What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
Vitamin K1 benefits: where the science stands
For bone: not settled yet.
Bone is what most people take vitamin K1 for, and the best studies disagree: one found it helps, five found no effect. As of August 2026, the verdicts on this page rest on evidence from 46 trials, drawn from the strongest research among the 303 papers on PubMed that mention vitamin K1. Every claim is checked below.
303 papers on PubMed · evidence from 46 trials · 1 caution
Claim by claim
- BoneThe science is still forming. The best studies disagree.
- Blood pressureThe science is still forming. No real difference found so far.
- Blood sugarThe science is still forming. The best studies disagree.
- CholesterolThe science is still forming. A safety question was raised; later testing found no change.
See 4 more scored claims+
- Eye healthAlmost no real studies. What exists leans positive.
- HeartThe science is still forming. The best studies disagree.
- InflammationThe science is still forming. No real difference found so far.
- JointsThe science is still forming. No real difference found so far.
Pairs people ask about
The 22 sources we read
- 2004Randomized trial · 108 people · benefit for heartsource
- 2006Meta-analysis · pools 13 trials · benefit for bonesource
- 2008Randomized trial · 452 people · no clear effect on bonesource
- 2008Randomized trial · 14 people · no clear effect on bonesource
- 2008Randomized trial · 355 people · no clear effect on blood sugarsource
- 2008Crossover trial · 31 people · a harm signal on cholesterol; no clear effect on inflammationsource
- 2008Randomized trial · 378 people · no clear effect on jointssource
- 2009Randomized trial · 388 people · no clear effect on heartsource
- 2010Observational study · no clear effect on heartsource
- 2010Randomized trial · 42 people · no clear effect on blood sugarsource
- 2013Observational study · 857 people · no clear effect on heartsource
- 2014Randomized trial · 86 people · no clear effect on bonesource
- 2015Randomized trial · 82 people · moderate benefit for blood sugarsource
- 2016Randomized trial · 64 people · no clear effect on jointssource
- 2017Observational study · 5,860 people · benefit for eye healthsource
- 2019Meta-analysis · no clear effect on blood pressuresource
- 2020Meta-analysis · pools 9 trials · no clear effect on heartsource
- 2021Meta-analysis · no clear effect on bonesource
- 2022Randomized trial · 149 people · benefit for heartsource
- 2023Randomized trial · 105 people · no clear effect on bonesource
- 2024Meta-analysis · no clear effect on blood sugar; no clear effect on cholesterol; no clear effect on inflammationsource
- 2026Meta-analysis · pools 8 trials · small benefit for blood sugarsource
Chosen as the strongest evidence out of 303 papers on PubMed. Every row links to its paper.
Fair questions
Does vitamin K1 work?+
For bone, it is not settled. The best studies disagree.
Is vitamin K1 safe?+
One caution is recorded: Searching 21 health outcomes returned no trial of vitamin K1 on its own for any of them. This is not the same as a supplement nobody has studied. Vitamin K1 is a nutrient your body needs, and there is research on it. What that research is about is its interaction with the blood thinner warfarin, and combinations of vitamin K with vitamin D where the two cannot be separated. None of it tells you whether taking extra helps someone who already gets enough.
Why only 22 sources, when PubMed lists 303?+
The 303 is every paper that mentions vitamin K1 in any way: animal studies, blood measurements, papers where it is a side note. The strongest sources are combined reviews, and each one already gathers every trial its authors could find. Our 22 cover 46 trials between them, and every one is linked above. Both counts are measured, not estimated.