As a product formulator here at New Chapter, I notice that vitamin K gets skipped in some typical multivitamins, especially gummies and liquids. Maybe it’s not a sexy vitamin, but there are a lot of fascinating, evidence-based benefits that might make you look at K in a whole new way.
What is Vitamin K?
The term “Vitamin K” encompasses a larger group of fat-soluble compounds, all sharing a similar chemical structure. First there is Vitamin K1 (phylloquinone), the most common food-form found in green leafy vegetables and certain plant oils. Then there are the Vitamin K2s, which live in a family of about ten compounds called menaquinones that differ based on the length of their molecular side chain, varying from 4 to 13 units long (menaquinone-4 to menaquinone-13). The most common forms you will see are menaquinone-4 (MK-4) which is typically found in meat and dairy products, and menaquinone-7 (MK-7) produced by bacteria in foods like natto and some cheeses.1–4
How does Vitamin K work?
Regardless of the form, they all play a lead role as a cofactor in the enzymatic gamma-carboxylation of vitamin K-dependent proteins. To break that down a little bit:
- Vitamin K-dependent proteins are molecules in the body that require vitamin K to function properly by helping them hold onto calcium ions.
- These proteins are “activated” by an enzyme (called γ-glutamylcarboxylase) that helps add a particular molecular structure (a carboxyl group) to the protein.
- Specifically, it supports converting the amino acid glutamic acid (Glu) to γ-carboxyglutamic acid (Gla).
- That enzyme requires vitamin K to do its job of adding the carboxyl group and converting Glu to Gla.
- Without vitamin K, the enzyme cannot activate the protein, and the protein cannot effectively do its job.
What are the benefits of Vitamin K?
So how does all that translate to physical functions in the body? There are essential vitamin K dependent proteins in following systems:
Vitamin K Helps Blood Clotting
When a bleed starts in the body, there is an intricate series of steps called the “coagulation cascade” involving various proteins called “clotting factors”. Many of these proteins (such as factors II (prothrombin), VII, IX, and X) require vitamin K to become functional via the carboxylation process described above. In fact, blocking the action of vitamin K with vitamin K antagonists is one strategy used in medicine to prevent blood from clotting/coagulating because it prevents the vitamin K-dependent γ-carboxylation reactions from taking place.3,5 An example of this blocking action is the blood thinner medication that some people take when managing certain cardiovascular conditions.
Vitamin K Supports Bone Formation
Several bone-related proteins require vitamin K-dependent γ-carboxylation to function properly, such as osteocalcin, matrix Gla protein (MGP), Gla-rich protein (GRP), and periostin. Osteocalcin is one of the more prominent proteins, with a well-known role in multiple systems, including bone mineralization, glucose modulation, brain development, and male fertility. It is synthesized by osteoblasts (the primary bone-building cells in the body), and as part of its creation, three glutamate (Glu) residues are carboxylated to form γ-carboxyglutamic acid (Gla) residues. These Gla residues enable the protein to strongly bind calcium ions, a property essential for its role in regulating hydroxyapatite (the main bone mineral) formation during bone remodeling.6,7 In short, vitamin K helps turn on proteins that allow calcium to be used where it belongs, supporting healthy bone building.
Vitamin K Promotes Vascular Health
Matrix Gla Protein (MGP) is another vitamin K-dependent protein that has been found in cartilage, bone, and other soft tissues (such as blood vessel walls), and plays a central role in preventing mineralization. Carboxylated (active) MGP binds directly to calcium crystals and suppresses their growth. Low vitamin K can result in reduced levels of active MGP and therefore a reduction in that mineral-binding capacity, increasing chances of vascular calcification and cartilage mineralization.8,9 In fact, inactive circulating MGP is used as a marker of poor vitamin K status and is linked to higher risk of vascular calcification. Put simply, vitamin K is part of your biological systems that help keep blood vessels healthy, clear, and flexible.
Beyond these well-established roles, vitamin K has also gained attention for its involvement in broader metabolic, neurologic and antioxidant, and inflammatory pathways.10,11 For instance, the vitamin K-dependent protein Gas6 is readily found in brain tissues where it’s known for regulating inflammatory and immune pathways.12 Also, vitamin K in its reduced form has been shown directly uptake reactive oxygen species (unstable molecules that can damage cells), thereby protecting cell membranes from peroxidation.13,14 These are just a couple of the many proposed reasons for why vitamin K2 levels in the brain have been associated with better cognitive status in older adults.15
How Vitamin K Forms Differ: K1, K2, MK-4 and MK-7
While it might not be intuitive, of all the forms of vitamin K, vitamin K1 from plants has the poorest absorption. It’s tightly bound to plant tissues and not readily released during digestion or cooking. Isolated K1 is better, but the body tends to clear K1 from the blood fairly quickly (it has a short half-life of just a few hours).5 In contrast, certain K2 forms—especially the longer-chain menaquinones—remain in circulation much longer.4,16,17 MK-7 specifically has a half-life in the range of days, allowing it to be distributed more widely to extra-hepatic (outside the liver) tissues such as bone and blood vessels. This means MK-7 can be more available to support carboxylation of proteins beyond the liver (like osteocalcin and MGP in bone and arteries).2 For all forms, it is generally advisable to consume them with fats or oils in a meal to help with their absorption.
