What does Vitamin K2 do?

When most people think of Vitamin K, they picture blood clotting. That’s true of Vitamin K1, which you’ll find in leafy greens like spinach and kale. But Vitamin K2 is the lesser-known partner in the family - and it does far more than most realise.

Vitamin K2 plays a unique role in calcium metabolism. It activates proteins that help transport calcium into bones and teeth where it belongs, while preventing calcium from being deposited in soft tissues like arteries. ¹ Without enough K2, calcium can end up in the wrong places, which may affect bone strength and cardiovascular health over time.

Vitamin K2 and bone health

One of the most important things Vitamin K2 does is support bone mineralisation. It activates a protein called osteocalcin, which binds calcium to the bone matrix. ² Think of it like a construction worker ensuring building materials go exactly where they’re needed.

Research suggests that adequate Vitamin K2 may improve bone density and reduce fracture risk, especially when paired with Vitamin D3, which improves calcium absorption in the gut. ³ This duo - Vitamin D3 and K2 - is often recommended together because they work synergistically to strengthen bones and teeth.

Vitamin K2 and heart health

Another standout benefit of K2 is its role in protecting the arteries. K2 activates a protein called matrix GLA-protein (MGP), which helps prevent calcium from depositing in blood vessel walls. ⁴ When calcium builds up in the arteries, it leads to stiffness and narrowing, increasing cardiovascular risk.

By keeping calcium in the right places, Vitamin K2 may help maintain flexible, healthy arteries and long-term cardiovascular wellbeing. Studies show that diets higher in K2 are linked with a reduced risk of arterial calcification and heart disease. ⁵

K1 vs K2: What’s the difference?

Both K1 and K2 belong to the same vitamin family, but their roles and sources differ.

Vitamin K1 is found in leafy green vegetables and is primarily involved in blood clotting.
Vitamin K2 is found in fermented foods, animal products and certain supplements. Its main roles are calcium distribution, bone health, and cardiovascular support.

Because K2 is less common in modern diets, many people may not get enough - especially if they don’t eat traditional fermented foods like natto (a Japanese dish made from fermented soybeans) or certain cheeses.

Best sources of Vitamin K2

If you want to increase your K2 intake naturally, here are some foods to focus on:

Natto (the richest source, though not everyone enjoys its strong taste)
Hard cheeses and some soft cheeses
Egg yolks
Chicken, especially dark meat
Beef liver

Even with these foods, it can still be tricky to get enough K2 daily, which is why many people choose a Vitamin K2 supplement, often in the MK-7 form for its superior absorption and longer activity in the body. ⁶

Why Vitamin K2 works best with Vitamin D3

If you’re already taking Vitamin D3 for immune and bone health, adding Vitamin K2 makes a lot of sense. Vitamin D helps your body absorb calcium, while Vitamin K2 ensures that calcium ends up in the right places. Without K2, there’s a risk that extra calcium may not be directed properly.

That’s why many supplements now combine Vitamin D3 and K2 into a single formula - supporting stronger bones, healthier teeth, and long-term cardiovascular protection.

Signs you might not be getting enough

Vitamin K2 deficiency isn’t always obvious, but low levels may contribute to:

Weaker bones or reduced bone density
Arterial stiffness or calcification
Poor dental health (since teeth rely on calcium too)

Because K2 is not widely available in many diets, it’s worth considering a supplement if you don’t regularly consume fermented foods or certain animal products.

So, what does Vitamin K2 do? Quite a lot. From strengthening bones to protecting your arteries, K2 is the unsung nutrient that works hand in hand with Vitamin D3 to direct calcium where it’s needed most.

If you’re serious about bone and heart health, or if your diet lacks fermented foods, adding a Vitamin K2 supplement could make a meaningful difference. It may not be as famous as Vitamin C or D, but its role in long-term wellbeing is just as vital.