-4.[3] In Japan, 45 mg of MK-4 a day is a medicine for osteoporosis.[4]
  • In some trials, only the vitamin K group also got vitamin D or calcium. Part of the effect may then come from vitamin D or calcium.[4]
  • The European Food Safety Authority approved a health claim that vitamin K helps keep bones normal. The US FDA has not authorized a health claim for vitamin K.[4]

Who should be careful

Vitamin K changes the effect of warfarin and similar blood thinners. People who take them should ask a doctor or pharmacist before they start vitamin K.[4]

Sources (9)

  1. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Mott A, Bradley T, Wright K, Cockayne ES, Shearer MJ, Adamson J, et al. Osteoporos Int, 2019. PMID 31076817
  2. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Knapen MH, Drummen NE, Smit E, Vermeer C, Theuwissen E Osteoporos Int, 2013. PMID 23525894
  3. Vitamin K and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials. Cockayne S, Adamson J, Lanham-New S, Shearer MJ, Gilbody S, Torgerson DJ Arch Intern Med, 2006. PMID 16801507
  4. Vitamin K: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  5. Efficacy of vitamin K2 in the prevention and treatment of postmenopausal osteoporosis: A systematic review and meta-analysis of randomized controlled trials. Ma ML, Ma ZJ, He YL, Sun H, Yang B, Ruan BJ, et al. Front Public Health, 2022. PMID 36033779
  6. Vitamin K treatment reduces undercarboxylated osteocalcin but does not alter bone turnover, density, or geometry in healthy postmenopausal North American women. Binkley N, Harke J, Krueger D, Engelke J, Vallarta-Ast N, Gemar D, et al. J Bone Miner Res, 2009. PMID 19113922
  7. Effect of vitamin K supplementation on bone loss in elderly men and women. Booth SL, Dallal G, Shea MK, Gundberg C, Peterson JW, Dawson-Hughes B J Clin Endocrinol Metab, 2008. PMID 18252784
  8. Vitamin K supplementation in postmenopausal women with osteopenia (ECKO trial): a randomized controlled trial. Cheung AM, Tile L, Lee Y, Tomlinson G, Hawker G, Scher J, et al. PLoS Med, 2008. PMID 18922041
  9. Dietary reference values for vitamin K. European Food Safety Authority, 2017. efsa.onlinelibrary.wiley.com

More about vitamin k

What is vitamin K?Which foods contain vitamin K?What is vitamin K used for?Who is at risk of vitamin K deficiency?Is vitamin K safe?Why do newborn babies get vitamin K?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.