Vitamin K is a fat-soluble nutrient recognized for its involvement in several bodily processes, primarily coagulation. It exists in multiple forms, including Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinone). Vitamin K2 plays an important part in bone and cardiovascular health. Understanding how long a specific form of K2 remains active is important for predicting its effectiveness. The duration of activity, known as the half-life, is a defining characteristic of menaquinone-7 (MK-7).
Understanding the Forms of Vitamin K2
Vitamin K2 consists of compounds known as menaquinones, designated by an MK-n number representing the length of the molecule’s side chain. The two forms most often discussed in supplementation are menaquinone-4 (MK-4) and menaquinone-7 (MK-7). These two forms differ significantly in their source and how the body handles them.
MK-4 is the shorter-chain form, primarily found in animal products like meat, eggs, and high-fat dairy. MK-4 is rapidly absorbed but also very quickly cleared from the circulation dueence to its short side chain. MK-7 is a long-chain menaquinone derived largely from bacterial fermentation, such as Natto. The longer, more complex chemical structure of MK-7 is responsible for its unique behavior, setting it apart from the short-acting MK-4.
The Extended Half-Life of MK-7
The most distinctive feature of menaquinone-7 is its significantly extended half-life compared to other K vitamins. The half-life is the time it takes for the concentration of a substance in the blood plasma to be reduced by half. For MK-7, this duration is approximately 68 hours, which is close to three full days.
This prolonged presence in the bloodstream results from the long isoprenoid side chain of the MK-7 molecule. This structure makes MK-7 highly lipophilic, allowing it to be incorporated into and circulated within low-density lipoproteins (LDL). By circulating in the LDL fraction, MK-7 is delivered throughout the body to extrahepatic tissues. This includes the bones and arterial walls, where Vitamin K2 performs its most important functions. In contrast, the shorter-chain MK-4 is cleared much faster, with a half-life of only a few hours. Following a single dose, MK-7 remains detectable in the plasma for up to 96 hours.
Functions Supported by Long-Term Presence
The prolonged circulating time of MK-7 is highly beneficial because the biological processes it supports require a continuous, steady supply of the vitamin. Vitamin K2 acts as a cofactor for an enzyme that activates a group of proteins known as Vitamin K-dependent proteins (VKDPs). These proteins are synthesized in an inactive form and must be activated by K2 to perform their function.
One of these VKDPs is Matrix Gla Protein (MGP), found in the walls of arteries. MGP is a strong inhibitor of soft-tissue calcification. MGP activation is necessary to regulate calcium and prevent it from depositing in the blood vessel walls, a process associated with arterial stiffness. The continuous presence of MK-7 ensures that MGP is constantly activated, maintaining healthy calcium dynamics.
Another VKDP is Osteocalcin, produced by bone-forming cells (osteoblasts). Once activated by K2, Osteocalcin binds calcium and integrates it into the bone matrix, supporting bone mineralization and strength. Because both the cardiovascular and skeletal systems require continuous protein activation, the extended half-life of MK-7 provides a persistent biological signal active across both systems simultaneously.
Applying the Half-Life to Supplementation Frequency
The long half-life of menaquinone-7 simplifies the practical application of supplementation. Since the vitamin remains in the circulation for multiple days, a once-daily dose of MK-7 is sufficient to maintain consistent, elevated blood plasma levels. This daily consistency ensures that the body reaches a “steady state,” where the rate of intake balances the rate of clearance.
At this steady state, there is a continuous pool of active MK-7 available to fully activate the MGP and Osteocalcin proteins. For optimal absorption, MK-7 supplements are recommended to be taken with a meal that contains some dietary fat, leveraging its fat-soluble nature. Once-daily dosing significantly improves compliance for long-term health goals.