Vitamin K2 is a fat-soluble vitamin, stored in the body’s fatty tissues and liver. It belongs to a group of compounds called menaquinones. The two most recognized forms are menaquinone-4 (MK4) and menaquinone-7 (MK7). These forms differ in their chemical structures, influencing how they are absorbed and utilized.
The Cardiovascular Importance of Vitamin K2
Vitamin K2 plays a significant role in cardiovascular health by regulating calcium. It activates Matrix Gla Protein (MGP), found in soft tissues like arteries, kidneys, and lungs. Activated MGP prevents calcium from depositing in these soft tissues, protecting against arterial calcification.
Arterial calcification is the buildup of calcium salts within blood vessel walls, leading to hardening and reduced elasticity. This process is a strong predictor of cardiovascular events.
By activating MGP, Vitamin K2 directs calcium away from arteries and into bones for mineralization. This addresses the “calcium paradox,” where calcium consumed for bone health can accumulate in arteries if not properly regulated. A deficiency in Vitamin K2 can lead to inactive MGP, associated with increased arterial stiffness and vascular calcification.
Understanding Menaquinone-4 (MK4)
Menaquinone-4 (MK4) is a form of Vitamin K2 with a shorter chemical structure. It has a relatively short half-life, cleared from the bloodstream within six to eight hours. This influences its dosing frequency when supplemented.
MK4 is found in animal products such as meat, eggs, and dairy, particularly from grass-fed animals. It is also the predominant form of Vitamin K2 produced by mammals, including humans, through the conversion of other K vitamins like K1 and MK7. While it is rapidly utilized, MK4 plays a direct role in various tissue-specific processes, including bone health and, to some extent, cardiovascular function.
Understanding Menaquinone-7 (MK7)
Menaquinone-7 (MK7) is another form of Vitamin K2 with a longer chemical side chain. This contributes to its significantly longer half-life, remaining in the bloodstream for up to 72 hours. Its prolonged presence enhances systemic bioavailability.
MK7 is primarily sourced from fermented foods, most notably natto, a traditional Japanese fermented soybean dish. Certain cheeses also contain MK7. Research indicates that MK7 is highly effective in activating Matrix Gla Protein (MGP), which is crucial for reducing arterial stiffness and preventing the progression of arterial calcification. Studies have shown that even relatively small daily doses, such as 45 mcg of MK7, can effectively increase MGP activation for heart health.
MK4 Versus MK7: Which for Heart Health?
When comparing MK4 and MK7 for cardiovascular health, their differences in absorption, bioavailability, and half-life are important considerations. MK4 has a shorter half-life, meaning it is metabolized and cleared from the body more quickly, typically within hours. This rapid clearance suggests that higher and more frequent doses might be necessary to maintain consistent levels for a sustained effect.
Conversely, MK7 boasts a significantly longer half-life, remaining in the bloodstream for up to 72 hours. This extended presence allows for sustained activation of vitamin K-dependent proteins, including Matrix Gla Protein (MGP), which is directly involved in preventing arterial calcification. The longer half-life of MK7 means it can be taken once daily and still provide continuous support for cardiovascular health.
Current scientific understanding generally points to MK7 as being more effective and practical for broad cardiovascular benefits, especially for inhibiting arterial calcification. The Rotterdam Study, a significant population-based study, showed that higher dietary intake of Vitamin K2, specifically menaquinones like MK7, was strongly associated with a reduced risk of arterial calcification and cardiovascular events. While MK4 is naturally present in the body and has its own roles, its rapid metabolism makes it less ideal for sustained systemic effects on arterial health compared to MK7’s prolonged action.