What is Vitamin K2?
Vitamin K is a family of fat-soluble vitamins known for their crucial role in blood clotting, a function primarily performed by Vitamin K1 (phylloquinone). However, Vitamin K2, or menaquinone, is increasingly recognized for its distinct and vital functions in supporting bone and cardiovascular health by regulating calcium. While K1 is found in leafy greens, K2 is primarily found in fermented foods and certain animal products. Unlike K1, K2 has a longer half-life and broader systemic effects beyond the liver, influencing tissues like bones, cartilage, and arteries.
The Two Main Forms: MK-4 and MK-7
The most common and well-researched forms of vitamin K2 are menaquinone-4 (MK-4) and menaquinone-7 (MK-7). The key difference between these menaquinones lies in the length of their side chain, which influences their absorption, transportation, and longevity within the body. While MK-4 is the predominant form found in certain tissues, MK-7 is the form that demonstrates superior bioavailability and duration of action in the bloodstream, making it a more effective choice for supplementation.
Why MK-7 is Considered the Most Active Form
The debate between which form of vitamin K2 is 'most active' often centers on bioavailability and half-life. While some argue that MK-4 is more active because it's found in the body's tissues, MK-7's unique properties make it a far more efficient and superior form for systemic health benefits, particularly in supplement form.
Superior Bioavailability and Longevity
MK-7 is much better absorbed and remains in the bloodstream for a significantly longer period than MK-4, with a half-life of up to 72 hours compared to MK-4's mere 6-8 hours. This extended availability allows MK-7 to continuously support the activation of vitamin K-dependent proteins throughout the body with a single daily dose, unlike the larger, multiple doses required for MK-4 supplements.
The "All-Trans" Advantage
The chemical structure of MK-7 also matters, as it can exist in both cis and trans isomers. The all-trans isomer is the biologically active form, and high-quality supplements utilize this specific version for maximum efficacy. This ensures the body can efficiently use the nutrient to activate proteins like osteocalcin and Matrix Gla Protein (MGP).
Key Health Benefits Driven by MK-7
Optimal Bone Health and Density
Vitamin K2, and specifically the MK-7 form, is a crucial partner to Vitamin D3 and calcium for building and maintaining strong bones. MK-7 activates osteocalcin, a protein that binds calcium and integrates it into the bone matrix, improving bone mineral density and reducing the risk of fractures. This process is critical for preventing osteoporosis, especially in at-risk populations like postmenopausal women.
Cardiovascular Protection
MK-7 plays a significant role in preventing arterial calcification, a major risk factor for heart disease. It activates Matrix Gla Protein (MGP), a potent inhibitor of calcium accumulation in soft tissues like artery walls. By helping to direct calcium to the bones and away from the arteries, MK-7 supports arterial elasticity and overall cardiovascular health.
Other Emerging Benefits
Research also indicates that MK-7 may have broader health implications. Studies suggest potential benefits for brain health, insulin sensitivity, and anti-inflammatory properties, though more research is ongoing.
Comparing MK-4 and MK-7
| Feature | Menaquinone-4 (MK-4) | Menaquinone-7 (MK-7) |
|---|---|---|
| Source | Produced by mammals from K1, found in animal products (e.g., egg yolks, liver, dairy). | Produced by bacteria, found primarily in fermented foods like natto and certain cheeses. |
| Half-Life | Very short (approx. 6-8 hours). | Long (approx. 72 hours). |
| Bioavailability | Lower bioavailability, requiring high, multiple daily doses to maintain consistent levels. | Highly bioavailable and accumulates in the bloodstream with regular, small daily doses. |
| Primary Supplement Form | Less common due to short half-life and higher dose requirement. | Dominant form in supplements due to superior efficacy and convenience. |
| Distribution | Rapidly absorbed into tissues and organs. | Circulates in the bloodstream longer, allowing broader tissue distribution. |
Getting Vitamin K2: Food Sources vs. Supplements
Dietary intake of vitamin K2, especially the highly bioavailable MK-7, is typically insufficient in Western diets. While foods like natto, hard cheeses, and grass-fed animal products contain K2, the amounts are often low or the food is not part of a regular diet. Therefore, supplementation, preferably with a high-quality all-trans MK-7, is often necessary to achieve optimal levels and reap the full benefits for bone and heart health. For optimal absorption, it is important to take fat-soluble vitamins like K2 with a meal containing some fat.
Conclusion: Choosing the Right K2
When assessing what is the most active form of vitamin K2, the evidence clearly points to Menaquinone-7 (MK-7) as the most effective option for supplementation. Its longer half-life, superior bioavailability, and proven benefits for bone and cardiovascular health make it the preferred choice for those looking to support their body's optimal calcium utilization. While MK-4 has its own role, its limitations in supplemental form make MK-7 the more practical and efficient alternative for consistent, systemic benefits. For those with bone or heart health concerns, ensuring adequate intake of MK-7 through a high-quality supplement is a straightforward and impactful strategy.
For more clinical insights on the benefits of MK-7, refer to publications on MenaQ7, a well-researched branded form of vitamin K2 (MK-7).
