What is the other name for vitamin K2?

December 8, 2025 •

3 min read

While many know that vitamin K is essential for blood clotting, far fewer are aware that it actually comes in two primary forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). These two types work differently in the body and are found in different food sources, but confusion over their nomenclature is common.

Quick Summary

The other name for vitamin K2 is menaquinone, a fat-soluble nutrient that includes several subtypes like MK-4 and MK-7. It plays a key role in distributing calcium to bones and keeping it from arteries. Sources include fermented foods and some animal products, distinguishing it from plant-based vitamin K1.

Key Points

Menaquinone is Vitamin K2: The alternative name for vitamin K2 is menaquinone, a family of fat-soluble compounds that include different subtypes.
Subtypes MK-4 and MK-7: The most prominent forms of menaquinone are MK-4, found in animal products, and MK-7, derived from fermented foods.
Longer-Lasting Effect: MK-7, in particular, has a longer half-life and higher bioavailability compared to MK-4 and vitamin K1, making it more effective for extrahepatic tissues.
Key for Bone and Heart Health: Unlike K1, menaquinone is crucial for activating proteins that direct calcium to your bones and prevent it from depositing in your arteries.
Food Sources Vary: Vitamin K1 comes mainly from plants, while menaquinone comes from fermented foods like natto and animal products such as eggs and certain cheeses.

The other name for vitamin K2 is menaquinone. This name refers to a family of fat-soluble compounds, known scientifically as menaquinones, which are characterized by a varying number of isoprenoid residues in their side chain. While phylloquinone (vitamin K1) is primarily involved in blood coagulation, menaquinones play a more significant role in bone and cardiovascular health by directing calcium deposition.

Menaquinones: The Subtypes of Vitamin K2

There isn't just one type of menaquinone, but rather a series of related compounds identified by the number of isoprenoid units in their side chain (e.g., MK-4, MK-7, MK-8). The two most researched and significant subtypes are MK-4 and MK-7.

Menaquinone-4 (MK-4)

This short-chain menaquinone is found predominantly in animal products. The body can also convert some dietary vitamin K1 into MK-4 in certain tissues. However, MK-4 has a very short half-life, meaning it is quickly cleared from the body, necessitating more frequent intake for sustained benefit.

Sources of MK-4 include:

Goose liver pâté
Egg yolks
Grass-fed butter and dairy
Certain organ meats, like chicken liver

Menaquinone-7 (MK-7)

In contrast, MK-7 is a long-chain menaquinone that is more efficiently absorbed and has a much longer half-life, remaining in the bloodstream for a longer period. It is primarily synthesized by bacteria during the fermentation process.

Sources of MK-7 include:

Natto (fermented soybeans) – an especially rich source
Sauerkraut
Some fermented cheeses, such as Gouda

The Difference Between Vitamin K1 and Vitamin K2 (Menaquinone)

Understanding the distinction between vitamin K1 and vitamin K2 is crucial for grasping their unique roles in the body. While both are part of the vitamin K family, they differ significantly in their sources, functions, and bioavailability.


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinone)
Primary Sources	Leafy green vegetables (kale, spinach, broccoli), certain plant oils	Fermented foods (natto, cheese), animal products (egg yolks, liver)
Synthesized by	Plants during photosynthesis	Bacteria, including gut microflora; some animal tissue conversion
Primary Function	Blood clotting via activation of liver coagulation proteins	Directing calcium; bone mineralization (osteocalcin), arterial calcification prevention (MGP)
Bioavailability	Lower bioavailability, especially from plants; quickly cleared by the body	Higher bioavailability, especially MK-7, which has a long half-life
Subtypes	One main form, phylloquinone	Multiple forms, MK-4 and MK-7 being the most studied

Health Benefits Associated with Vitamin K2

Research continues to reveal the importance of menaquinone beyond its basic role in vitamin K activity. Its longer half-life and unique functionality make it particularly beneficial for certain processes.

Bone Health

Vitamin K2 activates osteocalcin, a protein that binds calcium to the bone matrix, promoting bone formation and mineralization. Studies have shown that supplementation with vitamin K2 can improve bone mineral density and reduce fracture risk, particularly in postmenopausal women. It works synergistically with vitamin D and calcium for optimal skeletal health.

Heart Health

One of the most notable benefits of vitamin K2 is its role in cardiovascular health. It activates Matrix Gla Protein (MGP), which helps prevent the calcification of arteries and soft tissues. Higher dietary intake of vitamin K2 has been associated with a reduced risk of coronary heart disease.

Conclusion

In summary, the other name for vitamin K2 is menaquinone, encompassing a variety of subtypes such as MK-4 and MK-7. Unlike vitamin K1, which is found in leafy greens and primarily functions in blood clotting, menaquinone is sourced from fermented and animal foods and is essential for properly directing calcium in the body. Its longer-lasting presence in the bloodstream, particularly in the MK-7 form, makes it a potent nutrient for maintaining bone strength and preventing arterial calcification. For individuals looking to support these specific health areas, ensuring adequate intake of menaquinone through diet or supplementation is beneficial, especially when combined with vitamin D and calcium.

This article provides general information and is not a substitute for professional medical advice. Always consult with a healthcare provider before starting any new supplement regimen. For more details on vitamin K, see the NIH Office of Dietary Supplements fact sheet.

Frequently Asked Questions

The main difference is their source and function. Vitamin K1 (phylloquinone) is found in plants and primarily supports blood clotting. Vitamin K2 (menaquinone) comes from fermented and animal foods and plays a key role in bone and cardiovascular health by regulating calcium.

Menaquinone-7 (MK-7) is a specific subtype of vitamin K2. Vitamin K2 is a broader term encompassing all menaquinones, including MK-4, MK-7, and others.

The richest source of MK-7 is natto (fermented soybeans). Other good sources include some hard cheeses, egg yolks (MK-4), and liver.

Yes, the body can convert some vitamin K1 to MK-4 in certain tissues, but this conversion is not always efficient enough to produce optimal levels of vitamin K2 for benefits beyond basic blood clotting.

Yes, menaquinone is known to work synergistically with vitamin D3 to regulate calcium metabolism. Vitamin D is responsible for absorbing calcium, while vitamin K2 helps ensure that calcium is deposited in the proper places, like bones, and not in arteries.

While generally safe, individuals taking blood-thinning medication (like warfarin) should consult a doctor before taking any vitamin K supplement, including menaquinone, as it could interfere with the medication's effectiveness.

MK-7 is preferred because it has a significantly longer half-life than MK-4, meaning it remains active in the body for a longer time. This allows it to reach non-liver tissues, such as bones and arteries, more effectively.