Because of its inherently longer half-life, MK-7 is generally considered to have higher bioavailability compared to K1 or MK-4. In supplementation trials, MK-7 has been shown to more completely carboxylate osteocalcin than an equivalent amount of K1.18 Another clinical study where participants received either MK-4 or MK-7 showed that MK-7 was well absorbed and reached maximal serum level at 6 h after intake and was detected up to 48 h after intake. At the same time, for those who received MK-4, it was generally not detectable in the serum at any time point.18,19
Here’s a simple way to think about the different forms of vitamin K:
| Form | What it is | Where it's commonly found | What to know |
|---|---|---|---|
| Vitamin K1 (phylloquinone) | Plant form of vitamin K | Leafy green vegetables | An essential and important nutrient, but less well absorbed and clears quickly from the bloodstream |
| Vitamin K2 (menaquinones) | A group of vitamin K forms | Fermented foods and supplements | Stays active in the body longer than K1 |
| MK 4 | Short chain form of K2 | Animal foods; some supplements | Clears quickly from the blood and is often harder to detect after intake |
| MK‑7 | Long chain form of K2 | Fermented foods and supplements | Remains in circulation for days, making it more available to support bones and blood vessels |
The Power of K
1. Linus Pauling Institute, O. S. U. Vitamin K. https://lpi.oregonstate.edu/mic/vitamins/vitamin-K (2014).
2. Rodríguez-Olleros Rodríguez, C. & Díaz Curiel, M. Vitamin K and Bone Health: A Review on the Effects of Vitamin K Deficiency and Supplementation and the Effect of Non-Vitamin K Antagonist Oral Anticoagulants on Different Bone Parameters. J. Osteoporos. 2019, 2069176 (2019).
3. Office of Dietary Supplements, N. I. of H. Vitamin K. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/.
4. Mladenka, P. et al. Vitamin K – sources, physiological role, kinetics, deficiency, detection, therapeutic use, and toxicity. Nutr. Rev. 80, 677–698.
5. Xiao, H., Chen, J., Duan, L. & Li, S. Role of emerging vitamin K‑dependent proteins: Growth arrest‑specific protein 6, Gla‑rich protein and periostin (Review). Int. J. Mol. Med. 47, 1–1 (2021).
6. Karsenty, G. Osteocalcin: A Multifaceted Bone-Derived Hormone. Annu. Rev. Nutr. 43, 55–71 (2023).
7. Gundberg, C. M., Lian, J. B. & Booth, S. L. Vitamin K-Dependent Carboxylation of Osteocalcin: Friend or Foe? Adv. Nutr. 3, 149–157 (2012).
8. Schurgers, L. J. et al. Post‐translational modifications regulate matrix Gla protein function: importance for inhibition of vascular smooth muscle cell calcification. J. Thromb. Haemost. 5, 2503–2511 (2007).
9. Gheduzzi, D. et al. Matrix Gla protein is involved in elastic fiber calcification in the dermis of pseudoxanthoma elasticum patients. Lab. Invest. 87, 998–1008 (2007).
10. Ahmed, S. R., Mokgalaboni, K. & Phoswa, W. N. The Differential Effects of Vitamin K Across Glycaemic Outcomes in Prediabetes and Type 2 Diabetes Mellitus. Nutrients 18, 269 (2026).
11. Diachenko, A. I., Rodin, I. A., Krasnova, T. N., Klychnikov, O. I. & Nefedova, L. N. The Role of Vitamin K in the Development of Neurodegenerative Diseases. Biochem. Mosc. 89, S57–S70 (2024).
12. Aydin, N., Ouliass, B., Ferland, G. & Hafizi, S. Modification of Gas6 Protein in the Brain by a Functional Endogenous Tissue Vitamin K Cycle. Cells 13, 873 (2024).
13. Vervoort, L. M. T., Ronden, J. E. & Thijssen, H. H. W. The potent antioxidant activity of the vitamin K cycle in microsomal lipid peroxidation. Biochem. Pharmacol. 54, 871–876 (1997).
14. Simes, D. C., Viegas, C. S. B., Araújo, N. & Marreiros, C. Vitamin K as a Diet Supplement with Impact in Human Health: Current Evidence in Age-Related Diseases. Nutrients 12, (2020).
15. Booth, S. L. et al. Association of vitamin K with cognitive decline and neuropathology in community-dwelling older persons. Alzheimers Dement. 8, e12255 (2022).
16. Gijsbers, B. L., Jie, K. S. & Vermeer, C. Effect of food composition on vitamin K absorption in human volunteers. Br. J. Nutr. 76, 223–229 (1996).
17. Schurgers, L. J. & Vermeer, C. Determination of Phylloquinone and Menaquinones in Food: Effect of Food Matrix on Circulating Vitamin K Concentrations. Pathophysiol. Haemost. Thromb. 30, 298–307 (2001).
18. Schurgers, L. J. et al. Vitamin K–containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood 109, 3279–3283 (2007).
19. Sato, T., Schurgers, L. J. & Uenishi, K. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr. J. 11, 93 (2012).
