Researchers studied a special protein called carboxylated osteocalcin that helps bones absorb calcium and stay strong. They looked at bone samples from 45 people undergoing hip surgery and found that people with higher levels of this protein had stronger hip bones. The protein appears to work by helping bones absorb minerals better. While this is interesting, the study was small and looked at people with hip problems, so more research is needed to understand if this applies to everyone and whether vitamin K supplements could help boost this protein.

The Quick Take

  • What they studied: Whether a special bone protein called carboxylated osteocalcin is connected to stronger bones and how it might work
  • Who participated: 45 people who were having hip surgery for arthritis. The researchers excluded people taking medications or with conditions that could affect bone health
  • Key finding: People with higher levels of carboxylated osteocalcin had stronger hip bones, especially thicker cortical bone (the hard outer layer). This connection remained strong even after accounting for age, kidney function, and exercise habits
  • What it means for you: This suggests that a specific form of a bone protein may be important for bone strength, but this is early research. It doesn’t yet mean you should change your diet or take supplements—more studies are needed to confirm these findings and test if increasing this protein actually prevents fractures

The Research Details

This was a cross-sectional study, which means researchers collected information from people at one point in time rather than following them over months or years. The 45 participants were people scheduled for hip surgery due to arthritis. During surgery, doctors collected blood samples and small bone samples from the hip area. The researchers then measured the bone samples using special imaging technology (micro-computed tomography) to look at bone structure in detail, and they used X-ray imaging to measure bone density and strength. They also measured levels of different forms of a bone protein called osteocalcin in the blood samples.

The researchers were specifically interested in carboxylated osteocalcin, which is a special form of the protein that requires vitamin K to be made properly. They compared this form to other versions of the protein that weren’t fully processed. They looked at whether these different forms of the protein were connected to bone structure, bone strength, and markers of bone turnover (signs of how active bone cells are).

The study excluded people taking medications or with medical conditions known to affect bone health, which helps reduce confusing factors. However, because all participants had arthritis and were having surgery, they may not represent healthy people without bone problems.

Understanding how different forms of bone proteins work is important because it could explain why some people have stronger bones than others and why vitamin K supplements don’t always improve bone health in studies. If carboxylated osteocalcin is truly important for bone strength, it might help explain what goes wrong in people with weak bones and could point to new ways to prevent fractures.

This study has some strengths: it measured actual bone tissue directly rather than just using blood tests, it excluded people with conditions that could confuse results, and it used advanced imaging technology. However, it also has limitations: the sample size is small (45 people), all participants had hip arthritis which may not represent healthy people, it’s a one-time snapshot rather than following people over time, and it was done in a hospital setting with people undergoing surgery. These factors mean the results may not apply to everyone.

What the Results Show

The main finding was that people with higher levels of carboxylated osteocalcin had stronger hip bones in multiple ways. Specifically, they had thicker cortical bone (the hard outer shell of bone), larger cross-sectional area (the bone was bigger when sliced), greater cross-sectional moment of inertia (a measure of how well the bone resists bending), wider femoral necks (the narrow part of the thigh bone near the hip), and higher section modulus (another measure of bone strength). All of these connections were statistically significant, meaning they were unlikely to be due to chance.

Interestingly, other forms of the osteocalcin protein that weren’t fully processed (partially or fully un-carboxylated versions) did not show these same connections to bone strength. This suggests that the specific processed form of the protein is what matters for bone strength, not just having the protein in general.

When researchers looked at bone turnover markers (signs of how active bone cells are), they found that carboxylated osteocalcin was connected to higher bone alkaline phosphatase, which is a sign of bone-building activity. The unprocessed forms of the protein were connected to different markers of bone breakdown. This suggests that the processed form of the protein may work by promoting bone building rather than bone breakdown.

The researchers also found that the connection between carboxylated osteocalcin and bone strength remained strong even after accounting for other factors like age, parathyroid hormone levels, kidney function, bone mineral density, and physical activity. This means the protein’s effect appears to be independent of these other factors.

The study found that carboxylated osteocalcin was an independent predictor of bone alkaline phosphatase, suggesting it may influence how actively bone-building cells work. The unprocessed forms of osteocalcin predicted different bone turnover markers (c-terminal telopeptide), suggesting they may be involved in bone breakdown rather than building. These findings suggest that the different forms of the protein may have opposite effects on bone health.

Previous research has shown that vitamin K deficiency is linked to weaker bones and higher fracture risk. However, when researchers have given people vitamin K supplements, the results have been mixed—some studies show improvements in bone health while others don’t. This study helps explain why: vitamin K is needed to make the processed form of osteocalcin (carboxylated osteocalcin), and this specific form appears to be what matters for bone strength. Simply having more of the unprocessed protein may not help. This could explain why some vitamin K supplementation studies haven’t shown clear benefits—they may not have increased the right form of the protein.

This study has several important limitations. First, it’s small with only 45 people, so the results may not apply to larger populations. Second, all participants had hip arthritis and were undergoing surgery, so they don’t represent healthy people without bone problems. Third, it’s a one-time snapshot rather than following people over time, so we can’t know if changes in this protein cause changes in bone strength or if they just happen together. Fourth, the study was done in a hospital setting during surgery, which is not how people normally live. Finally, the study measured bone strength in hip bone specifically, so we don’t know if the same relationship exists in other bones like the spine or wrist.

The Bottom Line

Based on this research, there is not yet enough evidence to recommend specific actions. The findings suggest that carboxylated osteocalcin may be important for bone strength, but this is early research from a small study. If you’re concerned about bone health, current evidence-based recommendations remain: get adequate vitamin K from foods like leafy greens, maintain adequate calcium and vitamin D, do weight-bearing exercise, and avoid smoking. Talk to your doctor before starting any supplements.

This research is most relevant to people concerned about bone health, researchers studying bone biology, and doctors treating osteoporosis or fracture risk. It’s less immediately relevant to healthy young people with no bone concerns. People with hip arthritis or those undergoing hip surgery may find this particularly relevant since the study was done in this population.

This is basic research aimed at understanding how bone proteins work, not a study testing whether an intervention prevents fractures. It will likely take several more years of research before we know if increasing carboxylated osteocalcin through diet, supplements, or other means actually prevents fractures or improves bone health in real people.

Want to Apply This Research?

  • Track vitamin K intake from food sources (leafy greens, broccoli, Brussels sprouts) and note any changes in bone health markers if you have regular bone density scans. Log servings of vitamin K-rich foods daily to ensure adequate intake.
  • Increase consumption of vitamin K-rich foods like spinach, kale, broccoli, and Brussels sprouts. Aim for at least one serving daily. Combine with weight-bearing exercise (walking, strength training) and adequate calcium and vitamin D intake for comprehensive bone health support.
  • If you have regular bone density scans (DEXA scans), track results over time. Monitor dietary vitamin K intake consistently. Note any changes in bone health markers or fracture risk. Discuss results with your healthcare provider to determine if any interventions are needed based on your individual risk factors.

This research is preliminary and was conducted in a small group of people with hip arthritis undergoing surgery. The findings do not yet provide evidence for dietary changes or supplementation recommendations for the general public. This study does not prove that increasing carboxylated osteocalcin prevents fractures or improves bone health in healthy people. Anyone concerned about bone health, at risk for osteoporosis, or considering vitamin K supplementation should consult with their healthcare provider before making changes. This article is for educational purposes and should not be considered medical advice.