What is the use of vitamin K2?

October 1, 2025 •

3 min read

While most people know about the importance of vitamins like C and D, the roles of vitamin K, particularly its K2 form, are less commonly understood. In fact, vitamin K2 is now considered a vital player in bone and cardiovascular health, activating proteins that manage calcium throughout the body to ensure it is deposited in the right places, like your bones, rather than in your arteries.

Quick Summary

Vitamin K2, or menaquinone, is a fat-soluble vitamin that activates proteins responsible for regulating calcium metabolism, contributing significantly to bone and cardiovascular health. It helps direct calcium into bones while preventing its accumulation in soft tissues like arteries and kidneys.

Key Points

Manages Calcium Distribution: Vitamin K2 activates proteins like osteocalcin and MGP, directing calcium to bones and teeth while preventing buildup in arteries and soft tissues.
Supports Bone Health: By activating osteocalcin, vitamin K2 helps incorporate calcium into the bone matrix, promoting stronger, denser bones and reducing fracture risk, particularly in those with osteoporosis.
Protects Cardiovascular Health: Vitamin K2 helps prevent vascular calcification by activating MGP, an inhibitor of arterial plaque formation, which can reduce the risk of coronary heart disease.
Found in Specific Foods: Rich sources of vitamin K2 include fermented foods like nattō and certain cheeses, as well as animal products such as egg yolks and liver.
Differs from Vitamin K1: Unlike K1, which is primarily used for blood clotting in the liver, vitamin K2 has a longer half-life and greater bioavailability for extra-hepatic tissues, including bones and arteries.
Caution with Medications: Individuals taking blood-thinning medications, like warfarin, must consult a doctor before supplementing with vitamin K2, as it can affect coagulation.

The Primary Functions of Vitamin K2

At its core, the main use of vitamin K2 is to activate specific proteins that manage calcium in the body. This crucial function helps prevent calcium from building up in places it shouldn't, such as the arteries and other soft tissues, and ensures it is properly utilized where it's needed most—in the bones and teeth. Two key proteins activated by vitamin K2 are:

Osteocalcin: Produced by bone-building cells (osteoblasts), this protein requires vitamin K2 to bind calcium to the bone matrix, reinforcing bone density and strength.
Matrix Gla Protein (MGP): Found in the walls of blood vessels, MGP is a potent inhibitor of soft tissue calcification. Vitamin K2 activates MGP, which in turn helps prevent calcium from forming dangerous plaques in your arteries.

Benefits for Bone and Cardiovascular Health

Research has highlighted vitamin K2's specific benefits beyond the basic function of blood clotting, which is primarily handled by vitamin K1. Its extra-hepatic activity (outside the liver) and longer half-life mean it remains in circulation longer, benefiting tissues like bone and arteries.

Bone Health: Low levels of vitamin K have been associated with a higher risk of fractures. Some studies, particularly those conducted in Japan, have even shown that K2 supplementation can significantly reduce the risk of vertebral and hip fractures in postmenopausal women.

Cardiovascular Health: Vascular calcification, or the hardening of arteries due to calcium buildup, is a major risk factor for heart disease. A landmark study, known as the Rotterdam Study, found that a higher intake of vitamin K2, but not K1, was associated with a reduced risk of coronary heart disease and severe aortic calcification.

Comparing Vitamin K1 and Vitamin K2

Though part of the same vitamin family, K1 and K2 have distinct sources, absorption rates, and functions in the body. Understanding these differences is key to appreciating the specific use of vitamin K2.


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Sources	Leafy green vegetables (kale, spinach), broccoli, vegetable oils.	Fermented foods (nattō, sauerkraut), animal products (egg yolks, liver, grass-fed butter), and certain cheeses (Gouda, Brie).
Absorption	Less readily absorbed; rapidly filtered by the liver for blood clotting.	Better absorbed and remains in circulation for a longer duration.
Primary Function	Cofactor for blood clotting factors in the liver.	Extra-hepatic activity, primarily activating proteins for calcium distribution in bone and arteries.
Bioavailability	Lower bioavailability and shorter half-life.	Higher bioavailability, especially long-chain menaquinones like MK-7, allowing it to reach and benefit soft tissues.

Sources of Vitamin K2

While vitamin K1 is abundant in the modern Western diet, vitamin K2 is more difficult to obtain in significant amounts from common foods. The richest dietary source is nattō, a traditional Japanese fermented soybean product, which is high in the MK-7 subtype. Other sources include:

MK-4: Found in animal-based foods, such as egg yolks and liver.
MK-7, MK-8, and MK-9: Predominantly found in fermented foods like certain cheeses (Gouda, Edam) and sauerkraut.
Supplementation: Given the challenges of obtaining sufficient K2 from diet alone, especially for those who don't eat fermented foods, supplementation with MK-4 or MK-7 is common. These are often paired with vitamin D3, as the two vitamins work synergistically to support bone and cardiovascular health.

Potential Interactions and Precautions

Despite its promising benefits, some precautions are necessary, particularly for individuals on blood-thinning medications. Vitamin K plays a vital role in blood coagulation, and increasing your intake, especially through supplements, can interfere with the effectiveness of these drugs. It is crucial to consult a healthcare provider before starting any vitamin K2 supplementation, particularly if you are on medications like warfarin.

Conclusion

In summary, the use of vitamin K2 extends far beyond simple blood clotting. By activating key proteins that regulate calcium, it plays a critical role in supporting strong bones and healthy, flexible arteries. While food sources exist, they are not always sufficient, making supplementation a popular option. However, given its impact on blood coagulation, it is essential to seek medical advice before beginning a supplement regimen. This powerful, fat-soluble vitamin is increasingly recognized for its contribution to long-term health and wellness.

Reference: For more detailed scientific research on vitamin K2's health effects, you can visit the following Open Access Journal article.

Frequently Asked Questions

Vitamin K2 activates specific proteins that regulate calcium in the body. It helps properly integrate calcium into bone tissue while simultaneously preventing calcium from depositing in arteries and other soft tissues, promoting both bone and cardiovascular health.

Vitamin K1 (phylloquinone), found in leafy greens, is primarily used by the liver for blood clotting. Vitamin K2 (menaquinone), found in fermented foods and animal products, has a longer half-life and greater bioavailability, primarily benefiting extra-hepatic tissues like bones and blood vessels.

The best sources of vitamin K2 include fermented foods like nattō (fermented soybeans) and sauerkraut, hard and soft cheeses, egg yolks, liver, and grass-fed butter.

While it is possible to get some vitamin K2 from diet, it is often difficult to get a sufficient amount from typical Western diets, as the richest sources (like nattō) are not common staples. Supplements are a common way to increase intake.

Vitamin K2 supplementation may be beneficial for bone and heart health, but it is important to speak with a healthcare provider first. This is especially true if you are taking blood-thinning medications, as vitamin K can interfere with their function.

The most well-researched forms are MK-4 and MK-7. MK-7 generally has higher bioavailability and a longer half-life, meaning it stays in your system longer to benefit soft tissues. However, the best type for you can depend on your specific health goals.

While promising observational studies, such as the Rotterdam Study, show a strong correlation between higher vitamin K2 intake and a reduced risk of coronary heart disease and vascular calcification, more long-term controlled trials are still needed to confirm its effectiveness in prevention.