Vitamin K, vitamin D and bone health
What it found
Vitamin K helps activate proteins that move calcium into bone, and taking it alongside vitamin D may support bone strength, especially in older women.
The evidence comes from a mix of population studies, trials in people and lab work.
What they found
Studies in people
Bone density and fractures
In the U.S. Nurses' Health Study, more than 72,000 women were followed for 10 years. Women who took in less than 109 micrograms of vitamin K1 a day had a 30% higher risk of hip fracture than those who took in at least that much.
Vitamin K2 supplements
A meta-analysis of 16 randomized trials in postmenopausal women found that vitamin K2 supplements improved lumbar spine bone mineral density in 10 studies. In subgroup analysis, only K2 given with other remedies had a significant effect. K2 also reduced fracture risk in five studies.
Combining K and D
A 2020 meta-analysis of eight randomized trials with 971 participants concluded that vitamin K combined with vitamin D3 significantly increased total bone mineral density. A three-year trial in 142 postmenopausal women with osteopenia found the combination increased carboxylation of osteocalcin compared with placebo.
Vitamin K status marker
A low ratio of carboxylated to undercarboxylated osteocalcin, or a high level of undercarboxylated osteocalcin, indicates poor vitamin K status. This has been linked to bone loss and higher risk of hip fracture.
Animal and lab studies
Animal and lab studies
In a rat study, vitamin K supplementation improved bone characteristics more than combined calcium and vitamin D in a model of immobilization osteoporosis. In an animal model of obesity, MK-4 promoted bone formation by influencing activated osteocalcin and osteoprotegerin levels while reducing RANKL.
Other findings
Vitamin K activates proteins
Vitamin K is needed to activate osteocalcin and matrix Gla-protein. Once activated, these proteins can bind calcium and help move it from the blood into bone.
What the authors conclude
“An adequate supply of vitamin K, on top of an optimal vitamin D status, seems to add to the benefit of maintaining bone health.”
Also in their conclusions
- They conclude that there is extensive evidence for a positive effect of adequate vitamin K status and vitamin K2 supplementation on osteocalcin carboxylation and bone health.
- They advise that further research is needed on the mechanisms of different vitamin K forms to establish vitamin K2 as a safe and cost-effective supplement for preventing osteoporosis.
- They state that a combined regimen including vitamin K might benefit prevention of osteoporosis after bariatric surgery, but for treating osteoporosis, drugs such as bisphosphonates or denosumab will still be essential.
How it was done
The authors wanted to review recent data on how vitamin K deficiency, and combined vitamin K and D deficiency, relate to osteoporosis, and to discuss the mechanisms behind these links.
They searched PubMed, Medline and Google Scholar for English-language papers published between 2000 and 2023 using the keywords vitamin K, vitamin D, and osteoporosis or bone mineral density. They also included their own research.
What it can’t tell you
- Most supplement studies used vitamin K2, often at high doses far above nutritional needs, so little is known about vitamin K1 supplements.
- Observational studies can show a link between vitamin K intake and fracture risk, but they cannot prove that vitamin K directly causes the difference.
- The authors note that more research is needed on the long-term effects of combined vitamin K and vitamin D3 supplementation.
Who paid
- Funding
- Funded by Innlandet Hospital Trust (from the PubMed record).
- Conflicts
- The authors declare that they have no conflicts of interest.
- Authors work at
- Innlandet Hospital Trust, Norway; Inland Norway University of Applied Sciences, Norway; Innlandet Hospital Hamar, Norway
The paper
- Title
- The Importance of Vitamin K and the Combination of Vitamins K and D for Calcium Metabolism and Bone Health: A Review
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Aaseth JO, Finnes TE, Askim M, Alexander J (2024). The Importance of Vitamin K and the Combination of Vitamins K and D for Calcium Metabolism and Bone Health: A Review. Nutrients. doi:10.3390/nu16152420Free full textPubMed 39125301DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error