When people think of nutrients that support strong bones, calcium and vitamin D are usually the first to come to mind. But there’s another vital player working quietly in the background: vitamin K. This fat-soluble vitamin doesn’t just help your blood clot properly; it also plays a crucial role in building strong bones and keeping your arteries healthy and flexible.
What many don’t realise is that vitamin K isn’t a single substance but rather a family of related compounds. Each type of vitamin K behaves differently in the body and supports different aspects of our health.
Vitamin K1 and K2: Different Forms, Different Roles
Vitamin K1 for Blood Clotting
Vitamin K1, also known as phylloquinone, is the form most commonly found in the diet. It's abundant in green leafy vegetables like spinach, kale, broccoli and romaine lettuce. Its primary function is to activate proteins in the liver that are essential for blood clotting. Without sufficient vitamin K1, the body cannot produce the clotting factors it needs, which can lead to excessive bleeding. However, vitamin K1 is absorbed rather poorly, particularly when eaten without fat, and is mostly delivered to the liver.
Vitamin K2 for Bones and Arteries
Vitamin K2 has a much broader role in the body. It’s a group of compounds called menaquinones, identified by the length of their side chains, hence names like MK-4, MK-7, MK-8 and so on. K2 helps to regulate where calcium ends up in the body, activating proteins that direct calcium into bones and teeth, and away from arteries and soft tissues. This function makes vitamin K2 crucial not only for maintaining bone density but also for reducing the risk of arterial calcification, a major contributor to cardiovascular disease.
The Importance of Vitamin K2 for Bone and Cardiovascular Health
Two of the most important proteins activated by vitamin K2 are osteocalcin and matrix Gla protein (MGP). Osteocalcin binds calcium into the bone matrix, improving bone strength and structure. MGP, on the other hand, prevents calcium from depositing in the blood vessel walls and soft tissues. In simple terms, K2 ensures that calcium ends up in the right places, strengthening your skeleton rather than hardening your arteries.
Unlike K1, vitamin K2 is not found in most plant foods. Instead, it is present in fermented foods and certain animal products. Natto, a traditional Japanese dish made from fermented soybeans, is by far the richest known source of vitamin K2 in the form of MK-7. Other sources include hard cheeses like Gouda and Edam, which contain MK-8 and MK-9, and animal-based foods such as egg yolks, chicken liver and butter from grass-fed animals, which provide MK-4. However, these dietary sources are not commonly eaten in large amounts in Western diets, which means that some people may not be getting enough vitamin K2.
SUMMARY: The Functions of Vitamin K
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Blood clotting: Vitamin K1 is essential for the synthesis of clotting factors (II, VII, IX and X) in the liver, which are required for normal blood coagulation.
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Bone metabolism: Vitamin K2 activates osteocalcin, a protein that binds calcium to the bone matrix, contributing to normal bone strength and density.
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Prevention of arterial calcification: Vitamin K2 activates matrix Gla protein (MGP), which inhibits the deposition of calcium in blood vessel walls, helping to maintain arterial flexibility.
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Support of normal wound healing: By enabling proper clot formation, vitamin K helps stop bleeding and supports the early stages of wound repair.
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Regulation of calcium distribution: Vitamin K ensures calcium is directed to bones and teeth, and away from soft tissues, organs, and arteries.
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Support for dental health: Through the activation of osteocalcin and other proteins, vitamin K2 contributes to healthy tooth development and maintenance.
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Potential neuroprotective effects: Emerging research suggests vitamin K may support brain health by participating in the synthesis of sphingolipids, though more studies are needed.
Can the Body Convert Vitamin K1 into K2?
There’s a common belief that the body can convert vitamin K1 into K2 as needed, but the reality is more complex. While some conversion may occur, particularly into MK-4, this process is limited and inefficient, and scientists are still working to understand it. Moreover, this conversion doesn’t produce the longer-chain menaquinones like MK-7, which are the most beneficial for bone and cardiovascular health. This means that even if you eat a diet rich in leafy greens, you may still fall short on the forms of vitamin K that protect your bones and arteries.
MK-7: The Ideal Supplement Form of Vitamin K2
Among the various forms of K2, menaquinone-7 (MK-7) stands out for its superior bioavailability and long-lasting effects. MK-7 remains in the bloodstream for up to 72 hours, compared to just a few hours for MK-4. This extended half-life allows MK-7 to build up in the body with daily use, ensuring more consistent activation of the vitamin K-dependent proteins involved in calcium regulation.
In addition to its stability, MK-7 is also better absorbed than other forms, especially when taken with a source of fat. Clinical studies have shown that MK-7 supplementation improves bone mineral density, boosts osteocalcin activity, and reduces arterial stiffness. Unlike MK-4, which requires multiple daily doses to maintain steady levels, MK-7 can be effectively delivered in a convenient once-daily supplement. Most of the research supporting the bone and heart health benefits of vitamin K2 has been conducted using MK-7, adding further weight to its reputation as the most effective form.
Another advantage of MK-7 is that it can be derived from fermented soy (specifically natto), making it suitable for vegans and vegetarians. Many high-quality MK-7 supplements are now available that are soy-free and use chickpea or flower-based fermentation processes instead.
Why 100 microgrammes is the Ideal Dose
While higher doses of MK-7 (such as 180 or even 360 microgrammes) have been studied and found to be safe, a daily dose of 100 microgrammes appears to be the sweet spot for most people. This amount is sufficient to activate both osteocalcin and MGP fully, providing protection for both bones and arteries without the need for megadosing. It also aligns with the doses used in many successful clinical trials, making it a safe and evidence-backed choice for long-term supplementation.
Vitamin K2 works synergistically with vitamin D3, so combining the two in a supplement can enhance the benefits further. Vitamin D increases calcium absorption from the gut, while vitamin K2 ensures that the extra calcium is directed to the right places. If you’re taking a calcium or vitamin D supplement, adding MK-7 can help reduce the risk of calcium ending up in your arteries instead of your bones.
Who Should Consider Supplementing Vitamin K?
Anyone who doesn’t regularly eat natto or other fermented foods may benefit from a vitamin K2 MK-7 supplement. It’s especially relevant for people following a plant-based or low-fat diet, which may be low in both K1 and K2. Those taking calcium or vitamin D, or with a family history of osteoporosis or heart disease, may also benefit from the added protection that MK-7 provides.
A high-quality supplement containing 100 microgrammes of MK-7, ideally in a vegan and allergen-free capsule, taken with a meal containing fat, is a simple and effective way to support long-term bone and cardiovascular health.
VitaBright Vitamin K2 MK-7 Supplements
Vitamin K may not be the most talked-about nutrient, but it plays a vital role in your body’s long-term wellbeing. While vitamin K1 is essential for clotting, it’s vitamin K2, particularly in the MK-7 form, that offers real protection for your bones and heart. Because it’s hard to get enough from diet alone, especially in Western eating patterns, a supplement providing 100 microgrammes of MK-7 is a smart, science-backed choice for daily health maintenance.
