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16th Feb 2024

How Does Vitamin K2 Affect Calcium Absorption?

Posted by Melanie Winter

Vitamin K is a name given to a group of fat-soluble vitamins. The original term vitamin “K” comes from the K in the German word Koagulation, meaning the ability to clot blood or prevent bleeding.

There are two types of vitamin K:

  • Vitamin K1 (phylloquinone) found in leafy greens and plant food
  • Vitamin K2 (menaquinones) produced by gut bacteria and in some animal and fermented foods (like Natto and some cheeses).

Vitamin K2 menaquinones can be further subdivided and are numbered MK-4 through MK-13 based on their chemical structure. Research has shown the MK-7 version of vitamin K2 is absorbed the best, and this form is often used in vitamin K2 supplements.

The differences in actions between vitamin K1 and vitamin K2 are as widely contrasting as the dietary sources they are concentrated in. Vitamin K1 can be converted to vitamin K2 in the gut with microbiota. However, only 20% of vitamin K1 is absorbed and the conversion rate of vitamin K1 to vitamin K2 is only 5-25%.

What’s the difference between vitamin K1 and K2:

  • The liver utilizes vitamin K1 - found in nature as phylloquinones from dark leafy greens – to initiate a blood-clotting cascade.
  • Vitamin K2 is primarily used in other body sites to aid in correctly placing Calcium.

How does vitamin K2 affect Calcium absorption:

There are two areas where vitamin K2 affects calcium absorption and utilisation.

1. Cardiovascular health:

Vitamin K2 inhibits arterial calcification and stiffening by inhibiting calcium deposits on the artery walls. Vitamin K2 activates a substance called matrix GLA protein (MGP). MGP works by reducing how much calcium is deposited on artery walls. So, a diet deficient in vitamin K can result in reduced activation of MGP, which slows calcium removal from the artery walls. When the blood vessels have calcification or calcium build up, it makes these vessels less elastic and contributes to plaque building up, which can increase the risk of cardiovascular disease.

2. Bone health:

As mentioned above, regarding cardiovascular health, vitamin K2 activates a protein called MGP. Activated MGP helps prevent calcium from ending up in the wrong places, like your arteries, and instead directs it to where it's needed—in your bones and teeth.

The osteoblasts (found in our bone tissue) produce osteocalcin, which helps take the calcium from the blood and get it to the bone matrix. The newly made osteocalcin, though, is inactive and needs vitamin K2 so it can bind to calcium.

In simple terms, osteoblasts build new bone with the help of calcium, osteoclasts break down old or damaged bone, and vitamin K2 ensures that the calcium goes to the right places—your bones and teeth—by activating proteins like MGP.

What is the ‘calcium paradox’?

The "calcium paradox" refers to a situation where it is thought that increased calcium intake, especially in the form of supplements, may lead to negative health outcomes such as arterial calcification and an increased risk of cardiovascular events. This paradox arises because while calcium is essential for various physiological functions, its deposition in soft tissues, such as arteries, can be detrimental.

Vitamin K2 plays a crucial role in calcium metabolism and helps address the calcium paradox.

‘Bone/vascular crosstalk’

For many years, it has been thought that osteoporosis (low calcium deposition in bones) and vascular calcification (excess calcium in artery walls) were unrelated to age-dependent processes. However, many studies now support that there could be a link between these two processes that affect calcium placement.

In the Framingham, Women's Health Across the Nation (SWAN), Multi-Ethnic Study of Atherosclerosis (MESA), and Rotterdam studies, a correlation was observed between the decline in bone mineral density (BMD) and the advancement of aortic calcification, along with an elevated likelihood of cardiovascular disease (CVD) mortality.

What does this mean?

Emerging research shows that vitamin K2 may be the link to solving the problem of two concerns in modern-day health. The ‘Calcium paradox’ where the calcium is not getting into the bones but rather clogging the arteries.

More research is needed and there are other factors that will come into it. But for now, vitamin K2 is a promising nutrient that can help be the traffic director that moves calcium into bones and away from arteries.

Key takeaways

  • Osteoporosis is characterised by low calcium deposits into the bone, which affects bone density and strength.
  • Vascular calcification- is where calcium can build up in arteries, leading to them getting blocked and causing an increased risk of cardiovascular disease.
  • Vitamin K2 can regulate proteins such as osteocalcin and GMP, which then go on to regulate how the bones use calcium and whether calcium ends up in the blood vessels instead.
  • Vitamin K2 is hard to obtain from the diet and is available in supplement form, with the highest bioavailable form being a patented ingredient called MK-7 or MenaQ7®

*Information in this blog is not intended to take the place of any medical information and is not intended to diagnose or treat any medical conditions. 

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