Lately, I’ve been getting a lot of questions about vitamin K2. It is increasingly promoted as an important bone health supplement, often alongside calcium and vitamin D. You may have heard that K2 helps direct calcium into the bones rather than allowing it to accumulate in the arteries. It’s an intriguing idea, but is that really what happens? And, more importantly, does taking a K2 supplement actually make our bones stronger and protect our heart? Should those of us concerned about osteoporosis be taking it?
First, What Is Vitamin K2?
Vitamin K is actually a family of compounds. Vitamin K1 (phylloquinone) is found primarily in plants such as leafy greens (collard greens, turnip greens, spinach), broccoli, and soybeans. Vitamin K2 refers to several compounds called menaquinones. They can be found in some animal foods and fermented foods. Some examples include natto, (a traditional Japanese fermented soybean food), aged and fermented cheeses – particularly some hard cheeses – egg yolks, poultry, beef, and pork.
Vitamin K is essential for blood clotting and also activates proteins involved in bone metabolism. One of these is osteocalcin, produced by bone-building cells called osteoblasts. Vitamin K helps activate osteocalcin so that it can bind to the mineral component of bone. But there is an important principle here:
Just because a nutrient is essential for healthy bones doesn’t mean that taking more of it will make your bones stronger.
There is also no separate recommended daily intake for vitamin K2. Current recommendations are based on total vitamin K intake: 90 micrograms per day for adult women and 120 micrograms for adult men (1). Most people in the United States obtain adequate vitamin K from food, and true deficiency is uncommon.
Does Taking K2 Improve Bone Density?
Vitamin K2 supplements commonly contain either MK-4 (menaquinone-4) or MK-7 (menaquinone-7), and you will usually see one of these forms identified on the supplement label. The research exploring the possible connection between supplementing with K2 is mixed. Here is a summary:
A 2013 three-year randomized trial of 244 healthy postmenopausal women found that 180 micrograms of MK-7 daily slowed the age-related decline in some measures of bone density and bone strength (2).
Years later, a three-year trial of 142 women with osteopenia found a different result. Although MK-7 clearly improved the activation of osteocalcin, bone density and bone microarchitecture declined similarly in the K2 and placebo groups (3).
Systematic reviews have produced cautiously encouraging, but inconsistent, results:
A 2022 meta-analysis found possible benefits for lumbar spine bone density, although results differed depending on whether K2 was used alone or with other treatments (4).
A 2025 review found favorable changes in several bone-turnover markers (5). (But changing a laboratory marker is not the same as preventing a fracture, and larger, longer studies are still needed.)
In a study specifically looking at cheese and bone health, researchers found that eating 57 grams (about 2 ounces) of Jarlsberg cheese daily increased vitamin K2 levels and several biochemical markers associated with bone formation (6). However, the trial was small and short-term and did not measure bone density, bone strength, or fractures. The study also received financial support from the manufacturer of Jarlsberg cheese.
You may have read that vitamin K2 – specifically a form called menatetrenone, or MK-4 – has been used as a treatment for osteoporosis in Japan. This is true, but the prescription dose is 45 milligrams per day, far more than the microgram amounts commonly found in over-the-counter K2 supplements. Despite some early encouraging findings, a large, randomized trial did not find a significant reduction in vertebral fractures overall (7). A later systematic review and meta-analysis of this type of treatment found that menatetrenone may improve lumbar-spine bone density and some measures of bone metabolism, but its ability to prevent fractures remains uncertain (8).
Do K2 Supplements Keep Calcium Out of Your Arteries?
There is a biological reason this claim became popular. Vitamin K activates a protein that helps limit calcium deposition in blood vessels and other soft tissues. This has led researchers to investigate whether vitamin K supplements might slow vascular calcification. So far, the answer is possibly, but it hasn’t been proven.
Some meta-analyses have reported slower progression of vascular calcification with vitamin K supplementation, while individual randomized trials have produced inconsistent results (9,10). Vitamin K can affect blood markers involved in calcification, but we do not yet have strong evidence that routinely taking K2 prevents cardiovascular disease.
