Menaquinone-7: The Scientific Identity of K2-7
Vitamin K2-7 is not its scientific name but a common shorthand for its specific subtype. The proper scientific designation is menaquinone-7, which is often abbreviated as MK-7. The number '7' refers to the length of its chemical side chain, which is composed of seven repeating isoprene units. This longer side chain is responsible for MK-7's distinct properties, including its enhanced bioavailability and longer half-life in the body compared to other forms, such as MK-4.
The Importance of MK-7's Structure and Bioavailability
The structural difference between MK-7 and other forms of vitamin K is significant. While vitamin K1 (phylloquinone) is mainly involved in blood clotting in the liver, MK-7 circulates longer in the bloodstream and is more readily available to extrahepatic tissues, such as bones and arteries. This allows it to activate vital proteins in these areas, ensuring calcium is utilized properly. MK-7 is primarily produced by bacteria, notably Bacillus subtilis natto during the fermentation process of soybeans to make the Japanese dish, natto.
How MK-7 Activates Critical Proteins
The primary function of MK-7 is to serve as a cofactor for an enzyme called gamma-glutamyl carboxylase. This enzyme converts specific protein-bound glutamate residues into gamma-carboxyglutamate (Gla) residues. The Gla residues are then able to bind calcium ions, triggering the proteins' biological functions. Two of the most important Gla-containing proteins activated by MK-7 are:
- Osteocalcin: Produced by bone-building cells called osteoblasts, this protein helps bind calcium to the bone matrix, improving bone density and strength.
- Matrix Gla Protein (MGP): Synthesized in cartilage and the walls of blood vessels, MGP is a potent inhibitor of soft-tissue calcification. By activating MGP, MK-7 helps prevent calcium from depositing in arteries and other inappropriate locations.
Comparing Different Forms of Vitamin K
Understanding the differences between vitamin K1 and the various subtypes of K2 is essential for appreciating MK-7's role. While all K vitamins share a core function in blood coagulation, their absorption, half-life, and biological activity in non-liver tissues can differ significantly.
| Feature | Vitamin K1 (Phylloquinone) | Vitamin K2 (MK-4) | Vitamin K2 (MK-7) |
|---|---|---|---|
| Primary Source | Green leafy vegetables | Animal products, synthesized by mammals | Fermented foods, especially natto |
| Origin | Plant-based | Animal-based/Conversion from K1 | Bacterial Fermentation |
| Half-Life in Blood | Short (hours) | Short (hours) | Long (days) |
| Bioavailability | Lower absorption | Variable, cleared quickly | Higher and more sustained |
| Main Function | Blood clotting in liver | Some bone and cardiovascular support | Strong bone and cardiovascular support |
| Mechanism | Works systemically via liver | Acts locally in tissues | Systemic, long-lasting effect |
Dietary Sources of Menaquinone-7
The availability of Menaquinone-7 in the typical Western diet is limited, with the richest source being the traditional Japanese fermented soybean dish, natto. Other fermented foods and aged cheeses also contain some MK-7, but at much lower concentrations. This is a key reason why many individuals in Western countries may have suboptimal vitamin K2 levels, even with adequate intake of vitamin K1 from vegetables. The production of MK-7 by gut bacteria is often not sufficient for optimal extrahepatic function.
Health Benefits Associated with MK-7
Decades of research have highlighted MK-7's potential health benefits, primarily through its ability to regulate calcium distribution in the body. The positive impacts on bone and cardiovascular health are particularly well-documented.
Cardiovascular Health
Calcium accumulation in the arteries is a significant risk factor for heart disease. MK-7 activates Matrix Gla Protein (MGP), which inhibits calcium deposits in arterial walls, promoting more flexible and healthier blood vessels. Observational studies have shown that a higher intake of menaquinones (vitamin K2) is associated with a lower risk of coronary heart disease.
Bone Health
For bone health, MK-7 activates osteocalcin, directing calcium to be integrated into the bone matrix. This process is crucial for maintaining and increasing bone mineral density, especially in postmenopausal women who are at higher risk for osteoporosis. Multiple studies have shown that MK-7 supplementation can improve bone strength and reduce the risk of fractures. The synergistic relationship with Vitamin D is also critical; Vitamin D aids calcium absorption, while MK-7 ensures it is properly utilized by the bones.
Conclusion
In summary, vitamin K2 7 is most accurately referred to by its scientific name, menaquinone-7 (MK-7). This unique subtype of vitamin K2 is distinguished by its long chemical side chain, which provides superior bioavailability and a longer half-life compared to other forms like MK-4 and K1. Its critical role in activating proteins such as osteocalcin and Matrix Gla Protein is fundamental to maintaining both strong, healthy bones and flexible, calcification-free arteries. While primarily found in fermented foods like natto, its scarcity in the average Western diet makes supplementation a common approach for optimizing intake. Recognizing MK-7's distinct properties and its profound impact on calcium metabolism underscores its importance for overall health, particularly bone and cardiovascular wellness. [Find more comprehensive information on the physiological importance of vitamin K on the National Institutes of Health website]
