What is the Medical Name for Vitamin K2?
The medical name for vitamin K2 is menaquinone. Unlike the single compound phylloquinone (vitamin K1), menaquinone is not just one substance but a family of related compounds, or vitamers. These menaquinones are distinguished by the number of isoprene units in their chemical structure, which is denoted as MK-n, where 'n' represents the number of units. The most extensively studied forms are menaquinone-4 (MK-4) and menaquinone-7 (MK-7).
The Menaquinone Family: MK-4 and MK-7
While all menaquinones share a common core structure, their varying side chains give them different properties, including absorption efficiency and availability in the body.
- Menaquinone-4 (MK-4): This form of vitamin K2, also known by the medical name menatetrenone, is unique because it is primarily formed in the body from the conversion of vitamin K1 or a synthetic intermediate called menadione (vitamin K3). MK-4 is found in animal-based products such as eggs, meat, and dairy. It has a shorter half-life in the bloodstream compared to MK-7, requiring more frequent intake to maintain consistent levels. In Japan, a high-dose version of menatetrenone is used as a prescription drug to treat osteoporosis.
- Menaquinone-7 (MK-7): Primarily synthesized by bacteria, this longer-chain menaquinone is found in fermented foods, with the highest concentration occurring in the Japanese dish natto (fermented soybeans). MK-7 has a significantly longer half-life, meaning it remains active in the body for a much longer period than MK-4, making it a highly effective supplemental form.
Beyond Coagulation: The Broader Role of K2
While vitamin K is historically recognized for its role in blood coagulation, vitamin K2 is increasingly appreciated for its pleiotropic (multiple) actions throughout the body. Its primary function involves acting as a cofactor for the enzyme gamma-glutamyl carboxylase (GGCX), which modifies specific proteins to enable them to bind to calcium. These "Gla-proteins" are crucial for a variety of physiological processes.
Vitamin K2's Impact on Bone Health
One of the most significant functions of menaquinone is its impact on bone density. It activates a Gla-protein called osteocalcin, which is produced by osteoblasts (bone-forming cells). Activated osteocalcin is essential for binding calcium to the bone matrix, thereby promoting bone mineralization and increasing bone strength. Research suggests that optimizing vitamin K2 status, particularly with MK-7, is key to maintaining strong bones, especially in postmenopausal women who are at higher risk for osteoporosis.
Vitamin K2 and Cardiovascular Health
Another critical role of vitamin K2 is its ability to prevent the calcification of soft tissues, particularly in blood vessels and arteries. Menaquinone activates matrix Gla protein (MGP), an inhibitor of soft tissue calcification. When vitamin K2 status is low, MGP remains inactive, allowing calcium to deposit in arterial walls, which contributes to arterial stiffness and cardiovascular disease. By activating MGP, menaquinone helps protect against this dangerous buildup.
Comparison: Vitamin K1 (Phylloquinone) vs. Vitamin K2 (Menaquinone)
| Feature | Vitamin K1 (Phylloquinone) | Vitamin K2 (Menaquinone) |
|---|---|---|
| Primary Sources | Green leafy vegetables (e.g., kale, spinach, broccoli), some plant oils | Fermented foods (e.g., natto, certain cheeses), animal products (e.g., eggs, meat) |
| Origin | Plant-derived | Primarily bacterial synthesis, except MK-4 |
| Synthesis in body | Converted to MK-4 in animal tissues | Synthesized by gut bacteria (MK-7, MK-8, etc.) and converted from K1 (MK-4) |
| Absorption and Half-Life | Rapidly cleared from the bloodstream (short half-life) | Longer half-life, especially MK-7, allowing for better accumulation in tissues |
| Main Role | Crucial for blood clotting via hepatic (liver) proteins | Important for extra-hepatic (outside the liver) functions, including bone and heart health |
Dietary Sources of Menaquinones
To ensure adequate intake of menaquinones, a diet rich in a variety of these foods is beneficial. The content can vary depending on the specific fermentation process or animal diet.
- Natto: This Japanese fermented soybean product is the richest known dietary source of MK-7.
- Cheeses: Certain types of cheese, particularly hard and fermented varieties like Gouda and aged Cheddar, contain notable amounts of menaquinones.
- Animal products: Egg yolks, chicken liver, and meat provide a source of MK-4. The K2 content in these products is influenced by what the animal was fed.
- Sauerkraut: Traditional fermented sauerkraut can also contain menaquinones synthesized by bacteria during fermentation.
Supplementation Options for Menaquinone
Dietary intake alone may not be enough to reach optimal vitamin K2 levels, especially for individuals not regularly consuming fermented foods like natto. Supplements offer a convenient way to boost menaquinone status. Most supplements provide K2 in the form of MK-4 or MK-7. Due to its superior bioavailability and longer half-life, MK-7 is often the preferred choice for supplementation aimed at improving long-term bone and cardiovascular health. However, it is essential to consult a healthcare provider before taking vitamin K2 supplements, particularly if you are taking blood-thinning medications like warfarin, as vitamin K can interfere with their efficacy. For more detailed information on vitamin K, you can refer to authoritative sources such as the National Institutes of Health Office of Dietary Supplements.
Conclusion: The Importance of Menaquinone
In conclusion, the medical and chemical term for vitamin K2 is menaquinone, a family of fat-soluble compounds with diverse health benefits. While its role in blood clotting is well-established, menaquinone's impact on calcium metabolism for bone mineralization and the prevention of arterial calcification is now widely recognized. With key subtypes like MK-4 and the more bioavailable MK-7, menaquinone is a vital nutrient available from both fermented foods and animal products. Understanding the specific forms and their functions is key to optimizing your intake for better overall health.