Should You Take a K2 Supplement?
At this point, I don’t think the evidence supports routinely taking K2 supplements to prevent or treat osteoporosis. The Bone Health and Osteoporosis Foundation reaches essentially the same conclusion – vitamin K is important for bone health, but current research does not support routinely taking vitamin K supplements to prevent osteoporosis or fractures (11).
For most people, a varied diet can provide adequate vitamin K. Food first is almost always the best approach.
One important caution: If you take warfarin (Coumadin), do not start a K2 supplement, or make a major change in your vitamin K intake, without discussing it with your healthcare provider. You do not need to avoid foods containing vitamin K, but consistency is important. Sudden increases or decreases in vitamin K from foods or supplements can alter warfarin’s anticoagulant effect (1).
The Bottom Line
Vitamin K2 has an interesting and biologically plausible role in bone and vascular health. But the evidence has not yet reached the point where most people with osteopenia or osteoporosis should routinely take a K2 supplement. For now, I’d put taking a K2 supplement in the category of promising but not proven.
References
- National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. Bethesda (MD): National Institutes of Health.
- Knapen MHJ, Drummen NE, Smit E, Vermeer C, Theuwissen E. Three-Year Low-Dose Menaquinone-7 Supplementation Helps Decrease Bone Loss in Healthy Postmenopausal Women. Osteoporosis International. 2013;24(9):2499–2507.
- Rønn SH, Harsløf T, Oei L, Pedersen SB, Langdahl BL. The Effect of Vitamin MK-7 on Bone Mineral Density and Microarchitecture in Postmenopausal Women With Osteopenia: A 3-Year Randomized, Placebo-Controlled Clinical Trial. Osteoporosis International. 2021;32(1):185–191.
- Ma ML, Ma ZJ, He YL, Sun H, Yang B, Ruan BJ, Zhan WD, Li SX, Dong H, Wang YX. Efficacy of Vitamin K2 in the Prevention and Treatment of Postmenopausal Osteoporosis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Frontiers in Public Health. 2022 Aug 11;10:979649.
- Zhang Z, Li Y, Li J, Yuan Y, Liu K, Shi X. The Effect of Vitamin K2 Supplementation on Bone Turnover Biochemical Markers in Postmenopausal Osteoporosis Patients: A Systematic Review and Meta-analysis. Frontiers in Endocrinology. 2025;16:1703116.
- Lundberg HE, Glasø M, Chhura R, Shukla AA, Austlid T, Sarwar Z, Hovland K, Iqbal S, Fagertun HE, Holo H, Larsen SE. Effect on Bone Anabolic Markers of Daily Cheese Intake with and without Vitamin K2: A Randomised Clinical Trial. BMJ Nutrition, Prevention, and Health. 2022 Aug 2;5(2):182-190.
- Inoue T, Fujita T, Kishimoto H, et al. Randomized Controlled Study on the Prevention of Osteoporotic Fractures (OF Study): A Phase IV Clinical Study of 15-mg Menatetrenone Capsules. Journal of Bone and Mineral Metabolism. 2009;27(1):66–75.
- Su S, He N, Men P, Song C, Zhai S. The Efficacy and Safety of Menatetrenone in the Management of Osteoporosis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Osteoporosis International. 2019;30(6):1175–1186.
- Li T, Wang Y, Tu WP. Vitamin K Supplementation and Vascular Calcification: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Frontiers in Nutrition. 2023;10:1115069.
- Vlasschaert C, Goss CJ, Pilkey NG, McKeown S, Holden RM. Vitamin K Supplementation for the Prevention of Cardiovascular Disease: Where Is the Evidence? A Systematic Review of Controlled Trials. Nutrients. 2020 Sep 23;12(10):2909.
- Bone Health & Osteoporosis Foundation. Frequently Asked Questions: Nutrition and Supplements. Bone Health & Osteoporosis Foundation. Updated December 27, 2023. Accessed August 22, 2026.
